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520 HANDBOOK OF PROJECTION FOR
Mechanically the multiple generator is the same as the series type, the difference being electrical. The generator field is compound wound, the curve being held as flat as possible and the points of single and double arc are kept as nearly as possible at the same voltage level.
On the smaller units this voltage is about 85 maximum and on the largest ones, it is from 90 to 95 volt maximum.
The diagrams shown illustrate very clearly the general method of wiring which follows the usual practice of wiring any constant potential system. A departure from this, however, is /gaining favor in houses where two generators are installed. This is accomplished by running a set of buses from each generator into the panel. Between these buses are double throw double pole switches wired to the various pieces of current consuming apparatus. This arrangement results in the projectionist being able to throw any piece of apparatus on either generator and it is meeting with much favor.
To start the multiple generator the switches to the load should all be open. Start the motor and observe that the generator builds up. When excited, close the switch controlling the arc to be operated and strike it. If the voltage of the generator is not correct when the arc has been struck, it should be corrected. It can then be loaded to its capacity.
The multiple machines are made regularly in sizes from 20-40 to 200-400 amperes and larger to order.
GENERAL CARE. — Keep the machine clean. Do not use sand or emery paper on commutator. Should the commutator become dirty, hold a piece of coarse canvas or cheese cloth firmly against its surface while machine is running, and when free of dirt, wipe the surface with a clean cloth pad, moistened very SLIGHTLY with pure vaseline. See Section C, general instructions No. 7.
Do not permit the brushes to become too short. If you do, disastrous sparking will result. A new set of brushes should be put in before the eld ones are entirely worn out. Instead of putting in a new set all at one time, it is better to put in two first, one in each holder, and at opposite ends of commutator. Run that way until the new brushes have worn to a perfect fit, whereupon you may replace the other worn brushes with new ones.
The grease cups on the machine should be given onenaif turn once every two (2) weeks. If this is done these cups will not require refilling for a number of months.
WHEN ORDERING PARTS FROM MANUFACTURER ALWAYS GIVE NUMBER ON NAME PLATE OF THE MACHINE.