Stumped by 1/3 hp Motor
#3
  
This is embarrassing The machine was seldom used, sat outside covered by a tarp. Always ran in the past at the flick of a switch. But this time it only hummed. I found it would start if given an assist. But then it would trip the automatic overload after a short time. Should be an easy fix I thought. I spent my career in industrial maintenance, including all sorts of sophisticated equipment: large three phase motors, inverters, DC motors, and synchronous motors to 1500 hp, etc. So this little fella should be a snap to fix. No capacitor to go bad so its obviously the centrifugal switch.

Disassembled the motor and could find nothing wrong with start contacts or the centrifugal device on the rotor. I noticed corrosion on the connections for the overload. Since my clamp on ammeter had shown no overcurrent (5.6 amps, full load rating 6.4 amps) I decided to bypass the Klixon OL. Now the motor occasionally hums and fails to start, but most of the time it starts but almost every start it reverses direction of rotation from that of previous start. Motor nameplate says motor in non-reversible. I should mention there is no sign of overheated or damaged windings.

Been retired now for almost 22 years and perhaps the gray matter isn't what it used to be. Anyone have any ideas what the problem with the motor might be?
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#4
  Re: Stumped by 1/3 hp Motor by HomerLee (This is embarrassing...)
(10-12-2018, 11:14 PM)HomerLee Wrote: This is embarrassing The machine was seldom used, sat outside covered by a tarp. Always ran in the past at the flick of a switch. But this time it only hummed. I found it would start if given an assist. But then it would trip the automatic overload after a short time. Should be an easy fix I thought. I spent my career in industrial maintenance, including all sorts of sophisticated equipment: large three phase motors, inverters, DC motors, and synchronous motors to 1500 hp, etc. So this little fella should be a snap to fix. No capacitor to go bad so its obviously the centrifugal switch.

Disassembled the motor and could find nothing wrong with start contacts or the centrifugal device on the rotor. I noticed corrosion on the connections for the overload. Since my clamp on ammeter had shown no overcurrent (5.6 amps, full load rating 6.4 amps) I decided to bypass the Klixon OL. Now the motor occasionally hums and fails to start, but most of the time it starts but almost every start it reverses direction of rotation from that of previous start. Motor nameplate says motor in non-reversible. I should mention there is no sign of overheated or damaged windings.

Been retired now for almost 22 years and perhaps the gray matter isn't what it used to be. Anyone have any ideas what the problem with the motor might be?

It is a start winding issue like you were going after.   Maybe  try an ohmmeter to see where it is not making a connection.   Did you check that the mechanical part of the centrifugal switch is operating freely. Also check the start winding continuity.   The non reversible part on the name plate means the winding leads to reverse it were not brought to a terminal box.    With no start winding in the picture if you spin the motor it will spin in either direction as it is doing.   Roly
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