Doerr Motor Problems

Hopefully I picked the right forum for thos question. I am in the process of rebulding a Doerr motor - 2 HP, 3450 RPM, single phase, capcitor start with a centrifugal switch, single voltage (220), 12 amp FLA.

I have been able to resolve a few problems but encountered another when I got it assembled and test ran it. When I flip the ON switch there is a sparking at the centrifugal switch - similar to what you might see with brushes. It occurs almost every time but not every time. The spark ranges from small to large. It is almost instantaneous (maybe less than 1 second) and stops very quickly as the motor comes up to speed. It appears to be located around the rotating piece of the centrifugal switch. It was sparking before I did anything to it but I attributed that to dirt/sawdust.

I've never noticed this sparking on other capacitor start/centrifugal switch motors I've worked on so I'm wondering if this is a normal occurrance or if I have more work to do?

Here's a somewhat poor video of the sparking. It took a few tries to get t to spark - as I said above it os pretty random. The spark is on the left side just above the reset button.

VID 218418 15581 - YouTube

So I'm wondering if 1) this is somewhat normal and, if not, 2) what would be the likely cause/fix?

Thanks for any thoughts you may have

Rick

Normal, the centrifugal switch is just breaking a connection and the angry pixies are trying to jump the gap.

dalmatiangirl61 said:

Normal, the centrifugal switch is just breaking a connection and the angry pixies are trying to jump the gap.

Click to expand...

That's as good as any explanation, and nicely original...I like it!

It's reasonably normal to see a spark. There is a substantial current flowing and breaking the circuit leaves a line of those angry pixies who are already running, so they have to try to jump.....(OK, it;s an inductive circuit, and the property of....... phooey, I.m going with the running pixies!)

Thanks guys - I had a recommendation on another forum that, while somewhat normal to see sparking, it might be worth the effort to clean the centrifugal switch contacts.

Rick

Well I took the motor apart again to clean the contacts. Still sparking but based on the comments I have received I'm going to call this "normal" and consider ths motor rebuild complete. Thabjs for the help!

Rick

Do Her motor problem
Look up how to dress electrical contacts
Never use emery paper
Fine diamond files work really well
Profile of the contact is important
How old is the starting capacitor?