Can I use a 5hp vfd on a 2hp or 3hp motor?

[Gregory of Sherwood Forest]

Title pretty much sums it up. I can get a practically free teco 7300 5hp vfd, but want to use it on either a 2hp or 3hp motor.

Any issues with that?

Thanks in advance.

[TDKPE]

What's the input? Single-phase, or three-phase? Not that it matters, but if it's 3-phase, then it will only be good for 2-3 hp output if running it on single-phase anyway. But it should work fine with a smaller motor than it's rated for.

[Gregory of Sherwood Forest]

3 phase. Another lathe.

[TDKPE]

Here's the manual.  

http://download.factorymation.com/acdriv...df?r=false

It's a sensorless vector drive, but it looks like it can be configured for V/Hz mode, like the less expensive drives, where output voltage is reduced as the output frequency is decreased below 60Hz to maintain motor torque capability.  Vector drives actually get feedback from the rotor, either with an encoder (hoists, elevators) or just by looking at what's being reflected back through the motor leads (sensorless), and adjusting the voltage and frequency to maintain the commanded rotor speed under varying loads. 

I don't know if it will play well with a smaller motor in vector mode, but it should be fine in V/Hz mode.  What's not clear is whether or not you can power it with single-phase power at reduced output power like you can with many less expensive drives, even though they're not marketed that way.  It may detect the missing input phase, or it may not - I don't see anything in the specs stating that it monitors input phase voltage or lack thereof, so it's possible it will work fine.

You could always call Factorymation and ask them, but if the drive is cheap, you're not risking much giving it a try.  Sorry for the flabby answer, but I only work with little V/Hz drives at home, and larger vector drives at work (hoists mainly, typically 30 hp and up), and don't know much about sensorless vector drives like this one, especially with an input phase missing.

[Gregory of Sherwood Forest]

I just realized that I may have given the wrong response. I have 220v single phase in the shop. I want to use the vfd to run a 5hp 3ph motor.

[TDKPE]

I just realized that I may have given the wrong response. I have 220v single phase in the shop. I want to use the vfd to run a 5hp 3ph motor.

In that case, it's not going to work.  It's a 3-phase input, and running it on single-phase will only get you 2-3 hp, if it works at all.  But not 5 hp worth of output.

[Gregory of Sherwood Forest]

Crap. I mistated it again.
The TECO VFD is rated for up to 5hp
The motor is 3hp, 3 phase
My shop has 220v single phase.

There.

[Tapper]

Crap. I mistated it again.
The TECO VFD is rated for up to 5hp
The motor is 3hp, 3 phase
My shop has 220v single phase.

There.

No expert here but if the VFD is rated for up to 5 HP and the motor is only 3 HP, you should be good to go. 220v in, 3 phase out, correct? That's one of the things VFD's do best.

Doug

[EricU]

I suspect it will work.  Most manufacturers would say though.  There is a note that if the motor speed is not constant you should add a reactor to the unused power input.  

I really don't think they would spend the money to add circuitry to check to see if there is an input phase missing. It's just not that big of a deal. Manufacturers will often say to derate the drive if you use single phase.

I assume you already have it. If not, I would buy something else

[fredhargis]

Tom will be back with the nitty gritty, but I run my 1.5 HP lathe on a 5HP (GE Industrial) VFD.