Any VFD gurus' out there?

[Doddy]

Overboard?, perhaps. I was perhaps a little concerned with starting two large-ish motors in parallel off a single VFD - gonna be a chunk of amps there. But overspending the VFD may well help a bunch there. The motor plates add up to about 1.5HP which is around 1100W, so a 2.2kW VFD is not stupidly large.

[depronman]

Overboard?, perhaps. I was perhaps a little concerned with starting two large-ish motors in parallel off a single VFD - gonna be a chunk of amps there. But overspending the VFD may well help a bunch there. The motor plates add up to about 1.5HP which is around 1100W, so a 2.2kW VFD is not stupidly large.

I totally agree a larger vfd as an easier life if it’s only running at say 30to50% max capacity. And let’s face it the Chinese do dream about on there specs
I would arrange it so that both motors are not started at the same time as on start up the amps draw is a lot more than when in run mode
Maybe 2 or 3 seconds before motor 2 is started

Paul


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[ngwagwa]

Overboard?, perhaps. I was perhaps a little concerned with starting two large-ish motors in parallel off a single VFD - gonna be a chunk of amps there. But overspending the VFD may well help a bunch there. The motor plates add up to about 1.5HP which is around 1100W, so a 2.2kW VFD is not stupidly large.

Hi (again) from what I have read (and possibly misunderstood) I have two options:
a) start both the motors at the same time in which case the VFD controls the ramp up speed of the motors so the VFD can be sized by adding the power requirements of the two motors.
b) If both motors aren't started at the same time then the VFD must be sized by adding the FLA of the motor started first to the locked rotor amps of the second motor.
Thsi is where it all becomes hard for me to follow - why do they mix HP and Kw confuses me.

https://www.automation.com/en-us/art...ultiple-motors

At this point I am leaning towards wanting to turn on the dust extractor independantly so I can use it with another machine as well as the grinder in which case I think it best to either get another VFD for it or convert it to 240V unless I put a switch in that would make the dust extractor become the primary motor instead of the grinder. Both motors being the same size helps here (I think).