Chapter LXVII: Management (1)

The term "management," broadly speaking, includes not only the actual skilled attention necessary for the proper operation of the machines, after the plant is built, but also other duties which must be performed from its inception to completion, and which may be classified as

1. Selection;
2. Location;
3. Erection;
4. Testing;
5. Running;
6. Care;
7. Repair.

That is to say, someone must select the machinery, determine where each machine is to be located, install them, and then attend to the running of the machines and make any necessary repairs due to the ordinary mishaps likely to occur in operation.

These various duties are usually entrusted to more than one individual; thus, the selection and location of the machinery is done by the designer of the plant, and requires for its proper execution the services of an electrical engineer, or one possessing more than simply a practical knowledge of power plants.

The erection of the machines is best accomplished by those making a specialty of this line of work, who by the nature of the undertaking acquire proficiency in methods of precision and an appreciation of the value of accuracy which is so essential in the work of aligning the machines, and which if poorly done will prove a constant source of annoyance afterward.

The attention required for the operation of the machines, embracing the running care and repair, is left to the "man in charge," who in most cases of small and medium size plants is the chief steam engineer. He must therefore, not only understand the steam apparatus, but possess sufficient knowledge of electrical machinery to operate and maintain it in proper working order.

The present chapter deals chiefly with alternating current machinery, the management of direct current machines having been fully explained in Guide No. 3, however, some of the matter here presented is common to both classes of apparatus.

* * * * *

=Selection.=--In order to intelligently select a machine so that it will properly harmonize with the conditions under which it is to operate, there are several things to be considered.

1. Type;
2. Capacity;
3. Efficiency;
4. Construction.

The general type of machine to be used is, of course, dependent on the system employed, that is, whether it be direct or alternating, single or polyphase.

Thus, the voltage in most cases is fixed except on transformer
systems where a choice of voltage may be had by selecting a
transformer to suit.

In alternating current constant pressure transmission circuits, an average voltage of 2,200 volts with step down transformer ratios of 1/10 and 1/20 is in general use, and is recommended.

For long distance, the following average voltages are
recommended 6,000; 11,000; 22,000; 33,000; 44,000; 66,000; 88,000;
and higher, depending on the length of the line and degree of
economy desired.

In alternating circuits the standard frequencies are 25, and 60 cycles. These frequencies are already in extensive use and it is recommended to adhere to them as closely as possible.

In fixing the capacity of a machine, _careful consideration
should be given to the conditions of operation both_ =present=
_and_ =future= in order that the resultant efficiency may be
maximum.

Most machines show the best efficiency at or near full load.
If the load be always constant, as for instance, a pump forcing
water to a given head, it would be a simple matter to specify the
proper size of machine, but in nearly all cases, and especially
in electrical plants, the load varies widely, not only the daily
and hourly fluctuations, but the varying demands depending on
the season of the year and growth of the plant's business. All
of these conditions tend to complicate the matter, so that
intelligent selection of capacity of a machine requires not only
calculation but mature judgment, which is only obtained by long
experience.

In selecting a machine, or in fact any item connected with the plant _its construction should be carefully considered_.

Standard construction should be insisted upon so that in the
event of damage a new part can be obtained with the least possible
delay.

The parts of most machines are _interchangeable_, that is to
say, with the refined methods of machinery a duplicate part
(usually carried in stock) may be obtained at once to replace a
defective or broken part, and made with such precision that little
or no fitting will be required.

The importance of standard construction cannot be better illustrated than in the matter of steam piping, that is, the kind of fittings selected for a given installation.

With the exception of the exhaust line from engine to condenser, where other than standard construction may sometimes be used to reduce the frictional resistance to the steam, the author would adhere to standard construction except in very exceptional cases. Those who have had practical experience in pipe fitting will appreciate the wisdom of this.

For installations in places remote from large supply houses, the more usual forms of standard fittings should be employed, such as ordinary T's, 45° and 90° elbows, etc.

In such locations, where designers specify the less usual forms of standard fittings such as union fittings, offset reducers, etc., or special fittings made to sketch, it simply means, in the first instance that they usually cannot be obtained of the local dealer, making it necessary to order from some large supply house and resulting in vexatious delays.

As a rule, those who specify special fittings have found that their making requires an unreasonable length of time, and the cost to be several times that of the equivalent in standard fittings.

An examination of a few installations will usually show numerous special and odd shape fittings, which are entirely unnecessary.

Moreover, a standard design, in general, is better than a special design, because the former has been tried out, and any imperfection or weakness remedied, and where thousands of castings of a kind are turned out, a better article is usually the result as compared with a special casting.

In the matter of construction, in addition to the items just mentioned, it should be considered with respect to

1. Quality;
2. Range;
3. Accessibility;
4. Proportion;
5. Lubrication;
6. Adjustment.

It is poor policy, excepting in very rare instances, to buy a "cheap" article, as, especially in these days of commercial greed, the best is none too good.

Perhaps next in importance to quality, at least in most cases, is _range_. This may be defined as _scope of operation_, _effectiveness_, or _adaptability_. The importance of range is perhaps most pronounced in the selection of tools, especially for plants remote from repair shops.

For instance, in selecting a pipe cutter, there are two general
classes: wheel cutters, and roller cutters. A wheel cutter has
three wheels and a roller cutter one wheel and two rollers, the
object of the rollers being to keep the wheel perpendicular to
the pipe in starting the cut and to reduce burning. It must be
evident that in operation, a roller cutter requires sufficient
room around the pipe to permit making a complete revolution of
the cutter, whereas, with a wheel cutter, the work may be done
by moving the cutter back and forth through a small arc, as
illustrated in figs. 2,786 and 2,787. Thus a wheel cutter has a
_greater range_ than a roll cutter.

