Two Speed to VFD?

[Mike01]

Can a standard 2-speed / 1-winding motor operate on a single VFD? The thought was to abandon the low speed connect the VFD to the high speed only and set the max. min to a level where the motor will still self cool, add reactors to the drive output to help with the non-inverter rated motor. The end user does not have the funds avaliable to replace the motor as well however understands that by doing this it may shorten the life of the motor insulaiton and bearings. Does anyone have experience with this?

 

[Besoeker]

Can a standard 2-speed / 1-winding motor operate on a single VFD? The thought was to abandon the low speed connect the VFD to the high speed only and set the max. min to a level where the motor will still self cool, add reactors to the drive output to help with the non-inverter rated motor. The end user does not have the funds avaliable to replace the motor as well however understands that by doing this it may shorten the life of the motor insulaiton and bearings. Does anyone have experience with this?

As I said in another thread, I've heard of but not personally come across bearing failures. Good installation practice helps.
On the other hand, Ive seen winding failures on a number of motors. The output reactors help in this respect.

I don't know how the two speeds are obtained but if the motor has the same power rating at both speeds the torque available will be higher on the low speed. You won't get that torque if you connect the VFD for high speed.
It may or may not matter depending on your application.

 

[Jraef]

As Besoeker says, it's important to know up front exactly what TYPE of 2 speed motor you have, there are 3 possibilities. It will be either Constant HP or Variable Torque or Constant Torque. You need to look at the nameplate to be sure.

1. If the nameplate says the HP is the same at either speed (or does not give a different HP rating), then it is Constant HP and you might need to reconsider how you use the VFD.
2. If the nameplate says that the low speed HP is 1/4* the high speed HP, then it is a Variable Torque application and your plan is valid.
3. if the nameplate says that the low speed HP is exactly 1/2 of the high speed HP, then it is a Constant Torque motor application and your plan is still valid.

* If the motor comes from Europe (Dahlander motor), the HP ratio may be different.

Beyond that, invest in a good motor output filter from someone like TCI or MTE.