How to label the terminals of DC motors

Marking the output ends of DC motors current

How to label the terminals of DC motorsAs an example, consider marking the output ends of a DC machine with a mixed field.

To determine the output ends of individual windings (series C1, C2, parallel Sh1, Sh2 and armature Y1, Y2 with additional poles D1, D2), you must have a test lamp or voltmeter and a source of alternating current. Whichever of the three coils, when touched, the lamp burns dimly, will be a parallel (shunt) coil.

The lamp will not light when one end touches the collector of the machine and the other to the terminals of the series coil, and will light when it touches the coil terminals of the auxiliary poles connected to the armature.

How to determine the direction of rotation of a DC motor current before turning it on

In the absence of a circuit diagram and marking, the direction of rotation of the motor can be determined empirically before connecting it to the network.

To do this, a scale 3 magnetoelectric system voltmeter is connected to the armature clamps. — 7V.Slowly rotate the motor armature in the desired direction (clockwise or counterclockwise), note the greatest deviation of the instrument needle.

Then a voltage of 2 — 4 V is applied to the excitation coil from a flashlight battery or a battery of such polarity that the deflection of the voltmeter needle increases. Note the polarity of the battery connected to the field terminals and the polarity of the voltmeter connection to the armature terminals. When connecting to the mains, observe the same polarity. The direction of rotation of the motor will correspond to the direction of rotation in the experiment.

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