DJ20 Start Capacitor

[Kevin Wilson]

I installed a longer cord on my DJ20 (10ga) and when I plugged it in for the first time the motor would not reach full RPM and had a hard time starting up. I checked all connections twice and the now the start capacitor. I was surprised that it has a 125VAC capacitor rated at 710-850 MFDs. It didn't test anywhere near that at 450. Is there anything I would have done or is this an unfortunate coincidence? Is it common to "boost" just one leg on 240V motors?

Thanks!

Kevin

[Rod Sheridan]

Kevin, always check the wiring after making changes, errors are far more common than coincidences.:D

It's possible a wire has become disconnected.

A dual voltage single phase motor (120/240V) has three windings,

Run winding #1

Run winding #2

Start winding #1

Note that all three windings are 120 volt


To run the motor as 120 volt, all three windings are in parallel.

To run it in 240V both run windings are in series, and the start winding is in parallel with one of the run windings.

The start capacitor is in series with the start winding, and since it's in parallel with one of the windings, it doesn't see the 240 volts applied to the motor.

That's why the start capacitor voltage rating is lower than the line voltage of the motor.

Regards, Rod.

[Kevin Wilson]

I'm baffled. All I did was install a longer cord and now I have issues! OK. I checked the cord at the plug and the connection at the mag switch. I have 240V on both sides of the switch with the switch engaged. I replaced the start capacitor but still get the same result. Motor attempts to start and only turns relatively slowly. I want to believe it has something to do from the power side connection at the switch back to the plug as that makes the most sense, but it all appears to be correct. Green to ground on both ends. White to white and black to black. I'm sure it is starring me in the face and I just don't see it!

Kevin

[Bruce Wrenn]

You could have 220 at the switch, and still have a bad connection. Because your VOM pulls so little current, there would be little or no voltage drop. Measure voltage when motor is trying to start. In worst case, put old cord back on and check results. If motor then starts, then problem is in new cord set. Remember when working on something the difference between "champ" and "chump", is "U". I know, trust me I know.