Any VFD gurus' out there?

[ngwagwa]

Not pecifically CNC but I thought someone on here may be able to help. I have obtained a Clarkson cutter grinder which came with a dust extractor, both being 3 phase and I have been looking at the possibility of running both off the same VFD with frequency fixed at 50Hz. Searching the web leads me to think this is possible but I am looking for the settings for the VFD. I have HuanYang 2.2Kw VFD hanging around so would like to try and use that.

Has anyone on here done anything similar or have any tips?

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[John11668]

Seems to be discouraged but I run my lathe and coolant pump from a single VFD.
In parallel but with an isolating switch for the coolant if not needed . 2..2 K sounds a bit overboard for a Clarkson though.

[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/articles/2011-1/vfds-can-control-multiple-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).

[depronman]

I think separate vfd would be best if you want that sort of flexibility
I bought a Siemens vfd from eBay for £30 which would be suitable for either motor
Really good but if kit new in a box. Old stock but never used

Paul


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[Doddy]

Just a point - the Huanyang manual does say NOT to include a contactor between the output terminals and the load, unless you can guarantee no output from the VFD when the contactor is switched. So that adds complexity if you're looking to have independently switched motors.

HP to kW?, just think of 1Hp as 745W (or wet-finger 750W)

Personally, I'd get a cheap VFD for the extraction system.

edit: corrected HP/kW scaling

[John11668]

In my case the coolant motor is a fraction of the Lathe motor , and the VFD started via the lathe drum switch.
I worked on the basis that adding a further load when the lathe motor was already running was not a lot different to starting a decent cut and I have the VFD set for torque boost to take that on board .
I dont know how it would handle two motors of equal size but certainly sounds like your application would be better handled by separate VFDs.
The fact that you may wish to use the extractor ICW another machine would also make me choose that route.

[ngwagwa]

Right - going to use 2 VFDs so I can use the extractor on it's own.

Doddys point re wiring VFD direct to motor tken onboard.

Has anyone a starting point for setting the VFD variables?