Series Wound Motor Test Procedure

The basic electrical connections for a series wound motor are relatively simple. This guide not only demonstrates the test procedure for a series would motor but the connections used in this procedure are the same used in normal operation of the motor. While written for electric vehicle motor testing, this test can be used on any series wound motor...be sure to adjust the voltage according to the size of the motor. For an unloaded motor, such as in bench testing, you should never apply more than 20% of the rated voltage to avoid over-speeding of the armature and even then USE CAUTION!!!

Electric Motors generate a tremendous amount of torque. Secure the motor carefully
otherwise them motor may violently move (counter-rotate)!!!

For "bench testing", or while operating unloaded for testing and/or seating brushes, forced air cooling is not needed. A switch is not required for this procedure however when making the final connection expect some electric sparking. To prevent damage to the terminal of the motor and/or cabling consider using a heavy duty switch or contactor.

To check that the motor is operational, connect the negative terminal of a 12 volt battery (for 96 volt motor) or 6 volt battery (for 48 volt motor) to the "S2" terminal of the motor. Connect the positive terminal of the battery to the "A2" motor terminal. With the motor held down, connect a jumper wire (strap) between terminals "A1" and "S1." The idling motor will probably draw about 20 Amps from a charged battery. The motor will turn in a clockwise direction as viewed from the shaft end.

    DO NOT apply more than the recommended voltage to an unloaded series motor as it can easily over speed causing a great deal of destruction. Maximum armature speed for most motors (including the CitiCar/ComutaCar motors) is 3600 rpm with a normal operating RPM of 3000 RPM.

    Proper shop safety precautions should be exercised when testing any electrical device including eye protection, gloves and no loose fitting clothing just to name some. DO NOT connect anything to the motor shaft as the motor develops very high torques. These motors can provide in excess of 1 foot pound of torque per amp of draw - a locked rotor can draw up to 900 amps! Be sure your motor is securely held down for all testing.

Note: The motor used in many of the CommutaCars do not have front bearings! They use the bearing in the differential to support the armature. A special adapter must be used to bench test these motors.
 

Important: Use caution, in addition to the high current that motor are quite capable of drawing when operating properly, a damaged motor can act much like a short across the battery. It is important to utilize proper safety techniques when working around motors, batteries and electricity. Don't forget to guard against shock hazards. Batteries also produce hydrogen which can create an explosion hazard. BE CAREFUL!

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This Home Page was created April, 1997
Most recent revision November 05, 2006