Fig. 2,806.—Wiring diagram and directions for operating Holzer-Cabot single phase self-starting motor. Location: The motor should be placed in as clear and dry a location as possible, away from acid or other fumes which would attack the metal parts or insulation, and should be located where it is easily accessible for cleaning and oiling. Erection: The motor should be set so that the shaft is level and parallel with the shaft it is to drive so that the belt will run in the middle of the pulleys. Do not use a belt which is too heavy or too tight for the work it has to do, as it will materially reduce the output of the motor. The belt should be from one-half to one inch narrower than the pulley. Rotation: In order to reverse the direction of rotation, interchange leads A and B. Suspended Motors: Motors with ring oil bearings may be used on the wall or ceiling by taking off end caps and revolving 90 or 180 degrees until the oil wells come directly below the bearings. Starting: Motors are provided with link across two terminals on the upper right hand bracket at the front of the motor and with this connection should start considerable overloads. If the starting current be too great with this connection, it may be reduced by removing the link. Temperatures: At full load the motor will feel hot to the hand, but this is far below the danger point. If too hot for touch, measure temperature with a thermometer by placing bulb against field winding for 10 minutes, covering thermometer with cloth or waste. The temperature should not exceed 75 degrees Fahr. above the surrounding air. Oiling: Fill the oil wells to the overflow before starting and keep them full. See that the oil rings turn freely with shaft. Care: The motor must be kept clean. Smooth collector rings with sandpaper and see that the brushes make good contact. When brushes become worn they may be reversed. When fitting new brushes or changing them always sandpaper them down until they make good contact with the collector rings, by passing a strip of sandpaper beneath the brush.
Rule.—To find the speed of engine when diameter of both pulleys, and speed of dynamo are given, multiply the dynamo speed by the diameter of its pulley and divide by the diameter of engine pulley.
Ques. How are the diameters and speeds of gear wheels figured?
Ans. The same as belted wheels, using either the pitch circle diameters or number of teeth in each gear wheel.
Figs. 2,807 to 2,809.—Wiring diagrams and directions for operating Holzer-Cabot slow speed alternating current motors. Erecting: In installing the motor, be sure the transformer and wiring to the motor are large enough to permit the proper voltage at the terminals. If too small, the voltage will drop and reduce the capacity of the motor. Oiling: Maintain oil in wells to the overflow. Starting: Single phase motors are started by first throwing the starting switch down into the starting position, and when the motor is up to speed, throwing it up into the running position. Do not hold the switch in starting position over 10 seconds. Starter for single phase motors above ½ H.P. are arranged with an adjusting link at the bottom of the panel. The link is shown in the position of least starting torque and current. Connect from W to 2 or W to 3 for starting heavier loads. Two or three phase motors are started simply by closing the switch. These motors start full load without starters. The motor should start promptly on closing the switch. It should be started the first time without being coupled to the line shaft. If the motor start free, but will not start loaded, it shows either that the load upon the motor is too great, the line voltage too low, or the frequency too high. The voltage and frequency with the motor running should be within 5% of the name plate rating and the voltage with 10 to 15% while starting. If the motor do not start free, either it is getting no current or something is wrong with the motor. In either case an electrician should be consulted. Solution: To reverse the direction of rotation interchange the leads marked "XX" in the diagrams. Temperature: At full load the motor should not heat over 75 degrees Fahr. above the temperature of the surrounding air; if run in a small enclosed space with no ventilation, the temperature will be somewhat higher.
Ques. What should be noted with respect to generator pulleys?
Ans. A pulley of certain size is usually supplied with each generator by its manufacturer, and it is not generally advisable to depart much from the dimensions of this pulley. Accordingly, the solution of the pulley problem usually consists in finding the necessary diameter of the driving pulley relative to that of the pulley on the generator in order to furnish the required speed.