How to Identify the Common Terminal of a Motor with a Multimeter
Method for Identifying the Common Terminal of a Motor with a Multimeter
Measure the resistance between each pair of the three terminals with a multimeter. The maximum resistance value is obtained when the main winding and auxiliary winding are connected in series. From this, the remaining terminal is the common terminal.
Once the common terminal is identified, it is easy to distinguish the main winding and auxiliary winding. The winding with smaller resistance to the common terminal is the main winding; the one with larger resistance to the common terminal is the auxiliary winding.
Set the multimeter to the ×1 ohm range, and measure the resistance between each pair of the three leads in sequence. When the measured resistance reaches the maximum value, the lead without a test probe attached is the common terminal.
How to Determine the Start and End Terminals of a Motor
Question: For a motor without a nameplate and with no markings on its six outgoing leads, how to identify its start and end terminals?
Answer:First, use the resistance range of the multimeter to separate the three winding groups. Then switch the multimeter to its minimum DC voltage range. Connect the two test probes to the two leads of one winding. Select one of the remaining two windings, connect a battery and make momentary contact. Observe and record the deflection direction of the multimeter pointer. Move the multimeter probes to the other winding and repeat the above procedure.
If the pointer deflects in the same direction in both tests, the leads touched by the same test probe (red or black) on the two windings are the
like terminals.
Replace the battery connection to the other winding group, and use the same method to identify the leads of the third winding.
How to Identify the Common Terminal of a Motor
Set the multimeter to the ×1 ohm range, and measure the resistance between each pair of the three leads in sequence. When the measured resistance reaches the maximum value, the lead without a test probe attached is the common terminal.
How to Identify Like Terminals of a Motor
First, use the resistance range of the multimeter to separate the three winding groups. Then switch the multimeter to its minimum DC voltage range. Connect the two test probes to the two leads of one winding.
Select one of the remaining two windings, connect a battery and make momentary contact. Observe and record the deflection direction of the multimeter pointer. Move the multimeter probes to the other winding and repeat the above procedure.
If the pointer deflects in the same direction in both tests, the leads touched by the same test probe (red or black) on the two windings are the like terminals.
Replace the battery connection to the other winding group, and use the same method to identify the leads of the third winding.
