Maintenance Methods For Three-Phase Asynchronous AC Motors

Daily maintenance for continuously running three-phase asynchronous motors includes: visual inspection, checking if the fan is working properly and if there is any abnormal vibration, verifying the reliability of the coupling connection, ensuring the base is securely fixed, checking if the bearings are working properly (listen to the sound), and verifying the temperature (infrared thermometer). Regularly check the wire connections and switch contacts, and ensure the operating current is normal (clamp-on ammeter). For wound-rotor motors, also check the carbon brushes and slip rings.

Measuring Terminals

⑴ First, identify the two ends of each of the three-phase windings. Set the multimeter to the resistance range. Coils of the same phase will connect without resistance; coils of different phases will not connect. Therefore, the multimeter readings can distinguish which terminals belong to the same phase winding lead.

(2) To determine the corresponding terminals of the coil leads on both sides, set the pointer multimeter to the DC current range with the smallest range, connect the two terminals of any phase winding to the meter, and then momentarily touch the two terminals of the other phase winding to the positive and negative terminals of the dry cell battery. If the meter needle swings to a value greater than zero (i.e., clockwise) at the instant the dry cell battery is connected to the coil, then the positive terminal of the battery and the black probe of the multimeter are the corresponding terminals; otherwise, they are the opposite.