There’s been a nice little motor in my project shelf for years while waiting for an application. Don’t know or can’t remember what it was off of. It may have come with its “run capacitor” but I’m not sure….and can’t find it if it did. Most likely, I rescued the motor off some outdated equipment heading for the scrap dealers 20 years ago or more.
The motor is a nice compact 1/3 HP PSC (permanent-split capacitor) type. There is no centrifugal switch, so the start winding stays energized with the capacitor full time. The thermal protection fuse can be seen wrapped up on top of the field windings. I’ll have to cut loose the motor leads to trace them back to see how they are configured. I want to add to and bring out both start winding leads anyway to make the motor reversible.
Yellow arrow points to capacitor value.
The question of the day: Notice the nameplate data listing the capacitor value of 300mfd (micro farads)!!! That seems unbelievably high for a permanent run capacitor in such a small motor?? Most are normally in the 10mfd to maybe 50mfd. Multiple cap’s could be parallel connected to add up to 300mfd but the bank of cap’s could be as big as the motor almost. There is no “decimal point” stamped in the nameplate value, either.
Does anyone know what application or motor of this type would require such a large run capacitor?? There seems to be no single capacitor of that size listed as a motor capacitor, oil filled.
Could a smaller cap be used instead without an excessive increase in current draw to the start winding? I’m sure starting torque would be reduced. I’d hate to let the magic smoke out of the start winding.
Believe the motor to be circa 1970s. I found a similar motor for sale online….listed as used. But there’s no pic of the capacitor and I’m betting they don’t even know that it requires an external capacitor to properly run.
Any and all ideas welcomed!!
The motor is a nice compact 1/3 HP PSC (permanent-split capacitor) type. There is no centrifugal switch, so the start winding stays energized with the capacitor full time. The thermal protection fuse can be seen wrapped up on top of the field windings. I’ll have to cut loose the motor leads to trace them back to see how they are configured. I want to add to and bring out both start winding leads anyway to make the motor reversible.
Yellow arrow points to capacitor value.The question of the day: Notice the nameplate data listing the capacitor value of 300mfd (micro farads)!!! That seems unbelievably high for a permanent run capacitor in such a small motor?? Most are normally in the 10mfd to maybe 50mfd. Multiple cap’s could be parallel connected to add up to 300mfd but the bank of cap’s could be as big as the motor almost. There is no “decimal point” stamped in the nameplate value, either.
Does anyone know what application or motor of this type would require such a large run capacitor?? There seems to be no single capacitor of that size listed as a motor capacitor, oil filled.
Could a smaller cap be used instead without an excessive increase in current draw to the start winding? I’m sure starting torque would be reduced. I’d hate to let the magic smoke out of the start winding.
Believe the motor to be circa 1970s. I found a similar motor for sale online….listed as used. But there’s no pic of the capacitor and I’m betting they don’t even know that it requires an external capacitor to properly run.
Any and all ideas welcomed!!
