Oversized VFD

[Saturn_Europa]

I'm removing a 3hp motor and fan and installing a new 5 hp motor and fan.

I've got a 10 hp vfd as a spare I'm going to use. are there any issues with over sizing a vfd?

 

[winnie]

In general, the VFD itself is fine oversized as long as the correct motor parameters are programmed. A 2X oversize is not a problem for drive or motor.

The issue is the size of the circuit feeding the VFD. See https://forums.mikeholt.com/threads...ith-soft-starters-and-vfds.89936/post-1439880

You would end up installing larger supply circuit than you really need because of the input current rating of the VFD. I think that as a practical matter in your case the circuits might be small enough to not make a big difference either way.

-Jon

 

[Saturn_Europa]

In general, the VFD itself is fine oversized as long as the correct motor parameters are programmed. A 2X oversize is not a problem for drive or motor.

The issue is the size of the circuit feeding the VFD. See https://forums.mikeholt.com/threads...ith-soft-starters-and-vfds.89936/post-1439880

You would end up installing larger supply circuit than you really need because of the input current rating of the VFD. I think that as a practical matter in your case the circuits might be small enough to not make a big difference either way.

-Jon

Thank you, Jon! I'm up sizing the supply circuit anyway. it was run with 16 awg

appreciate ur input

 

[Jraef]

Most VFDs have a minimum motor size that you can hook up to it, because the current sensors inside have an accuracy factor below a certain range. For most VFDs that minimum is going to be 50% of the VFD rated output, so you should be fine.

 

[paulengr]

A motor can develop up to 250-300% of nameplate torque at pull out. The “name plate” horsepower rating on a VFD only allows for 10% extra current (torque) for 60 seconds when sold as “standard duty” or “variable torque” which is the number you see often used on model numbers. You may also see a “constant torque” or “heavy duty” rating which is 135% of name plate for 60 seconds. This covers most applications. Some like rock crusher screens need double the “horsepower” rating and even then may need a brake resistor too. These loads drive the software algorithms crazy.

So you have to know your load to “size” a VFD.