-- Capacitor start motor. Starts and runs in either direction as it pleases. Capacitor good (replaced with others as test) 2 windings. Run winding across line voltage, Start winding across line voltage with capacitor in series. What determines rotating direction when starting?? This is on a small Delta
9 inch bandsaw. Both windings ohm out OK.
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.
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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?).
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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"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P
Right, has to be an open start winding or something along those lines. The direction is determined by the physical winding placement.
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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:
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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"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P
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