Drill press motor not starting or starting in reverse

[stupoty]

Hello,

My drill press is developing a fault intermitently.

Sometimes when you hit the go button the motor just buzzes , if you losen the belts the motor starts but backwards.

The motor is a capacitor start single phase motor.

Time to swap the cap or is this indicitive of some other fault?

Stu

 

[Lo-Fi]

Given the intermittent nature, I'd look at the centrifugal switch. Maybe dirty or worn out contacts.

 

[markba633csi]

Could be the cap, the internal switch, or even a winding fault
My money is on the internal C switch also
Does the motor have a lot of hours on it?
I would begin by testing or replacing the cap- do the easiest thing first

 

[jbobb1]

I second the centrifugal governor. Sometimes a few taps on the opposite drive end of the motor with a rubber mallet will temporarily free it. You'll usually hear it. It's a free test.

 

[markba633csi]

Usually the switch contacts wear out or the mechanism breaks from all the thousands of start cycles

 

[jbobb1]

You'd be surprised the number of dirty stuck governors I had seen in the 10 or so years I had worked on single phase motors. I agree though that the switch is most likely the culprit.

 

[stupoty]

Thanks for the input, I'm going to take the motor off and open it up.

Will post progress

Stu

 

[stupoty]

Switch seams free moving.

Capacitor measured in the nano farads (50nF) range not the 150 micro farads thats on it.

Weirdly it's also 110v , the motor is 240v.

Hummmm.

Stu

 

[markba633csi]

Stu: AC motor's windings are usually arranged so that the cap only sees 110 volts even on a 220 volt supply
Sounds like the cap is bad for sure- good work Holmes!
If you can stuff a higher voltage cap in there it will last longer but the physical size increases with voltage and uF rating.
Keep the value at 150 microfarad but try to go a little higher than 110 volts (I think 125 is the next size up)
-Mark

 

[RJSakowski]

Stu: AC motors are usually arranged so that the cap only sees 110 volts even on a 220 volt supply
Sounds like the cap is bad for sure- good work Holmes!
If you can stuff a higher voltage cap in there it will last longer but the physical size increases with voltage and uF rating.
Keep the value at 150 microfarad but try to go a little higher than 110 volts (I think 125 is the next size up)
-Mark

I know this is true for dual voltage motors but this true true single voltage motors? Stu is in the UK where 120 volts is not an option. I have a single voltage motor rated for 208 volts and ir has a 220 volt a.c.,145 mf capacitor. I would replace with a 240 volt capacitor even if it meant a lower capacitance. It may start slower but it will start. Once running, the start winding drops out so there is no effect on operation.