Range relates not only to ability to operate in inaccessible
places but to the various operations that may be performed by one
tool.

PROPERTIES OF STANDARD WROUGHT IRON PIPE

--------------------------+------+-----------------+
| | |
| | |
| | |
| | |
Diameter |Thick-| Circumference. |
| ness.| |
--------+--------+--------+ +--------+--------+
Nominal| Actual | Actual | |External|Internal|
internal|external|internal| | | |
--------+--------+--------+------+--------+--------+
Inches | Inches | Inches |Inches| Inches | Inches |
--------+--------+--------+------+--------+--------+
⅛ | .405 | .27 | .068 | 1.272 | .848 |
¼ | .54 | .364 | .088 | 1.696 | 1.144 |
⅜ | .675 | .494 | .91 | 2.121 | 1.552 |
½ | .84 | .623 | .109 | 2.639 | 1.957 |
¾ | 1.05 | .824 | .113 | 3.299 | 2.589 |
1 | 1.315 | 1.048 | .134 | 4.131 | 3.292 |
1¼ | 1.66 | 1.38 | .14 | 5.215 | 4.335 |
1½ | 1.9 | 1.611 | .145 | 5.969 | 5.061 |
2 | 2.375 | 2.067 | .154 | 7.461 | 6.494 |
2½ | 2.875 | 2.468 | .204 | 9.032 | 7.753 |
3 | 3.5 | 3.067 | .217 | 10.996 | 9.636 |
3½ | 4. | 3.548 | .226 | 12.566 | 11.146 |
4 | 4.5 | 4.026 | .237 | 14.137 | 12.648 |
4½ | 5. | 4.508 | .246 | 15.708 | 14.162 |
5 | 5.563 | 5.045 | .259 | 17.477 | 15.849 |
6 | 6.625 | 6.065 | .28 | 20.813 | 19.054 |
7 | 7.625 | 7.023 | .301 | 23.955 | 22.063 |
8 | 8.625 | 7.982 | .322 | 27.096 | 25.076 |
9 | 9.625 | 8.937 | .344 | 30.238 | 28.076 |
10 | 10.75 | 10.019 | .366 | 33.772 | 31.477 |
11 | 12. | 11.25 | .375 | 37.699 | 35.343 |
12 | 12.75 | 12. | .375 | 40.055 | 37.7 |
--------+--------+--------+------+--------+--------+
------+-------------------------+---------------+--------+-------+------
| | | | |
| | | | |
| | | Length | |
| |Length of pipe |of pipe |Nominal|
Diam.| Transverse areas. | per square |contain-|weight |Number
| | foot of |ing one | per | of
------+--------+--------+-------+-------+-------+ cubic | foot. |thread
Nom. |External|Internal| Metal |Ext'nal|Int'nal| foot. | | per
intern| | | |surface|surface| | | inch
------+--------+--------+-------+-------+-------+--------+-------+ of
Inches|Sq. ins.|Sq. ins.|Sq.ins.| Feet | Feet | Feet |Pounds |screw
------+--------+--------+-------+-------+-------+--------+-------+-----
⅛ | .129 | .0573| .0717| 9.44 |14.15 |2513. | .241 | 27
¼ | .229 | .1041| .1249| 7.075 |10.49 |1383.3 | .42 | 18
⅜ | .358 | .1917| .1663| 5.657 | 7.73 | 751.2 | .559 | 18
½ | .554 | .3048| .2492| 4.547 | 6.13 | 472.4 | .837 | 14
¾ | .866 | .5333| .3327| 3.637 | 4.635 | 270. | 1.115 | 14
1 | 1.358 | .8626| .4954| 2.904 | 3.645 | 166.9 | 1.668 | 11½
1¼ | 2.164 | 1.496 | .668 | 2.301 | 2.768 | 96.25 | 2.244 | 11½
1½ | 2.835 | 2.038 | .797 | 2.01 | 2.371 | 70.66 | 2.678 | 11½
2 | 4.43 | 3.356 | 1.074 | 1.608 | 1.848 | 42.91 | 3.609 | 11½
2½ | 6.492 | 4.784 | 1.708 | 1.328 | 1.547 | 30.1 | 5.739 | 8
3 | 9.621 | 7.388 | 2.243 | 1.091 | 1.245 | 19.5 | 7.536 | 8
3½ | 12.566 | 9.887 | 2.679 | .955 | 1.077 | 14.57 | 9.001 | 8
4 | 15.904 | 12.73 | 3.174 | .849 | .949 | 11.31 |10.665 | 8
4½ | 19.635 | 15.961 | 3.674 | .764 | .848 | 9.02 |12.34 | 8
5 | 24.306 | 19.99 | 4.316 | .687 | .757 | 7.2 |14.502 | 8
6 | 34.472 | 28.888 | 5.584 | .577 | .63 | 4.98 |18.762 | 8
7 | 45.664 | 38.738 | 6.926 | .501 | .544 | 3.72 |23.271 | 8
8 | 58.426 | 50.04 | 8.386 | .443 | .478 | 2.88 |28.177 | 8
9 | 72.76 | 62.73 |10.03 | .397 | .427 | 2.29 |33.701 | 8
10 | 90.763 | 78.839 |11.924 | .355 | .382 | 1.82 |40.065 | 8
11 |113.098 | 99.402 |13.696 | .318 | .339 | 1.450|45.95 | 8
12 |127.677 |113.098 |14.579 | .299 | .319 | 1.27 |48.985 | 8
------+--------+--------+-------+-------+-------+--------+-------+----

Open construction should be employed, wherever possible, so that all parts of a machine that require attention, or that may become deranged in operation, may be accessible for adjustment or repair.

