VFD Question

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Colombo7

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Hello all,

First of all, I am not an Electrical engineer. I am a Mechanical and a Software engineer, that understand and has only been working with low voltage controls (as in 24VDC and +/-15 VDC instruments, but a complete dummy when it comes to 3 phase AC. I have asked this question in many other forums and I am still at a loss as to all the various explanations that I have gotten.

Just one scenario that I would like to get clarified.

Facilities Power:

400VAC, 3 Phase, 60Hz 4-Wire Supply (Yes, 60Hz and not 50Hz). A FACTORY IN THE US.

Equipment:

Motor specified as; 230/400V Delta/Wye at 50Hz.

My Question;

Using a VFD with an input voltage of 3 phase 400VAC at 60 Hz, Can I control the motor above in a Delta configuration where motor voltage is clamped at 230VAC and at 50Hz, while VFD input is at 400VAC 60Hz?

Thanks.
 
Per that exact scenario, and ASSuming that the motor is a 400/230V 50Hz motor, then yes. But from recollection of your other postings, your motor was stated as being 240/480V, which made a difference. Details matter.

So if this is now confirmed as a 230/400V 50Hz motor, you can program the VFD to provide 230V 50Hz from a 400V 60Hz source, no problem for the drive. But it may be a problem for the motor windings because the pulses that make up the Pulse Width Modulated (PWM) output of the VFD will be around 565VDC based on the 400VAC input, instead of the 330VDC that the windings would expect from a 230VAC source. That can cause long term damage to the winding insulation. Fortunately you can ALSO by the way tell the VFD to put out 400V 50Hz too and just use the motor as designed. A VFD converts the AC to DC no matter what and recreates the output as whatever you tell it to do, so it doesn’t care if the input is 50Hz or 60Hz. It just can’t put out MORE voltage than it was given, so with a 400V input you are limited to a 400V output at any frequency.

The problem with how you asked and presented the issue before was that you said you wanted to power a 480V motor from a 400V supply. That would not have worked.
 
First, was that a typo? Most American factories are supplied with 480 volts.

Yes, this can be done.

One of the many things a VFD does is to maintain a constant* volts per Hertz ratio -- when the frequency is changed to change the motor speed, the voltage is changed proportionally.

If you have 480volts/60Hz available, it would be best to wire the motor in the Y configuration. The efficiency will be higher, the current will be lower and your electrician will need to buy and install less copper to hook it up.
A motor specified for 400volts/50Hz is expecting 8 volts/Hz, same as 480volts/60Hz. It should run just fine on either supply. It will run 20% faster on 60Hz than on 50Hz.

If you actually have only 400volts/60 Hz, you can still run this motor in Y configuration with a VFD, but you may need to limit it to 50Hz and you may need to reset the VFD's undervoltage trip.

The only reason I can imagine for running it in the Δ configuration is if you need to run it significantly faster than the nameplate speed. If you do, you will need to reconfigure the VFD for 4.6 volts per Hertz.

A photograph of the nameplates of your motor and VFD would be most helpful.
 
I am in general agreement with what has been said above.

1) The VFD converts input AC to DC, and then uses that DC to produce arbitrary frequency and voltage AC. So you will be able to run any reasonable frequency motor up to a maximum voltage that depends on the internal DC voltage of the VFD.

2) The output of the VFD is not a true sine wave AC. Rather the output consists of high frequency pulses (1-10kHz) that are at the voltage of the DC rail. These pulses can put significant additional stress on the motor insulation. These pulses are modulated to cause approximately sinusoidal AC current to flow through the motor.

3) A very few (and more expensive) line regenerative VFD units have input rectification that boosts the DC rail voltage to above that seen in normal VFDs that use simple 6 step rectifiers. These units could produce an output voltage greater than the input.

4) If, given the combination of input voltage and motor ratings, you cannot get sufficient voltage to run the motor at _rated voltage_ and _rated frequency_, you can still run the motor at reduced speed. This means running the motor at reduced frequency, which also requires reduced voltage.

-Jon
 
Jraef said:
The problem with how you asked and presented the issue before was that you said you wanted to power a 480V motor from a 400V supply. That would not have worked.
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We had a VSD project quite a few years back for a water pumping station in rural Yorkshire.There were four 760 kW variable speed drives so not little tiddlers. The supply voltage to the pumping station was 3.3kV and the motors were 690V. At that point in the dim and distant past the highest output voltage available from a standard VFD was in the 400V range.

