Clue me in on this.

070704 2133 - Warren Weber posted:

The motor should start and run in only one direction. My first thoughts are that the starting relay in the motor is either stuck, or the contacts are dirty. You will probably have to take the end bell off the motor and check out this relay. It works on a centrifugal principal: as the motor speeds up, the relay opens and removes the capacitor and start windings from the circuit.

Slight correction. A capacitor start motor may run in either direction but the winding used for starting should only start it in one direction with a given wiring arrangement. This is determined by the placement of the capacitor and the physical construction of the motor.

--- sam | Sci.Electronics.Repair FAQ:

Repair | Main Table of Contents:

+Lasers | Sam's Laser FAQ: | Mirror Sites:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

NO start switch. ???

See if there is any torque during starting. I bet there is none and little load, so it starts either direction at random. The circuit to the starting winding is not being energized or the start capacitor is open (but you said you checked this?).

--- sam | Sci.Electronics.Repair FAQ:

Repair | Main Table of Contents:

+Lasers | Sam's Laser FAQ: | Mirror Sites:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

If there's no start switch, it's a permanent split capacitor, or PSC motor. Never seen one that would run in either direction without changing the wiring though. Normally you swap the phase of one winding to reverse.

I had a machine with a reversable capacitor start 1 HP motor. I found that if you switched the direction without stopping the motor, the inertia of the machine would cause it to keep on running in the original direction despite the winding mismatch.

--
Joe Leikhim K4SAT (this posting in DSB to placate the KOOKS)
"The RFI-EMI-GUY"©

Right, has to be an open start winding or something along those lines. The direction is determined by the physical winding placement.

--- sam | Sci.Electronics.Repair FAQ:

Repair | Main Table of Contents:

+Lasers | Sam's Laser FAQ: | Mirror Sites:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Yes, because that probably has a centrifugal starting switch which disconnects the starting winding entirely when at normal speed. So, the direction changing switch has no effect until it goes down to below about

75 percent of normal speed.

--- sam | Sci.Electronics.Repair FAQ:

Repair | Main Table of Contents:

+Lasers | Sam's Laser FAQ: | Mirror Sites:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Thanks for all of the replies. Just a cap start motor. 1 cap 2 windings. As shown on #5 that charles sent. Did ohm out per diagram. May be a shorted start winding. This is a band saw motor (Delta) Price on motor almost same as price of saw. (9 inch saw). Owner will replace saw. TIA. WW

Makes sense

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©