Document 3JBbMMRvrLg6N8pkb174O6kga

of a dc voltage proportional to pcid. M1 topefy- - - | Control U- At tufifi/f to/toft (Wawste - J Grid JS treostOMHf 9 primorf*^^3 , otwvt.V reoctm ftPtsijtor \ To l/lf/Wi'f roQvtotor---~ yxiffoto oena * gtU trontfoerntr 7Phott-thift network for thyrotfon-tubo grid control. Sketch to right shows how volue of resistor ond reoctor vory phase onglo of the grid transformer voltage Grid circuit of thyrotron rectifier. Vorying phase angle of grid voltooe, by mothod shown in Fig. 7, determines value of onode current supplied to field current-limit control on speed control to limit rate of speed change. AmpUdyne Control. An atnplidyne (separately excited dc generator) may be used as regulator, amplifier or ex citer. Because of its high speed of response, high amplification and low power level required to excite its control fields, an omplidyne is used for excita tion of generator fields in adjustable voltage systems. Principal circuits of sueh a system are shown in Fig. 3. An exciter set, consisting of' a squirrel-cage driving motor, a constant-voltage exciter and an omplidyne, furnishes regulated dc con trol power ond adjustable excitation for dc generator field. Field of shunt motor driving the lood is generally excited at a constant rate. System is able to produce constant torque over o 10 to I speed range. By field weakening of. shunt motor, on addi tional 4 to 1 speed range can bo obtained. A tachometer generator coupled to the dc motor measures Its actual speed, producing a speed signal in the form This speed signal Is fed into on elec-, ironic speed regulator ond compared to o standard established on a ipeed-setyu potentiometer. Any deviation between speed signal and stondard sets on the omplidyne fields to effect a change la'dr generator voltage. *, Three fields control omplidyne ontpat voltage: Boost field F-- F, is excited'it a constant rate in a direction to rabedc motor speed. Buck fields F,--F, op poses boost field; Its excitation Usd- justed by regulator. Net diflereace to magnetomotive force of the two falds- determines amplidyno voltage and thos motor speed. Antihunt field Fi--Fi I* connected to omplidyne tennipJ through a capacitor. Its exeitstlen proportional to rate of change of impl dyne voltoge, snd its polarity fs welt to oppose nny change in amplifr*? voltage. .1 Speed Regulator. One simple W*} of speed regulator, combining fuDCtl*, of speed and current limit control, shown In Tig. 9. This regulator coni tsins four high-vacuum tubes fw*L an electronic amplifier. Only cant control circuits ore shown, * . X simplicity details such as cathode ors, screen ond suppressor Rr~* grid feed-back circuits are o'uei . Desired speed is mi on a P1 meter-type speed setter e* across regulated dc control Tachometer generator voltage " into a resistor and balanced sgsi*' stondard. Difference between speed and the standard deterw . lential of grid, point 3 of ' (| thus amount of current Pwe" j 1 and potential of plnte, P*1; regarding tubes 2 ond 3 for fan grid point 5 of tube 4 vanes IOO (704) POWER No--'f t 5 Wiring termlnotcs In box locoted on the for side. Combi- C Some unit os in Fig. S, disossembled. AmpUdyne ormoturo notion motor ond omplidyne simllor to units shown in Fig. I V is conventional while field resembles induction motor itotor /point 4, thus affecting amount of cur'.rent passed by tube 4, serving to excite .buck field F--F, of omplidyne. If (speed setter is adjusted for higher speed, tachometer voltage no longer baJinces standard. Pofnt 3 then be'.comes more positive and tube 1 passes* more current. As b result points 4 and ' 5 become more negative, tube 4 poises leas current, and field,F,--F, becomes weaker. This change Is followed by a rise in tmplidyne voltage increasing dc motor ... ipeed until a balance between speed sod the standard is reestablished. Tubes 1 and 4 form an amplifier so regulator responds to small deviations between Mtual speed ond standard (such as peed drop due to load) starting cor rective action. ' re used for current-limit control wperimposed on speed control. Theii eoatro) grids are connected to a poten ,J*e,er college across being propor Wjf to drop across commutating field; ;,.c molor "d generator. This drop ` me--s-s--u-re voif the ccuurrrreenntt nfloowwming ii iinnft,,re *p clrcuil. and thus I E'0"*! ' ') Screen grid, o anrit j *nd 3' trough o positive bio wits 10 ,^em so. adjusted the late. ,.*LCU!7?nl in motor urmo ,0^d w H*"* ofF ttnd ,ube 3 1 Wuw 7` ejrcQf! .currcn* flowing in loot d [eclion of arrow, point 6 i: ^- .h,,.P,CMopoinl2. Whtl celeratl Ur,ent 1P circuit durinj limit . approaches eommutaiini Point 7 0j , . and| consequently, grit `k** tub* x Ub 3 become so negalivi 3 *^*8 been *>DMe* ^e#* current. Poin 4'Pue* n.mM more positive ond lubi To current than the speec >1* November 1940 Simple regulotor combining speed ond current limit control. Stondord, deter mined by speed setter. Is balanced ogolnst voltoge from tochometer generator seller calls for, resulting in molor speed increasing slowly. Thus lube 3 pre vents too rapid acceleration. Tube 2 is not affected os it le already turned off. When speed setter is turned to call for deceleration, current flow in loop circuit reversea, point 6 becoming posi tive with respect to point 2, end poten tial of points 7 end 8 rises. This con dition has no effect on tube 3, which is olready turned on. Tube 2, however, starts conducting when loop circuit cur rent approaches commutating limit and point S becomes more negotive. Tube 4 then carries less current than speed setter calls for and motor speed is re duced slowly, tubo 2 preventing too rapid deceleration. White function of regulotor has been described under assumption that man ual adjustment of speed setter sets de sired speed, it would be possible to introduce program control of speed by operating this setter outomatically. Thyrotron Exciters. An all-electric type of speed control has been developed in which thyrotron rectifiers rcploee the exciter set. Fig. 4 shows principal cir cuits of an adjustable-voltage system (Continued an page 136)' (705) 101