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532 HANDBOOK OF PROJECTION FOR
is at N the armature will not rotate at all, it being the neutral point. It therefore follows that in order to reverse rotation you have only to loosen the rocker-ring holding set-screw and move the ring to the position desired, as above indicated.
ADJUSTMENT — After you have the set running well, adjust the generator field rheostat (Manufacturer's recommendation) until the voltmeter reads approximately as follows :
75 volts for 2% Kw. 30 amp. generator
75 volts for 2^4 Kw. 36.7' amp. generator
75 volts for 3 Kw. 40 amp. generator
75 volts for 4 2/5 Kw. 55 amp. generator
80 volts for 5% Kw. 70 amp. generator
80 volts for 5^4 Kw. 72 amp. generator
90 volts for 81/10Kw.90 amp. generator
,100 volts for 11 Kw. 110 amp. generator
STRIKING ARC WITH SINGLE ARC EQUIPMENTS—
For single-arc equipments the switch which short circuits the ballast resistance, (rheostat) (Figure 161), should always be opened before striking the arc. Strike the arc in the usual way by bringing carbons into contact and immediately separating them. Then close the short-circuiting switch and adjust arc length until voltmeter reads as follows :
Amps, at Voltmeter
Arc Reading
30 .o 55
36 ., 56
40 .................57
55 ....................60
72 . ... 63
90 ..65
110 ........67
140 ....69
200 72
250 73
Note : Above is manufacturer's recommendation. Experienced projectionists may vary from it reasonably, if results are improved by such variation.
If when voltage is adjusted, the ammeter does not show desired reading, and generator is not producing up to its capacity, adjust ballast resistance to increase or decrease the