The design should be such that there is ample strength, and the
bearings for moving parts should be of liberal proportions to
avoid heating with minimum attention.

A comparison of the proportions used by different manufacturers
for a machine of given size might profitably be made before a
selection is made.

The matter of lubrication is important.

Fast running machines, such as generators and motors, should be
provided with ring oilers and oil reservoirs of ample capacity, as
shown in figs. 2,788 to 2,794.

All bearings subject to appreciable wear should be made adjustable so that lost motion may be taken up from time to time and thus keep the vibration and noise of operation within proper limits.

=Selection of Generators.=--This is governed by the class of work to be done and by certain local conditions which are liable to vary considerably for different stations.

These variable factors determine whether the generators must be of the direct or alternating current type, whether they must be wound to develop a high or a low voltage, and whether their outputs in amperes must be large or small. Sufficient information has already been given to cover these various cases; there are, however, certain general rules that may advantageously be observed in the selection of generators designed to fill any of the aforementioned conditions, and it is well to possess certain facts regarding their construction.

=Ques. Name an important point to be considered in selecting a generator.=

Ans. Its efficiency.

=Ques. What are the important points with respect to efficiency?=

Ans. A generator possessing a high efficiency at the average load is more desirable than a generator showing a high efficiency at full load.

=Ques. Why?=

Ans. The reason is that in station practice the full load limit is seldom reached, the usual load carried by a generator ordinarily lying between the one-half and three-quarter load points.

=Ques. How do the efficiencies of large and small generators compare?=

Ans. There is little difference.

=Ques. How are the sizes and number of generator determined?=

Ans. The sizes and number of generator to be installed should be such as to permit the engines operating them being worked at nearly full load, because the efficiencies of the latter machines decrease rapidly when carrying less than this amount.

=Ques. What is understood by regulation?=

Ans. The accuracy and reliability with which the pressure or current developed in a machine may be controlled.

It is generally possible if purchasing of a reputable concern,
to obtain access to record sheets on which may be found results
of tests conducted on the generator in question, and as these are
really the only means of ascertaining the values of efficiency and
regulation, the purchaser has a right to inspect them. If, for
some reason or other, he has not been afforded this privilege, he
should order the machine installed in the station on approval, and
test its efficiency and regulation before making the purchase.

=Installation.=--The installation of machines and apparatus in an electrical station is a task which increases in difficulty with the size of the plant. When the parts are small and comparatively light they may readily be placed in position, either by hand, by erecting temporary supports which may be moved from place to place as desired, or by rolling the parts along on the floor upon pieces of iron pipe. If, however, the parts be large and heavy, a traveling crane such as shown in fig. 2,797, becomes necessary.

=Ques. What precaution should be taken in moving the parts of machines?=

Ans. Care should be taken not to injure the bearings and shafts, the joints in magnetic circuits such as those between frame and pole pieces, and the windings on the field and armature.

The insulations of the windings are perhaps the most vital parts
of a generator, and the most readily injured. The prick of a pin
or tack, a bruise, or a bending of the wires by resting their
weight upon them or by their coming in contact with some hard
substance, will often render a field coil or an armature useless.

Owing to its costly construction, it is advisable when
transporting armatures by means of cranes to use a wooden
spreader, as shown in fig. 2,798 to prevent the supporting rope
bruising the winding.

=Ques. If an armature cannot be placed at once in its final position what should be done?=

Ans. It may be laid temporarily upon the floor, if a sheet of cardboard or cloth be placed underneath the armature as a protection for the windings; in case the armature is not to be used for some time, it is better practice to place it in a horizontal position on two wooden supports near the shaft ends.

=Ques. What kind of base should be used with a belt driven generator or motor?=

Ans. The base should be provided with V ways and adjusting screws for moving the machine horizontally to take up slack in the belt, as shown in fig. 2,799.

Owing to the normal tension on the belt, there is a moment
exerted equal in amount to the distance from the center of gravity
of the machine to the center of the belt, multiplied by the
effective pull on the belt. This force tends to turn the machine
about its center of gravity. By placing the screws as shown, any
turning moment, as just mentioned, is prevented.

=Ques. How should a machine be assembled?=

Ans. The assembling should progress by the aid of a blue print, or by the information obtained from a photograph of the complete machine as it appears when ready for service. Each part should be perfectly clean when placed in position, especially those parts between which there is friction when the machine is in operation, or across which pass lines of magnetic force; in both cases the surfaces in contact must be true and slightly oiled before placing in position.

Contact surfaces forming part of electrical circuits must also
be clean and tightly screwed together. An important point to bear
in mind when assembling a machine is, to so place the parts that
it will not be necessary to remove any one of them in order to get
some other part in its proper position. By remembering this simple
rule much time will be saved, and in the majority of instances the
parts will finally be better fitted together than if the task has
to be repeated a number of times.

When there are two or more parts of the machine similarly
shaped, it is often difficult to properly locate them, but in such
cases notice should be taken of the factory marks usually stamped
upon such pieces and their proper places determined from the
instructions sent with the machine.

