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488 HANDBOOK OF PROJECTION FOR
The Hallberg D. C. to D. C. motor generator is also made in a new, more modern design, illustrated in Fig. 166. This machine has only two bearings, both of which are ball bearings. The various machines have outputs ranging from 25 to 150 amperes. With this type of motor generator the manufacturer will furnish controller panels, including the necessary voltmeters, and ammeters for double arc operation where the generator capacity is 70 amperes or more.
INSTRUCTION NO. 1. INSTALLATION.— (See General Instruction Nos. 1 and 2.)
INSTRUCTION NO. 2. CONNECTIONS^All electrical connections should be made as shown in the wiring diagram accompanying each machine, and they must be clean and tight. Fuses should not have a higher capacity than that indicated by the diagram.
INSTRUCTION NO. 3. BRUSH TENSION.— After the machine has been properly set and connected, rotate the
armature by hand and examine each carbon brush to make sure that it moves freely, without the slightest friction, in the brushholder. Make sure that the flexible copper cable, or pigtail as it is called, is properly clamped b y the screw in the brushholder casting. .When Figure 166. the brush moves freely
in the holder, the next
thing to receive attention is the tension spring which holds the brush against the commutator. See General Instruction No. 8. The pressure exerted by the brush tension spring may be varied by changing the end of it to different notches provided in the brushholder casting. Any required degree of tension can be had by using the different notches.
INSTRUCTION NO. 4. OILING— The oil chambers should contain enough oil to give the rings (see Fig. 148) a good dip. The oil level may be seen in the gauge on the sides of the bearings. It should be at the top of the gauge. When starting the machine, lift oil chamber covers and see that the oil rings are turning freely and carrying oil to the shaft.