VSD(VFD) motor connections Star or Delta

[AustralIan]

To answer your connection question, a motor manufacturer can design a motor to have coils that require whatever voltage they like. It sounds like your motor manufacturer has designed the coils to require 415V across the coils. You can do this by either wiring it in delta at 415V or in star at 700V. Smaller horsepower motors are often designed with 240V coils so you can run them at 240V Delta or 415V Star.

 

[holyhobgoblin]

Sorry for late reply, had to go Papua New Guinea on business.

Basically the equipment is an imported Chinese spray booth which has 2 x VSD's (same models), my last visit before I went away I downloaded the program from the PLC, whilst away I analysed it and found that when changing processes from the HMI, the program would turn off the VSD's for a one program scan.

I have reprogrammed it so the VSD's stay on, this has now stopped the OVER VOLTAGE fault when changing processes.

BUT

Running both VSD's at 50 Hz for 20 minutes - no issues appeared.

I ran both VSD's at 35 Hz for 20 minutes - VSD No.1 tripped out on OVER VOLTAGE after approx 8-10 minutes even tho there was no speed change.

Both VSD's parameter wise are setup completely the same,
parameters for motor info match motor.

I've increased acc/decel times as recommend by the manual

Measured input voltage was 430V, para in VSD's max input voltage set to 440V.

I did run both VDS's with DC VOLTAGE OUTPUT displayed, VSD 1 was reading 591-598 VDC whilst VSD 2 was reading 601-605 VDC. Reading from VSD 1 was constant even to the point of tripping.

I also did swap motors going to the VSD's, and it still tripped on the VSD 1 even tho it was running a different motor.

I am completely baffled to why its trips on OVER VOLTAGE at 35 Hz, even tried at 40 Hz and still trips. With everything i have done i suspect the VSD is at fault.

With the above info can any one shed a light on the problem before i tell the customer he needs a new VSD

Thanx everyone so far for your assistance.

 

[iant]

how are these motors used - is one for extraction and the other for supply air?
I guess they are both driving fans of some description.
Are the two drives fighting eachother?
the DC bus voltage suggests there is a difference - I need more information.
Where are you based

 

[DickDV]

This is almost certainly an input voltage problem with one drive slightly more sensitive than the other. I suspect that neither drive has any input reactance so I would install a 3% line reactor ahead of each drive---one for each one for a total of two.

This accomplishes a couple of good things: First, the reactor will drop some voltage so the DC bus will come down a bit, Second, the reactor will swamp fast and undetectable voltage transients in the power network which can trigger overvoltage faults, Third, the reactor will isolate the two drives from each other so harmonics and diode switching transients cannot cross over and fault the other drive, and Fourth, the reactors will reduce the harmonics radiating back into the power network.

And, they are cheap.

 

[dmargineau]

I think iant pointed you the right direction...
I believe it is a combination of "undersizing" and intake/exhaust air-flow capacity/ratio; the drive will try maintaining the commanded frequency, however since the two fans are dynamically linked, one of them forces the other one to run faster and the drive, trying to "hang back", "pushes" the bus voltage past the maximum bus voltage rating.
The fact that you do not experience any issues running at (and probably above) 50Hz points towards a "size" issue.
Since increasing the HP by 10% is probably not quite feasible, I'd look into trying to run the two fans at slightly different speeds since it's obviously an air flow issue; try slowing down the VDS which does not trip in small increments until (hopefully) the issue goes away.

P.S. Sorry DickDV, you are bringing up a valid point too. I will never install a VFD without at least a Line Reactor...However, Made in China has it's own "qualities"...

 

[iant]

I agree with the Idea of fitting reactors - these are compulsary here.
But, as usual companies are buying the 'Cheap' equipment from China.
usually totally wrong for the situation.
I wonder how the Spray booth is heated

 

[maxketcham]

IF you look at the buss voltages on drive 1 and drive 2 there is something that stuck out to me. The buss voltage differences were 2X greater on drive 1 than drive 2. To me this means that motor 1 is being either over-driven (the motor is running faster than the drive is telling it to run)or you have bad bus capacitors. I would try drive 1 by itself without drive 2 running and see what happens.

 

[holyhobgoblin]

Well folks, after all the hair pulling, banging my head against the wall and phone calls to a Delta Rep, it appears the fault comes down to a cheap nasty Chinese relay.

The relay is driven by the PLC to make the digital input on the VSD to start it, the relay simply make/breaks after a period of time dropping out the VSD then bring it back online.

Some times looking to hard can be the problem.

Thanks guys for your input, refreshed some old knowledge and learnt some new stuff.

BTW. After explaining everything to the Delta Rep he came to the same conclusion as me that the drive was faulty, goes to sure rep don't always know everything.

Cheers

 

[iant]

'Cheap' equipment from China
like I said
we have found Panasonic relay bases faulty also
so beware