So we had a step down input transformer and a step up auto on the output. So yes, you can make it work.
Somewhat of an aside, because of the remote location, harmonics were an issue to be considered so we went 12-pulse and I designed the 3.3kV harmonic filters. A one-shot deal. You can go over the calcs a dozen times and still get sweaty palms when it comes to commissioning/verifying performance.

Mods, forgive my digression.
 
Yes, you CAN run a 460V motor from a 400V supply but it requires more hardware, ie a transformer on the output (or an Active Front End drive, which is roughly 2x the cost).

There are numerous companies in the Semiconductor industry who have “Fabs” (factories that make wafers) in countries all over the world. So what they do is design everything to be the same, ie 400V so that every Fab is exactly the same wherever they go (Intel has a requirement referred to as “Copy Exact” that applies to every tiny little detail, right down to the plating on assembly screws, many of their competitors have adopted the same philosophy). Here in North America the Fab builders buy custom service transformers for the production areas.
 
Besoeker3 said:
... You can go over the calcs a dozen times and still get sweaty palms when it comes to commissioning/verifying performance. ...
Click to expand...
Been there. Accurate calculations aren't sufficient if you overlooked something or made an incorrect assumption, and I always worry until it's been hiccup-free for a year.
 
drcampbell said:
Been there. Accurate calculations aren't sufficient if you overlooked something or made an incorrect assumption, and I always worry until it's been hiccup-free for a year.
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Then it wouldn't be an accurate calculation.
 
Jraef said:
There are numerous companies in the Semiconductor industry who have “Fabs” (factories that make wafers) in countries all over the world. So what they do is design everything to be the same, ie 400V so that every Fab is exactly the same wherever they go.
Click to expand...


Check Infineon.
 
I would like to add an additional warning on this. If the vfd has a bypass assembly, that will cause some big issues. A bypass assembly is an across the line starter that completely bypasses the vfd rectification.

Basically, you have to make sure that you don't have a bypass assembly on the vfd. Hopefully this isn't for critical equipment where a failure of the vfd itself will be a big problem.
 
Thank you all for your help.

400VAC, 3 Phase, 60Hz 4-Wire Supply (Yes, 60Hz and not 50Hz). A FACTORY IN THE US.

Equipment:

Motor specified as; 230/400V Delta/Wye at 50Hz.
Click to expand...

That was NOT A TYPO.

It is a NEW factory in the US that is less than a year old. They have three older factories in the US that is supplied with 480VAC 60Hz. All of their next generation factories around the world are 400VAC 50Hz. They were not able to replicate the 50Hz in the new US factory. I am guessing due to cost factors involved.

A new question on the same subject....Single Phase vs. 3-Phase input power in to the VFD

It is my understanding that lower voltage printed on the motor label refers to a single phase supply voltage. At least according to some documentation I read that was published by Baldor Motor Co. It sates for 230VAC use, single phase is used to power up the motor.

Was that statement accurate?


Q1. Does this mean Delta Configuration is for single phase use and Wye configuration is for 3-Phase connection?

Q2. How can I wire the incoming power (As a single phase) to the VFD? Does L2, L3, Connections get tied to the Neutral at the VFD input?

Thx.
 
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Your motor is a 3 phase motor, either low voltage (delta connection) or high voltage (wye).

I don't know of any motor that is switched between single and 3 phase, but I suppose stranger things are possible.

If you have 3 phase available, you would supply all 3 phases to the VFD, even if for some reason you were using a single phase output. VFDs are frequently used to convert single phase to 3 phase, but not the other direction.

-Jon
 
I agree, you are misinterpreting something in the motor as referring to single phase as the 230V input if it is a 3 phase motor. That makes zero sense. Can you post a photo of the motor data plate or direct us to what you are reading?
 
What I am also confused about is in column 2, it indicates that both 230 and 400 VAC can be connected as single phase. How is 400VAC single phase possible if Grid Supply is 400VAC 3-Phase?

Thx.
 
Colombo7 said:
What I am also confused about is in column 2, it indicates that both 230 and 400 VAC can be connected as single phase. How is 400VAC single phase possible if Grid Supply is 400VAC 3-Phase?

Thx.
Click to expand...

It’s simply saying that a 400V single phase load (if anything like this exists!) can be connected across any 2 of the phases.
 
retirede said:
It’s simply saying that a 400V single phase load (if anything like this exists!) can be connected across any 2 of the phases.
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They certainly do exist. Over almost 50 years, our control transformers were almost all 400V in, 110V out.#
 
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