=Ques. What should be noted with respect to speed of generator?=

Ans. Each generator is designed to be run at a certain speed in order to develop the voltage at which the machine is rated. The speed, in revolutions per minute, the pressure in volts, and the capacity or output in watts (volts × amperes) or in kilowatts (thousands of watts) are generally stamped on a nameplate screwed to the machine.

This requirement frequently requires calculations to be made by
the erectors to determine the proper size pulleys to employ to
obtain the desired speed.

=Example.=--What diameter of engine pulley is required to run
a dynamo at a speed of 1,450 revolutions per minute the dynamo
pulley being 10 inches in diameter and the speed of engine, 275
revolutions per minute?

The diameter of pulley required on engine is 10 × (1,450 ÷ 275) = 53 inches, nearly.

=Rule.=--To find the diameter of the driving pulley, _multiply
the speed of the driven pulley by its diameter, divide the product
by the speed of the driver and the answer will be the size of the
driver required_.

_Example._--If the speed of an engine be 325 revolutions per
minute, diameter of engine pulley 42 inches, and the speed of
the dynamo 1,400 revolutions per minute, how large a pulley is
required on dynamo?

The size of the dynamo pulley is

42 × (325 ÷ 1,400) = 9¾ inches.

=Rule.=--To find the size of dynamo pulley, _multiply the speed
of engine by the diameter of engine wheel and divide the product
by the speed of the dynamo_.

_Example._--If a steam engine, running 300 revolutions per
minute, have a belt wheel 48 inches in diameter, and be belted
to a dynamo having a pulley 12 inches in diameter, how many
revolutions per minute will the dynamo make?

The speed of dynamo will be 300 × (48 ÷ 12) = 1,200 rev. per min.

=Rule.=--When the speed of the driving pulley and its diameter
are known, and the diameter of the driven pulley is known, the
speed of the driven pulley is found by _multiplying the speed of
the driver by its diameter in inches and dividing the product by
the diameter of the driven pulley_.

=Example.=--What will be the required speed of an engine
having a belt wheel 46 inches in diameter to run a dynamo 1,500
revolutions per minute, the dynamo pulley being 11 inches in
diameter?

The speed of the engine is 1,500 × (11 ÷ 46) = 359 rev. per min.
nearly.

=Rule.=--To find the speed of engine when diameter of both
pulleys, and speed of dynamo are given, _multiply the dynamo speed
by the diameter of its pulley and divide by the diameter of engine
pulley_.

=Ques. How are the diameters and speeds of gear wheels figured?=

Ans. The same as belted wheels, using either the pitch circle diameters or number of teeth in each gear wheel.

=Ques. What should be noted with respect to generator pulleys?=

Ans. A pulley of certain size is usually supplied with each generator by its manufacturer, and it is not generally advisable to depart much from the dimensions of this pulley. Accordingly, the solution of the pulley problem usually consists in finding the necessary diameter of the driving pulley relative to that of the pulley on the generator in order to furnish the required speed.

=Ques. What is the chief objection to belt drive?=

Ans. The large amount of floor space required.

=Ques. How may the amount of space that would ordinarily be required for belt drive, be reduced?=

Ans. By driving machines in tandem as in fig. 2,810, or by the double pulley drive as in fig. 2,811.

=Ques. What is the objection to the tandem method?=

Ans. The most economical distance between centers cannot be employed for all machines.

=Ques. What is the objectionable tendency in resorting to floor economy methods with belt transmission?=

Ans. The tendency to place the machines too closely together. This is poor economy as it makes the cleaning of the machines a difficult and dangerous task; it is therefore advisable to allow sufficient room for this purpose regardless of the method of belting employed.

=Ques. What is the approved location for an alternator exciter?=

Ans. To economize floor space the exciter may be placed between the alternator and engine at S in fig. 2,811.

=Belts.=--In the selection of a belt, the quality of the leather should be first under consideration. The leather must be firm, yet pliable, free from wrinkles on the grain or hair side, and of an even thickness throughout.

If the belt be well selected and properly handled, it should do service for twenty years, and even then if the worn part be cut off, the remaining portion may be remade and used again as a narrower and shorter belt.

Besides leather belts, there are those made of rubber which
withstand moisture much better than leather belts, and which also
possess an excellent grip on the pulley; they are, however, more
costly and much less durable under normal conditions.

In addition to leather and rubber belts, there are belts
composed of cotton, of a combination of cotton and leather, and
of rope. The leather belt, however, is the standard and is to be
recommended.

Equally important with the quality of a belt is its size in order to transmit the necessary power.

The average strain under which leather will break has been found
by many experiments to be 3,200 pounds per square inch of cross
section. A good quality of leather will sustain a somewhat greater
strain. In use on the pulleys, belts should not be subjected to a
greater strain than one eleventh their tensile strength, or about
290 pounds to the square inch or cross section. This will be about
55 pounds average strain for every inch in width of single belt
three-sixteenths inch thick. The strain allowed for all widths
of belting--single, light double, and heavy double--is in direct
proportion to the thickness of the belt.

=Ques. How much horse power will a belt transmit?=

Ans. The capacity of a belt depends on, its width, speed, and thickness. _A single belt one inch wide and travelling 1,000 feet per minute will transmit one horse power; a double belt under the same conditions, will transmit two horse power._

This corresponds to a working pull of 33 and 66 lbs. per inch of
width respectively.

=Example.=--What width double belt will be required to transmit
50 horse power travelling at a speed of 3,000 feet per minute?

