vfd's

[manofsteel2616]

I have a question concerning variable frequency drives. When hooking two or more motors to one drive, would you use external overloads for each motor or is there another way to protect the motor? I wouldn't think one would want to use the parameters because they would have to be set high to cover all of the motors connected. For example, motor a's ol's are set to two amps while motor b's ol's are set at eight amps. I would assume the parameters would be set at 10 amps but if motor a was the only one running, the ol's wouldn't trip until 10 amps when it was rated for 2 amps. Are my assumptions correct or am I in left field? Thanks

 

[RETRAINDAILY]

yes each motor needs it's own

 

[mcclary's electrical]

I have a question concerning variable frequency drives. When hooking two or more motors to one drive, would you use external overloads for each motor or is there another way to protect the motor? I wouldn't think one would want to use the parameters because they would have to be set high to cover all of the motors connected. For example, motor a's ol's are set to two amps while motor b's ol's are set at eight amps. I would assume the parameters would be set at 10 amps but if motor a was the only one running, the ol's wouldn't trip until 10 amps when it was rated for 2 amps. Are my assumptions correct or am I in left field? Thanks

Each motor needs to be protected aeperately. I did (2) Drive panels in a Fan Lumber Drying Building. There were 32 ( 5 ) hp motors on each end of the building. One drive started all 32 motors. 64 motors total. Each one has it's own overload block

 

[ptonsparky]

I have a question concerning variable frequency drives. When hooking two or more motors to one drive, would you use external overloads for each motor or is there another way to protect the motor? I wouldn't think one would want to use the parameters because they would have to be set high to cover all of the motors connected. For example, motor a's ol's are set to two amps while motor b's ol's are set at eight amps. I would assume the parameters would be set at 10 amps but if motor a was the only one running, the ol's wouldn't trip until 10 amps when it was rated for 2 amps. Are my assumptions correct or am I in left field? Thanks

Not sure if you are actually going to use two motors of different HP or that was just your example.

I believe all the motors controlled by one VFD are supposed to be of the same type. HP, RPM, etc.

 

[stevenj76]

The only way I have seen it done is IEC style, with the bus bars and starters tapping off for each individual motor.

I am sure a smart man could fake it and make it, but something like that should be on a stamped drawing for your own protection.

 

[Besoeker]

Not sure if you are actually going to use two motors of different HP or that was just your example.

I believe all the motors controlled by one VFD are supposed to be of the same type. HP, RPM, etc.

I don't know if there is any code or regulation that requires that but, unless the motors are to be mechanically coupled together, there is no technical constraint that prevents motors of different rating being run from the same drive.