The Montgomery advertiser., 1901-10-03
ELECTRICAL ENGINEERING
By Arthur E. watson. A. M.

POWER TRANHMlSSlON GENERA used either as a generator or motor.has been explained in previous papers Dur ing the greater part of it's construction % na ssocgy ssy :o s svifn faans nss ever, the winding and testing may be equally appropriate for either adoption; only the final arrangements or connect, the distinction between generator and motor. The former would usually have provision for inserting regulating rneo- stat in the field circuit. ana the ,n latles ass armature circuit. A further difference would usually exist in use of a compound field winding for the generator. ana plain shunt or series held winding TOT the mo
 Admitting these considerations only, the generator and motor might be of the with % simcst % Identical apparatus at each end of the line. have been instaitea. | Usually. however. the power Is not to pe delivered at one point put o,ors ostriPsaee Henee the evolution has been. in most cases. to retain ordinary sizes of motors but con tinually to make larger gno fsnepsathorss hss ,.sn n constructed, in 1898 one of 2ooo H.. P, was operating the intramural railroad at | the worlds fair. A score or more or ioen- tical size are now In regular sevfce .tt,, tor isrSer size are being installed and 5.ooo H, F. er-drfven generators have peer running for several years at Niagars,; g,.,
 | in 1881 that the commercial possibility or electric power transmission or distribu- tion was demonstrated The invention or electric lighting had resStea in sns some nf these, used as motors, were regu- | iarly driving considerable machinery. Ed. ison's 'Jumbo type Of diIec'-eoddpissaS, n1se sod sa, amperes was exhibited to the wonder and | admiration of artisans and scientists. | Count Du Moncei. only three years before nsq not wrise forever % be ' on guard against the l pompous announcements Of certain con l structors and of certain periodicals, wno l affirm that electromoters can pc esssp.:s iished having the force of several horsss. | He was a daily visitor at the exhinition' l observing motors of greater power m sue. l cessful use; especially was ne interesteu a time. sometimes stroking its field coll as a man might caress favorite horse. | In the same year Marcel Deorez attempt ed transmissiCn of pow;ssr ;ss,,,cai taI rsm- ala- me series machines were installed; about tor r. and S about IF H. P. was realized Ut the actual conditions are not on record. but it is probable that the resistance or | line wires was considerable. and tnat l however, the defective Insulation soon caused the ruin of the apparatus. The writer remembers having had hand m 1890 in the design of somewhat similar | apparatus for a pioneer installation for carrying power from a waterfall thirteen miles distant to Hartford. Conn The ma- chimes were to be alike. of 200 K. w; ca pacity. four-pole belted type Of railway generators just then introduced-but so- Ties wound for 3.000 volts; commutator had 900 segments. Such transmission might work well under Ter unifotm tha Gona,- contn- would result in considerable change ot speed. More serious is the problem or starting and stopping the motor: sns m need to be gradually reduced by meana of a suitable rheostat A sudden rupture of the circuit, either intentional or acci- dental, would be reason of the high selI-
 induction of the system puncture the in- sulation. .
 Just at this time the utility of alternat.
 ing currents for operating motors was recognized, and now for all distances Igreater than 8 few miles they alone are
 employed While alternating-current gen- orators in themselves are a little cheap CT to construct than those of the same output for direct currents. their real ad-
 vantage consists in the ability to furnish high potentials, whereby small line wires dIstances' In some cases the high poten- tials are produced directly in the arma- lures of the generators, and the motors
 adapted to receive nsarly srsnat0lera as mGen6 la would be used at the receiving end, to allow a lower and safer potential at the motors or there might be double sets of or sO0 volts. the 'step-up" transformers raising it to 1l,000, the "step-down" trans formers at the other end of the line re.
 ceiving 10000 and delivering 22o or 300 volts to the motors or other potentials suitable for incandescent or arc lamps. Transformers are rather expensive and their cost should, Of course. he consld- cred as part of the generating machin- cry.
 The principle of the reversibility of the dynamo finds no exception with alternat- ing currents. A machine similar to the generator can be used for the motor; un- fortunately however, such a motor might not always be self-starting. and the d. rect current necessary for its field mag netization might not always be available
 In some cases in which a feeble starting toraue existed the motor could be started
 without load and then the load applied through a friction clutch. Initially there might be sent over the line from the ex- citer in the generating station direct
 current that would charge set of stor' age batteries: current from this source
 would thereafter be available for excitinf the field magnets of the alternating-cur
 rent motor. and also temporarily for driv' ing its exciter as motor to speed up the | main armature; when under way thii small motor could by proper shifting oi switches become generator and ther
 supply current for field excitation and fol
 charging the batteries. Such alterators as were described in Article x were first
 employed in power transmissions; the | Westinghouse Company installed g mum ber of efficient and fairly satisfactory plants. This type of machine is known as the single phase"-that Is. there is but one circuit from the armature. terminal ing in two collector rings; at any instant a single impulse only of the current is in operation. and single wave repre- sents the varying values. Twice during each cycle. the current and power are zero; in this respect the case Is similar to that of a single crank engine, for twice each revolution there are 'dead' centers. Suppose two engines are arranged to have their shafts exactly in line and fit- ted with jaw clutches. so as at will to couple the two together. If one engine IS already running. the other engine must evidently be started and driven at not only exactly the same speed, but the jaws of the clutch must be in the right | relation. or. technically. in the same
 phase" then the connection between the ! two engines can be made without jar.
 The act of starting single-phase alter
 mating current motor Is similar; the gen orator Is already running, the motor driven by some exterior means until, as ? nearly as can be judged. the speed is sui fictent; a pilot lamp, or sort of telephon.
 connected both to motor and generator gives visual or audible evidence of th' | instant when exact equality of speed ana