The horse power transmitted by each inch width of double belt
travelling at the stated speed is

3,000
1 × ----- × 2 = 6,
1,000

hence the width of belt required to transmit 50 horse power is

50 ÷ 6 = 8.33, say 8 inches.

=Ques. At what velocity should a belt be run?=

Ans. At from 3,000 to 5,000 feet per minute.

=Ques. How may the greatest amount of power transmitting capacity be obtained from belts?=

Ans. By covering the pulleys with leather.

=Ques. How should belts be run?=

Ans. With the tight side underneath as in fig. 2,814.

=Ques. What is a good indication of the capacity of a belt in operation?=

Ans. Its appearance after a few days' run.

If the side of the belt coming in contact with the pulley assume
a mottled appearance, it is an indication that the capacity of
the belt is considerably in excess of the power which it is
transmitting, inasmuch as the spotted portions of the belt do not
touch the pulley; and in consequence of this there is liable to be
more or less slipping.

Small quantities of a mixture of tallow and fish oil which
have previously been melted together in the proportion of two of
the former to one of the latter, will, if applied to the belt
at frequent intervals, do much toward softening it, and thus
by permitting its entire surface to come in contact with the
pulley, prevent any tendency toward slipping. The best results
are obtained when the smooth side of the belt is used next to the
pulley, since tests conducted in the past prove that more power is
thus transmitted, and that the belt lasts longer when used in this
way.

=Ques. What is the comparison between the so called endless belts and laced belts?=

Ans. With an endless belt there is no uneven or noisy action as with laced belts, when the laced joint passes over the pulleys, and the former is free from the liability of breakage at the joint.

=Ques. How should a belt be placed on the pulleys?=

Ans. The belt should first be placed on the pulley at rest, and then run on the other pulley while the latter is in motion.

The best results are obtained, and the strain on the belt is
less, when the speed at which the moving pulley revolves is
comparatively low. With heavy belts, particular care should be
taken to prevent any portion of the clothing being caught either
by the moving belt or pulleys, as many serious accidents have
resulted in the past from carelessness in regard to this important
detail. The person handling the belt should, therefore, be sure of
a firm footing, and when it is impossible to secure this, it is
advisable to stop the engine and fit the belt around the engine
pulley as well as possible by the aid of a rope looped around the
belt.

=Ques. Under what conditions does a belt drive give the best results?=

Ans. When the two pulleys are at the same level.

If the belt must occupy an inclined position it should not form
a greater angle than 45 degrees with the horizontal.

=Ques. What is a characteristic feature in the operation of belts, and why?=

Ans. Belts in motion will always run to the highest side of a pulley; this is due partially to the greater speed in feet per minute developed at that point owing to the greater circumference of the pulley, and also to the effects of centrifugal force.

If, therefore, the highest sides of both pulleys be in line with
each other, and the shafts of the respective pulleys be parallel
to each other, there will be no tendency for the belt to leave
the pulleys when once in its proper position. In order that these
conditions be maintained, the belt should be no more than tight
enough to prevent slipping, and the distance between the centers
of the pulleys should be approximately 3.5 times the diameter of
the larger one.

=Ques. What minor appurtenances should be provided in a station?=

Ans. Apparatus should be installed as a prevention against accidents, such as fire, and protection of attendants from danger.

In every electrical station there should be a pump, pipes
and hose; the pump may be either directly connected to a small
electric motor or belted to a countershaft, while the pipes
and hose should be so placed that no water can accidentally
reach the generators and electrical circuits. A number of fire
bucket filled with water should be placed on brackets around the
station, and with these there should be an equal number of bucket
containing dry sand, the water being used for extinguishing fire
occurring at a distance from the machines and conductors, and the
sand for extinguishing fire in current carrying circuits where
water would cause more harm than benefit. To prevent the sand
being blown about the station, each sand bucket, when not in use,
should be provided with a cover.

Neat cans and boxes should be mounted in convenient places for
greasy rags, waste, nuts, screws, etc., which are used continually
and which therefore cannot be kept in the storeroom.

While it is important to guard against fire in the station,
it is equally necessary to provide for personal safety. All
passages and dark pits should therefore be thoroughly lighted
both day and night, and obstacles of any nature that are not
absolutely necessary in the operation of the station, should be
removed. Moving belts, and especially those passing through the
floor, should be enclosed in iron railings. If high voltages be
generated, it is well to place a railing about the switchboard to
prevent accidental contact with current carrying circuits, and in
such cases it is also advisable to construct an insulated platform
on the floor in front of the switchboard.

=Switchboards.=--The plan of switchboard wiring for alternating current work depends upon the system in use and this latter may be either of the single phase, two phase, three phase, or monocyclic types. The general principles in all these cases, however, are practically identical.

Fig. 2,820 shows the switchboard wiring for a single phase
alternator. As an aid in reading the diagram, the conductors
carrying alternating current are represented by solid lines, and
those carrying direct current, by dotted lines.

The exciter shown at the right is a shunt wound machine. By
means of the exciter rheostat, the voltage for exciting the field
winding of the alternator is varied; this, in turn, varies the
voltage developed in the alternator since the main leads of the
exciter are connected through a double pole switch G to the field
winding of the alternator.

A rheostat is also introduced in the alternator field winding
circuit to adjust the alternator pressure. It may seem unnecessary
to employ a rheostat in each of two separate field circuits to
regulate the voltage of the alternator, but these rheostats are
not both used to produce the same result. When a considerable
variation of pressure is required, the exciter rheostat is
manipulated, whereas for a fine adjustment of voltage the
alternator rheostat is preferably employed.

