The single phase rotor test is one of the easiest ways to inspect a squirrel cage rotor for open bars. The test can be performed quickly and easily during the initial inspection of a motor preceding disassembly.

Use your test panel (or other AC source) to apply approximately 1/4 rated voltage across two phases. Slowly rotate the rotor by hand while monitoring current. Current fluctuation less than 1% usually indicates a good rotor. Marginal results range from 1% to 3%. If you see higher than 3% fluctuation, it is likely that you have an open rotor bar.

If you have questions about this test or need a bad rotor repaired, call (256) 352 5150 and we'll tackle the job for you.