Regulation by Shunt Field Resistance.--Since regulation by this method is for speeds above normal, a starter must be used to bring the motor up to its rated speed. Usually the starter is combined with the regulator, as shown in [fig. 761], the device being called a compound starter.
Figs. 763 to 765.--Holzer-Cabot shunt wound motor; diagrams showing connections and positions of index point for forward and reverse rotation.
LOCATION AND SETTING.--The motor should be placed in as cool, clean and well ventilated a location as possible, away from acid or other fumes which would attack the metal parts or insulation, and should be easily accessible for cleaning and oiling. Do not put it in some corner where care of motor will be neglected because of the trouble of getting at it. 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 much too heavy or too light for the work it has to do, as it will materially reduce the output of the motor. The belt should be about one-half inch narrower than the pulley.
ROTATION.--In order to reverse the direction of rotation, interchange leads A and B, and shift brush ring as shown in the diagram above.
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.--Before starting the motor see that the armature revolves freely, that the bearings are full of oil, and the oil rings are in place and free to turn.
Examine connections carefully to see that they are according to above diagram, after which proceed as follows:
1. Close the main knife switch. This action should not allow any current to pass through the motor (see Note 2);