Sometimes a direct current ammeter is introduced in the
alternator's field circuit to aid in the adjustment.

The main circuit of alternator after being protected on both
sides by fuses, runs to the double pole switch K. These fuses
serve as a protection to the alternator in case of a short circuit
at the main switch. It will be noticed the fuses are of the single
pole type and are mounted a considerable distance apart; this is
to prevent any liability of a short circuit between them in case
of action. Enclosed fuses are now used entirely for such work,
since in these there is no danger of heated metal being thrown
about and causing damage when the fuse wire is melted. Enclosed
fuses are also more readily and quickly replaced than open fuses,
the containing tube of each being easy to adjust in circuit, and
when the fuse wire within is once melted the tube is discarded for
a new one.

The main circuit after passing through the main switch is
further protected on both sides by circuit breakers. Leaving these
protective devices, the left hand side of the circuit includes
the alternating current ammeter, and then connects with one of
the bus bars. The right hand side of the circuit runs from the
circuit breaker to the other bus bar. As many feeder circuits
may be connected to the bus bars and supplied with current by
the alternator as the capacity of this machine will permit. If,
however, there be more than one feeder circuit, each must be wired
through a double pole switch.

In alternating current work the pressures dealt with are much
greater than those in direct current installations, so that
proportionate care must be taken in the wiring to remove all
possibility of grounds.

To locate such troubles, however, should they occur, a ground
detector is provided. For this class of work the ground detector
must be an instrument especially designed for high pressure
circuits. Two of its terminals should be connected to the line
wires and the third, to ground; in case of a leak on the line, a
current will then flow through the detector and by the position of
the pointer the location and seriousness of the leak may be judged.

A step down transformer is also rendered necessary for the
voltmeter and the pilot lamps, owing to the high voltage in use.
The primary winding of the transformer is connected across the
main circuit of the alternator. This connection should never be
made so that it will be cut out of circuit when the main switch is
open, for it is always advisable to consult the voltmeter before
throwing on the load by closing this switch.

=Ques. How does the switchboard wiring for a two phase system differ from the single phase arrangement shown in fig. 2,820?=

Ans. It is practically the same, except for the introduction of an extra ammeter and a compensator in each of the outside wires, and in the use of a four pole switch in place of the two pole main switch.

The ammeters, of course, are for measuring the alternating
currents in each of the two phases or legs of the system, and the
compensators are two transformers with their primary coils in
series with the outside wires and their secondary coils in series
with each other across the outside wires. The transformers thus
connected are known as compensators or pressure regulators, and
as such compensate for the drop in pressure on either side of the
system.

=Ques. How is the four pole main switch wired?=

Ans. Its two central terminals which connect directly with the line wires, are joined together by a conductor, and from this point one wire is led off. This wire, together with the two outside wires, form the feeders of the system.

=Ques. How many voltmeters are required for the two phase system?=

Ans. One voltmeter is sufficient on the board if a proper switching device be employed to shift its connections across either of the two circuits; otherwise, two voltmeters will be necessary, one bridged across each of these respective circuits.

The same reasoning holds true in regard to ground detectors,
so that one or two of these will be required, depending upon the
aforementioned conditions.

=Ques. What are the essential points of difference between the single phase switchboard wiring as shown in fig. 2,820, and that required for a three wire three phase system?=

Ans. The three phase system requires the use of a three pole switch in place of the two pole switch; the insertion of an ammeter, a circuit breaker, and a compensator in each of the three wires of the system; the presence of two ground detectors instead of one, and the addition of a voltmeter switch if but one voltmeter be provided, or else the installation of two voltmeters, connected the one between the middle wire and outer right hand wire, and the other between the middle wire and outer left hand wire.

=Ques. Mention a few points relating to lightning arresters.=

Ans. In most cases where direct current is used they are mounted on the walls of the station near the place at which the line wires enter. If they be mounted outside the station at this point, special precautions should be taken to keep them free from moisture by enclosing them in iron cases, but no matter where they are located it is necessary that they be dry in order to work properly.

If possible, one place should be set aside for them and a marble
or slate panel provided on which they may be mounted.

Wooden supports are undesirable for lightning arresters on
account of the fire risk incurred; this, however, may be reduced
to a minimum by employing skeleton boards and using sheets of
asbestos between the arresters and the wood.

In parts of the country where lightning is of common occurrence
and where overhead circuits are installed which carry high
pressures, heavy currents, and extend over considerable territory,
it is advisable to have the station well equipped with lightning
arresters of the most improved types.

In each side of the main circuit, between the lightning arrester
connections and the switchboard apparatus there should be
connected a choke coil or else each of the main conductors at this
point should be tightly coiled up part of its length to answer the
same purpose.

A quick and effective way of coiling up a wire consists in
wrapping around a cylindrical piece of iron or wood that part
of the conductor in which it is desired to have the coils, the
desired number of times, and then withdrawing the cylindrical
piece. The coils, each of which may contain 50 or 200 turns,
thus inserted in the main circuit introduce a high resistance or
reluctance to a lightning current, and thus prevent it passing
to the generator; there will, however, be an easy path to earth
afforded it through the lightning arrester, and so no damage will
be done. Coils of the nature just mentioned may advantageously be
introduced between the generator and switchboard to take up the
reactive current developed upon the opening of the circuit, and in
the case of suspended conductors, the coils may be used to take up
the slack by the spring-like effect produced by them.

The safety of the operator should be especially considered in
the design of high pressure alternating current switchboards.

