How to determine the direction of rotation of a DC motor before turning it on
In the absence of a circuit diagram and marking, the direction of rotation of the motor before it is connected to the network can be determined empirically. To do this, the armatures are connected to the clamps to a voltmeter of the magnetoelectric system with a scale of 3 — 7 V.
Slowly rotate the motor armature in the desired direction (clockwise or counterclockwise), note the greatest deflection of the instrument needle. Then the excitation coil is supplied with a voltage of 2 — 4 V 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 during the experiment.
For example, if the voltmeter of the magnetoelectric system is connected to the clamp «+» To the clamp Y1, the armature turns clockwise and the deviation increases, arrows appeared when the terminal «+» of the network was connected to terminals Y1 and Ш1, after this will make the motor rotate clockwise.