Help with circuit breakers on the line side of the VFD.

[joseph_e2]

You'll probably be ok going one size bigger on the drive, but I'd definitely confirm with the manufacturer just how much oversizing you can do. I've seen problems caused by using a 2HP drive to run a .5HP motor (or something like that).
I would also stick with the manufacturer's recommendation for line side protection. As long as the drive isn't a lot bigger than the motor, it should be smart enough to protect the motor.

 

[Scottryan03]

I would stick with the protector recommended by the manufacturer of the VFD.

We usually oversize our VFDs about 30% H.P. rating. You will just have to adjust the overcurrent/thermal protection of the VFD.

I believe the "Guided Setup" on the ABB drive should walk you through the parameters needed for a basic application.

What is the purpose of oversizing your VFDs?

 

[WhinnieThePooh]

What is the purpose of oversizing your VFDs?

Mostly just for longevity of the drive. In our experience a oversized VFD will have a longer lifespan especially if it is heavily used/abused.

A lot of our customers have mill equipment that runs 12 hours a day at 100% capacity. In a situation like this a oversized drive will run cooler, which (usually) results in longer life.

There may be more reasons to do or not to do this, but we have been doing it this way for 20+ years with no issues.

 

[joseph_e2]

Some AB Drives come with a normal duty and heavy duty rating. We had issues with a drive on a flywheel machine and they recommended oversizing it for the increased DC bus capacity that can absorb more energy. We ended up using a larger brake resistor instead, which solved our issues.

 

[Windrunner]

You'll probably be ok going one size bigger on the drive, but I'd definitely confirm with the manufacturer just how much oversizing you can do. I've seen problems caused by using a 2HP drive to run a .5HP motor (or something like that).
I would also stick with the manufacturer's recommendation for line side protection. As long as the drive isn't a lot bigger than the motor, it should be smart enough to protect the motor.

I will keep this in mind, and I will contact ABB support. Thank you.
I plan to use a 0.5 HP motor, and I have a 1 HP drive. Its recommended motor protector is MS132-6.3, but for example, for a 0.5 HP or 0.75 HP drive, the recommended motor protector is MS132-4 or MS132-2.5. I will also ask them about motor protection.

I also need to check if there is anything said on oversizing in a VFD's manual.

 

[Windrunner]

Hello, sorry for double posting, but I received a reply. Roughly speaking a VFD can be up to 6 times the motor's power.

 

[joseph_e2]

Hello, sorry for double posting, but I received a reply. Roughly speaking a VFD can be up to 6 times the motor's power.

That's good to know from ABB. The ones we had issues with were low-end Allen-Bradley. One did weird things and faulted on something like overload when the motor had a partial ground fault. Their explanation is that the ground fault detection was calibrated for larger motors and that the too-small motor wasn't adequately protected.
That's from memory from years ago, though, so I'm probably forgetting some important details.