What makes a motor "suitable for variable speed control"

[Billgas]

Motor information is
GE 1000HP 4000V
MDL. 8313783302
Code G
Type K
Insulation F
No. 830897


How can I determine if this motor is "suitable for variable speed control"

 

[jraef]

While there are motor designs specifically suited for VFD use in low voltage low to medium power, once you get into this realm, most motors are built to order. So the only people who can answer that question will be GE, the manufacturer. Even then, they will want to know a lot of details about the VFD in question.

That said, some MV VFDs are designed with this issue in mind and are touted as being suitable for use on virtually any AC motor. The reason is, once you get in to something that expensive, mitigating the potential problems the VFD might pose to an existing motor becomes an insignificant added cost, so it becomes part of the selection and design criteria.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[DickDV]

To embellish jraef's comments a bit, if you spend enough money on conditioning equipment, VFD power can be converted back to pretty good sine waves so the motor insulation has very little extra stress. You do, however, have thermal issues in the motor as it slows down and conditioning equipment does not completely eliminate those.

 

[lansford]

In general;
Bearing lube at low speed
Critical speeds
Max speed
Insulation srength due to Harmonics
Fan cooling at low speed
JIM

 

[dbaird]

FYI....
Review NEMA Guide MG1 Section 12: "Application Considerations for General Purpose Design A and B Induction Motors used with Adjustable-Voltage or Adjustable-Frequency Controls or both."



David Baird

Sr Controls Designer
EET degree.
Journeyman Electrician.