Such protection may be secured by screening all the exposed
terminals, or preferably by mounting all the switch mechanism on
the back of the board with simply the switch handle projecting
through to the front; by pushing or pulling the switch handle, the
connections can thus be shifted either to one side of the system
or to the other.

=Ques. Upon what does the work of assembling a switchboard depend?=

Ans. It depends almost entirely upon the size of the plant, varying from the simple task of mounting a single panel in the case of an isolated plant, to the more difficult problem of supporting a large number of panels in a central station.

=Ques. When the material chosen for a switchboard must be shipped a considerable distance, what form of board should be used?=

Ans. The board units or "slabs" should be of small dimensions, to avoid the liability of breakage and expense of renewal when a unit becomes cracked or machine injured.

Ordinarily, switchboards vary from five to eight feet in
height and the widths of the panels vary from five to six feet.
In some boards the seams between the slabs run vertically, and
in others horizontally. In order to render the assembling of
the switchboard as simple as possible, and its appearance when
finished the most artistic, these seams should run horizontally
rather than vertically. The edges of each of the slabs should also
be chamfered so that there will be less danger of their breaking
out when being mounted on the framework.

=Ques. In assembling a switchboard, how should the lower slabs be placed, and why?=

Ans. They should be suspended a little distance from the floor to prevent contact with any oil, dirt, water or rubbish that might be on the floor.

=Ques. How are the slabs or panels supported?=

Ans. They are carried on an iron or wooden framework with braces to give stability.

The braces should be securely fastened at one end to the wall of
the station, and at the other end to the framework of the board,
as shown in fig. 2,836.

To fasten the switchboard end of the brace directly to the
slate, marble or other material composing the board is poor
practice and should never be attempted.

If the station be constructed of iron, these switchboard braces
must be such that they will thoroughly insulate the board and its
contents from the adjoining wall.

=Ques. What is the usual equipment of a switchboard?=

Ans. It comprises switching devices, current or pressure limiting devices, indicating devices, and fuses for protecting the apparatus and circuits.

On some switchboards are also mounted small transformers for
raising or lowering the voltages, and lightning arresters as a
protection from lightning. In addition to the apparatus previously
mentioned nearly all switchboards carry at or near their top two
or more incandescent lamps provided with shades or reflectors, for
lighting the board.

=Ques. What should be done before wiring a switchboard?=

Ans. The electrical connections between the various apparatus mounted on the face or front of the board, are made on the back of the board. It is necessary that these connections be properly made else considerable electrical power will be wasted at this point. The wiring on the back of the board should therefore be planned out on paper before commencing the work.

In laying out the plan of wiring care must be taken to allow
sufficient contact surface at each connection; there should be not
less than one square inch of contact surface allowed for each 160
amperes of current transmitted.

For the bus bars, which, by the way are always of copper, one
square inch per 1,000 amperes is the usual allowance; this is
equal to 1,000 circular mils of cross sectional area per ampere.

Every effort should be made to give the bus bars the greatest
amount of radiation consistent with other conditions, in order
that their resistances may not become excessive owing to the heat
developed by the large currents they are forced to carry. Suppose,
for instance, the number of amperes to be generated is such as
to require bus bars having each a cross sectional area of one
square inch. If the end dimensions of these bars were each 1 inch
by 1 inch, there would be less radiating surface than if their
dimensions were each 2 inches by ½ inch.

=Operation of Alternators.=--The operation of an alternator when run singly differs but little from that for a dynamo.

As to the preliminaries, the exciter must first be started.
This is done in the same way as for any shunt dynamo. At first
only a small current should be sent through the field winding of
the alternator; then, if the exciter operates satisfactorily and
the field magnetism of the operator show up well, the load may
gradually be thrown on until the normal current is carried, the
same method of procedure being followed as in the similar case of
a dynamo.

On loading an alternator, a noticeable drop in voltage occurs across its terminals. This drop in voltage is caused in part by the demagnetization of the field magnets due to the armature current, and so depends in a measure upon the position and form of the pole pieces as well as upon those of the teeth in the armature core. The resistance of the armature winding also causes a drop in voltage under an increase of load.

Another cause which may be mentioned is the inductance of the
armature winding, which is in turn due to the positions of the
armature coils with respect to each other and also with respect to
the field magnets.

=Alternators in Parallel.=--When the load on a station increases beyond that which can conveniently be carried by one alternator, it becomes necessary to connect other alternators in parallel with it. To properly switch in a new machine in parallel with one already in operation and carrying load, requires a complete knowledge of the situation on the part of the attendant, and also some experience.

The connections for operating alternators in parallel are
shown in fig. 2,843. In the illustration the alternator A is in
operation and is supplying current to the bus bars. The alternator
B is at rest. The main pole switch B' by means of which this
machine can be connected into circuit is therefore open.

Now, if the load increase to such extent as to require the
service of the second alternator B, it must be switched in
parallel with A. In order that both machines may operate properly
in parallel, three conditions must be satisfied before they are
connected together, or else the one alternator will be short
circuited through the other, and serious results will undoubtedly
follow.

Accordingly before closing main switch B, it is necessary that

1. The frequencies of both machines be the same;
2. The machines must be in synchronism;
3. The voltages must be the same.

=Ques. How are the frequencies made the same?=

Ans. By speeding up the alternator to be cut in, or change the speed of both until frequency of both machines is the same.

