Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 11 replies
  • Subscribers 34 subscribers
  • Views 1616 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Fixing a small motor

Chris Pearson

I want to fix an ancient 1/8 hp motor (Carter Electrical Co Ltd). As far as I can tell, the centrifugal switch has worn out, so that will be fun making a new one.

My question is what resistance seems reasonable for the coils. IR is good (well into the tens of megaohms) but they are a little dark and I would like to be confident that there has been no internal shorting.

The main coil is about 18 ohms and the starting coil 33 ohms. My maths tells me that the running current should be around 0.4 A. I cannot remember a lot about motors, but I realise that the impedance of the coils will be higher at 50 Hz than the (DC) resistance and that back EMF reduces the current. I hope therefore that the resistance values are about right.

Grateful for any reassurance!

Parents
  • 0

    1/8th hp? If we say that 1 hp is roughly 750w, then 750 divided by 8 gives something in the region of 90-odd watts, so work current back from that and see what your winding resistance readings say, or, is there a rating plate stating full load current etc still on the motor?

    Very rule of thumb I know, but to me your resistance readings don't asound far off in terms of future serviceability.

Reply
  • 0

    1/8th hp? If we say that 1 hp is roughly 750w, then 750 divided by 8 gives something in the region of 90-odd watts, so work current back from that and see what your winding resistance readings say, or, is there a rating plate stating full load current etc still on the motor?

    Very rule of thumb I know, but to me your resistance readings don't asound far off in terms of future serviceability.

Children
No Data

Community Rules & Guidelines