Single phase motor start capacitor.

Hi all,

Quick question. I have an 230v anchor winch with a broken centrifugal switch on the motor which is letting the smoke out the start capacitor.

I’m having trouble finding a replacement centrifugal switch. So I was thinking of replacing it with a potential relay. Problem is these are not a common item in europe. So my next thought was to use an adjustable over voltage relay. However to do this I would need to know what is the back voltage that a traditional motor start potential relay is triggered at, anyone know?
Harris Marine...
1) There is no doubt that the Start-Capacitor has been damaged and must be replaced !
2) Since the Start-Capacitor has been "smoked", the Centrifugal-Switch has failed "closed" !
3) The good news is that the Centrifugal-Switch wire is available externally !
4) Install a Time-Delay-Relay that is energized when the motor is energized !
5) Wire the TDR's "times-open" contact, between the Centrifugal-Switch wire and the Start-Capacitor !
Regards, Phil Corso ( [email protected] ) Boca Raton, FL
Hi Phil,

Thanks for replying. I did think of a timer, however an anchor chain is a varying load so it will have varying startup times. Also the anchor can get caught at times so the start capacitor may need to re engage at times.
Harris Marine...
I'm sure the Centrifugal-Switch's "time to open" doesn't vary much. Obviously the acceleration-time does change due to different loading, but it's in the order of 1 or 2 seconds !
6) What's the rated Horsepower and Speed ?
7) Do you know how to determine when the Switch opens on any machine?
BTW, are you a USA Company?
Hi Phil,

Thanks for getting back to me.

The motor is 3,6kw so 4hp.

There is a secondary anchor winch that’s fully functional and I would estimate that the centrifugal switch opens at around a second. I also checked the back voltage before which is around 400v.

I am in Spain btw, not USA
Harris Machine...
Regarding my Q7... there are 2 ways:
1. Hold a large screwdriver or piece of wood, between the motors carcass close to the Centrifugal-Switch, and your ear. It takes a some of practice. bur in most cases the switch opening can be heard.
2. Place a clamp-on ammeter around either of the Start-Capacitor wires, if accessible
Regards, Phil
Harris Marine...
Here's another "Induction Motor Tip" !
Regardless of kW or HP size, any uncoupled induct'n motor, at rated name-plate voltage, should accelerate to full-speed in less than 5 seconds !
Phil Corso
Hi Phil,

Yes I checked by measuring the voltage across the start windings whilst operating the winch. The voltage quickly raises up to 400v then cuts out completely. The whole process takes approximately a second, give or take. I think we would see smoke if we waited 5 seconds.