=Ques. How are the alternators synchronized or brought in phase?=

Ans. The synchronism of the alternators is determined by employing some form of synchronizer, as by the single lamp method of fig. 2,843, or the two lamp method of fig. 2,845.

=Ques. In synchronizing by the one lamp method, when should the incoming machine be thrown in?=

Ans. It is advisable to close the switch when the machines are approaching synchronism rather than when they are receding from it, that is to say, the instant the lamp becomes dark.

=Ques. What are the objections to the one lamp method?=

Ans. The filament of the lamp may break, and cause darkness, or the lamp may be dark with considerable voltage as it takes over 20 volts to cause a 100 volt lamp to glow.

=Ques. What capacity of single lamp must be used?=

Ans. It must be good for twice the voltage of either machine.

=Ques. What modification of the synchronizing methods shown in the accompanying illustrations is necessary when high pressure alternators are used?=

Ans. Step down transformers must be used between the alternators and the lamps to obtain the proper working voltages for the lamps.

=Ques. How is the voltage of an incoming machine adjusted so that it will be the same as the one already in operation?=

Ans. By varying the field excitation with a rheostat in the alternator field circuit.

=Ques. How may two or more alternators be started simultaneously?=

Ans. After bringing each of them up to its proper speed so as to obtain equal frequencies, the main switches may be closed, thereby joining their armature circuits in parallel. As yet, however, their respective field windings have not been supplied with current, so that no harm can result in doing this. The exciters of these machines after being joined in parallel, should then be made to send direct current simultaneously through the field windings of the alternators, and from this stage on the directions previously given may be followed in detail.

=Ques. What are the conditions when two or more alternators are directly connected together?=

Ans. If rigidly connected together, or directly connected to the same engine, they must necessarily run in the same manner at all times.

When machines connected in this way are once properly adjusted
so that they are in phase with each other, their operation in
parallel is even a simpler task than when they are all started
together but are not directly connected.

=Ques. When an alternator is driven by a gas engine, what provision is sometimes made to insure successful operation in parallel?=

Ans. An amortisseur winding is provided to counteract the tendency to "hunting."

=Ques. What is the action of the amortisseur winding?=

Ans. Any sudden change in the speed of the field, generates a current in the amortisseur winding which resists the change of velocity that caused the current.

The appearance of an amortisseur winding is shown in the cut
below (fig. 2,850) illustrating the field of a synchronous
condenser equipped with amortisseur winding.

=Ques. How are three phase alternators synchronized?=

Ans. In a manner similar to the single phase method.

Thus the synchronizing lamps may be arranged as in fig. 2,581,
which is simply an extension of the single phase method.

=Ques. Are three lamps necessary?=

Ans. Only to insure that the connections are properly made, after which one lamp is all that is required.

=Ques. How is it known that the connections of fig. 2,851 are correct?=

Ans. If, in operation, the three lamps become bright or dark _simultaneously_, the connections are correct; if this action takes place _successively_, the connections are wrong.

If wrong, transpose the leads of one machine until simultaneous
action of the lamps is secured.

=Ques. What is the disadvantage of the lamp method of synchronizing?=

Ans. Lack of sensitiveness.

=Ques. Which is the accepted lamp method, dark or brilliant?=

Ans. In the United States it is usual to make the connections for a dark lamp at synchronism, while in England the opposite practice obtains.

With the dark lamp method, the breaking of a filament might
cause the machines to be connected with a great phase difference,
whereas, with the brilliant lamp it is difficult to determine the
point of maximum brilliancy. This latter method, therefore may be
called the safer.

=Ques. What may be used in place of lamps for synchronizing?=

Ans. Some form of synchroscopes, or synchronizers.

=Ques. How does the Lincoln synchronizer work?=

Ans. The construction is such that a hand moves around a dial so that the angle between the hand and the vertical is always the phase angle between the two sources of electric pressure to which the synchronizer is connected.

If the incoming alternator be running too slow, the hand
deflects in one direction, if too fast, in the other direction.
When the hand shows no deflection, that is, when it stands
vertical, the machines are in phase. A complete revolution of the
hand indicates a gain or loss of one cycle in the frequency of the
incoming machine, as referred to the bus bars.

=Cutting Out Alternator.=--When it is desired to cut out of circuit an alternator running in parallel with others, the method of procedure is as follows:

1. Reduce driving power until the load has been transferred
to the other alternators, adjusting field rheostat to obtain
minimum current;
2. Open main switch;
3. Open field switch.

=Ques. What precaution should be taken?=

Ans. _Never_ open field switch before main switch.

=Ques. What is the ordinary method of cutting out an alternator?=

Ans. The main switch is usually opened without any preliminaries.

=Ques. What is the objection to this procedure?=

Ans. It suddenly throws all the load on the other alternators, and causes "hunting."

=Ques. What forms of drive are especially desirable for running alternators in parallel, and why?=

Ans. Water turbine or steam turbine because of the uniform torque, thus giving uniform motion of rotation.

With reciprocating engines, the crank effect is very variable
during the revolution, resulting in pulsations driving the
alternator too fast or too slow, and causing cross current between
the alternators.

=Ques. Is a sluggish, or a too sensitive governor preferable on an engine driving alternators in parallel?=

Ans. A sluggish governor.

=Alternators in Series.=--Alternators are seldom if ever connected in series, for the reason that the synchronizing tendency peculiar to these machines causes them to oppose each other and fall out of phase when they are joined together in this way. If, however, they be directly connected to each other, or to an engine, so that they necessarily keep in phase at all times, and thus add their respective voltages instead of counteracting them, series operation is possible.