Motor Swap Considerations

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Saturn_Europa

Saturn_Europa

Senior Member
Location
Fishing Industry
Occupation
Electrician Limited License NC, QMED Electrician
This is a pretty basic question, but better then a big mistake. I am ordering a 20 HP motor to be shipped to Alaska.


Current Motor: 460v, TEFC, 256TC, 1755 rpm, 20 HP

New Motor: 460v, TEFC, 256TC, 1770 rpm, 20 HP, Inverter Duty


Are there any other considerations? All shaft sizes on 256TCs are the same, correct? Is there any concern about the nominal difference in RPM?

I've been reviewing this document and think, I am good to go. But I always like a second opinion.
 
Frank DuVal said:
1755 vs 1770 might be realated to better efficiency, i.e. less drag, so new one better. Inverter rated good too.
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Higher RPM at rated load does suggest better efficiency. Drag won't be a consideration. Starting and inrush currents will likely be higher; ensure the starter overloads won't have problems or at least that it still has overloads available if you need to change class or size.
 
Jraef said:
Inverter duty motor implies it is going to be controlled by a VFD? If so, don't worry about the slight difference in RPM at rated load, the VFD is controlling that anyway.
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These days most motors are VFD rated whether they have a VFD on them or not, at least for three phase. Some exceptions for low cost and very small motors but you would have a hard time going to the motor store and getting a generic 5 horsepower 480 volt motor that was not VFD rated these days.
 
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