Figure 14-31. - Testing for an open winding with a ohmmeter.
Watch the digital readout in the meter as the check is made. Each reading should appear to be approximately 0 ohms, since winding resistance is usually less than 10 ohms. If, during the check, the resistance digital display remains blank (infinity), an open or break exists.
The procedure for carrying out a voltmeter test is as follows:
Ensure the power is on and all wires are properly connected to motor terminals.
With the voltmeter set on the proper scale, place the leads across the R- and C-terminals.
Read the voltmeter.If the motor shows line voltage, the motor is energized and should be operating. The connections are similar to that shown in figure 14-31.
The procedure for conducting a test lamp continuity check is as follows:
A simple test lamp consisting of a power circuit plug, two flexible insulated wires with clip leads, and a 25-watt socket with a bulb is used. Figure 14-32 shows the test lamp procedure.
Ensure the power is OFF, discharge all capacitors, and remove the motor terminal wires.
Make a continuity test through both windings by attaching clips across the C-terminal, then do the other terminals one at a time. Now plug the test lamp into a receptacle. If the bulb fails to light, there is an open winding.
In an electric motor the winding turns lie side by side with only the insulating varnish separating one loop from another. When one loop of the copper wire contacts another, the
Figure 14-32. - Testing for an open winding with a test lamp.Continue Reading