Swap motor or single to 3 phase VFD?

Status
Not open for further replies.
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Occupation
Electrician
I have a five horsepower wood shaper that needs to run off single phase. I'm torn between swapping the motor and using a VFD. Cost each way seems about the same, somewhere around $600, with the VFD probably being a little cheaper. Swapping the motor would be fairly straightforward, nothing funky or difficult about it. Variable speed is not needed and would not be used, it would just be for phase conversion. Any other considerations on maybe not thinking of?
 
electrofelon said:
I have a five horsepower wood shaper that needs to run off single phase. I'm torn between swapping the motor and using a VFD. Cost each way seems about the same, somewhere around $600, with the VFD probably being a little cheaper. Swapping the motor would be fairly straightforward, nothing funky or difficult about it. Variable speed is not needed and would not be used, it would just be for phase conversion. Any other considerations on maybe not thinking of?
Click to expand...
$600 seems too low for the VFD. At 5HP, are you aware that most require a 65% de-rate when you have a single phase supply? That means you need a VFD that is rated 15HP in many cases (10HP in a few cases if the drive has a DC bus choke). You can’t just use a 5HP VFD.

Be careful. If you are planning on buying one of the off-brand Chinese junk drives on-line, there is a notorious one (sold under several names) that lies about being rated for 5HP @ single phase input in their ad page. You don’t find out until it arrives and trips out, then you read the manual and it tells you that it needed to be de-rated.
 
@ Jraef, I would like to try spinning up a 30HP 230V 3Φ unloaded motor, to start as a RPC idler. What size VFD do you think I could get away with using a quality brand, while supplying it with 1Φ 230V. Would be just for momentarily bringing it up to speed, instead of capacitor or pony starting. I'm not too concerned about the ramp time, more interested about capability and durability. Controls would be in place to isolate the drive output before powering up the RPC source. Any suggestions?
 
Jraef said:
$600 seems too low for the VFD. At 5HP, are you aware that most require a 65% de-rate when you have a single phase supply? That means you need a VFD that is rated 15HP in many cases (10HP in a few cases if the drive has a DC bus choke). You can’t just use a 5HP VFD.

Be careful. If you are planning on buying one of the off-brand Chinese junk drives on-line, there is a notorious one (sold under several names) that lies about being rated for 5HP @ single phase input in their ad page. You don’t find out until it arrives and trips out, then you read the manual and it tells you that it needed to be de-rated.
Click to expand...
Yes I made certain to size at single phase input. There are a bunch out there that are priced from $525-$725.
 
Agree w/ Tom. For a basic start/stop setup like your shaper, you will need to input a small handful of motor parameters, all of which you will get from the motor nameplate. Then also input how fast you want it to run, and what the accel and decel ramps are (meaning how quickly you want it to start and stop).

Dare I say it, it could even be fun!! But I am an engineer. ;)


Another minor consideration in favor of the VFD... if the shaper ever goes south for whatever reason, it's easy to save and repurpose a VFD - or even sell it. It's often a bit harder to repurpose a motor. VFDs are, by their nature, quite flexible.
 
MD Automation said:
Agree w/ Tom. For a basic start/stop setup like your shaper, you will need to input a small handful of motor parameters, all of which you will get from the motor nameplate. Then also input how fast you want it to run, and what the accel and decel ramps are (meaning how quickly you want it to start and stop).

Dare I say it, it could even be fun!! But I am an engineer. ;)
Click to expand...
Yeah It might be kind of fun! So actually this is for a friend of mine, so I'm just giving him some advice he will probably do most of the work, other than the main electrical connections.
 
MD Automation said:
Agree w/ Tom. For a basic start/stop setup like your shaper, you will need to input a small handful of motor parameters, all of which you will get from the motor nameplate. Then also input how fast you want it to run, and what the accel and decel ramps are (meaning how quickly you want it to start and stop).

Dare I say it, it could even be fun!! But I am an engineer. ;)


Another minor consideration in favor of the VFD... if the shaper ever goes south for whatever reason, it's easy to save and repurpose a VFD - or even sell it. It's often a bit harder to repurpose a motor. VFDs are, by their nature, quite flexible.
Click to expand...
It's not any harder than setting up a program able thermostat
 
Status
Not open for further replies.
Top