12-17-2014, 10:55 AM
I'm a big fan of using VFD's for getting 3PH power for home use.
Having said that, I get a bad feeling about trying to power a 5 hp motor from a 3 hp VFD.
During set up, you enter things like rated RPM, HP, and "full load amps" into the drive parameters. The drive later uses these parameters to control the motor start-up, to control torque boost at lower than rated speeds; to decide when to shut down on high load current, etc.
With a 5 HP motor, you will have to "spoof" the 3 HP drive into thinking it is running a 3 HP motor. I am afraid that many of the "preset" parameters will then not be valid. The VFD is going to see more electrical reactance than it is expecting. You still may be able to make it work, but you may have to do a lot of tuning on drive parameters that you would otherwise not have to mess with. Most of these drives have dozens of adjustable parameters - and the tuning of one can often affect the tuning of another.
If you are careful in setting up the drive - I don't think you will hurt it by experimenting with the 5HP motor. If the 5 HP motor proves unworkable, you can then invest in a 3 HP (or smaller) motor. In any case, get a Korean or Japanese drive with good documentation supporting it. You probably have to spend $200 - $300 for such a drive. Personally, I like Westinghouse TECO EV "Microdrive" series (but not the FM series which is an older drive). Others have mentioned other good drives.
Another note: even with a VFD, the capability of a stepped pulley system is a good thing. VFDs and motors like to run near their rated speed and down to perhaps 50% (maybe as low as 30% rated speed if you are careful with motor cooling). The stepped pulley system allows you to turn large diameter bowls as well as small diameter spindles and still keep the motor at a reasonable speed with good torque.
Terry S.
Having said that, I get a bad feeling about trying to power a 5 hp motor from a 3 hp VFD.
During set up, you enter things like rated RPM, HP, and "full load amps" into the drive parameters. The drive later uses these parameters to control the motor start-up, to control torque boost at lower than rated speeds; to decide when to shut down on high load current, etc.
With a 5 HP motor, you will have to "spoof" the 3 HP drive into thinking it is running a 3 HP motor. I am afraid that many of the "preset" parameters will then not be valid. The VFD is going to see more electrical reactance than it is expecting. You still may be able to make it work, but you may have to do a lot of tuning on drive parameters that you would otherwise not have to mess with. Most of these drives have dozens of adjustable parameters - and the tuning of one can often affect the tuning of another.
If you are careful in setting up the drive - I don't think you will hurt it by experimenting with the 5HP motor. If the 5 HP motor proves unworkable, you can then invest in a 3 HP (or smaller) motor. In any case, get a Korean or Japanese drive with good documentation supporting it. You probably have to spend $200 - $300 for such a drive. Personally, I like Westinghouse TECO EV "Microdrive" series (but not the FM series which is an older drive). Others have mentioned other good drives.
Another note: even with a VFD, the capability of a stepped pulley system is a good thing. VFDs and motors like to run near their rated speed and down to perhaps 50% (maybe as low as 30% rated speed if you are careful with motor cooling). The stepped pulley system allows you to turn large diameter bowls as well as small diameter spindles and still keep the motor at a reasonable speed with good torque.
Terry S.