# Delta vs Wye, Voltage / Frequency selection



## vinister (Apr 11, 2012)

I have the following equipment:


HPS 20kVA drive isolation transformer with 600V YNd1 (-30°) secondary (TE3A0020BPM)
Eaton PowerXL DG1 enclosed drive, 600V input, (DG1-35022FB-C21C)
Weg W22 15kW motor


























The available connection voltages on the motor nameplate are as follows:

380 Δ / 660 Y (50hz)
400 Δ / 690 Y (50hz)
415 Δ (50hz)
460 Δ (60hz)

I'd be grateful for some insights about the motor connections. I am assuming 600V Y connection will be fine with the VFD controlling the frequency. I specc'd the drive with a 0-100% speed control knob on the panel which provides the 0-10V control to the VFD. 

Anyone see any obvious deal-breakers or incompatibilities here?


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## just the cowboy (Sep 4, 2013)

Since your drive will only put out 600 volts and the motor is rated at 690 volts there will be a volts to hertz issue.
you need the drive to put out 13.5 volts per Hz. That comes out to be 44 hz at 600 volts.
Your motor will run slower but this keeps the motor/drive ratio correct.
The drive should have a setting to allow this change, sometimes it is one setting sometimes changing the motor data will fool the drive depends on the drive.
@JRaef will chime in.

Cowboy


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## CMP (Oct 30, 2019)

I would think that you wire the motor for 460V 60HZ delta , and program the drive for a 460V 60Hz 15KV motor 1775 RPM


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## just the cowboy (Sep 4, 2013)

Yep you could do it that way but i always tried to stay away from that because if someone changes a drive or setting in the drive you could overvoltage the motor. 
It is a WEG motor. My bet is the machine was designed for 50hz. Even though the motor is rated at 480 volts the lose hp at the 480 end, and machines I had had trouble with that.
I had blowers that we ordered at 480V 60Hz. All they did was change the motor but not the blower size. We had troubles till we installed VFD's and ran them at 380/50Hz.


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## CMP (Oct 30, 2019)

I get your point. In the case of blowers and pumps increasing the speed increases the load.
I assumed that he's in 60Hz land so all of the other voltages are listed for 50HZ
In your case of fans the motor drive pulley should have been changed with the motor, to match the new motor to the load, to prevent overload. Just another way to skin the cat, without the VFD expense.

In his case. He never stated what the load is, so we can only speculate.

As far as people changing things afterwards, you cant always control what people do after you leave a job. Several times I've had maintenance people modify things even before the inspection was complete. Some things are just outside your control.


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## vinister (Apr 11, 2012)

This is an awesome discussion and great advice, thanks! This is a fan motor, and I have complete control, nobody is going to change any settings. And yes, it's European, designed for 50hz. But it seems like running it at 460V delta 60hz is a good start. My only concern is the nameplate says 24.7A, are we maybe too close with the 22/27A rating for the output of the drive? I entrusted the Eaton engineers to spec out the drive, after sending them the motor specs, have they specc'd the correct drive?

Why does the motor require less voltage ran in a Delta configuration than it does in a Wye configuration, yet spins at a higher RPM?


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## micromind (Aug 11, 2007)

The speed of the motor is based on HZ. 

The Y voltage will be 1.73 X the ∆ voltage. 

If it were me, I'd connect the motor ∆ and program the VFD for 400 max volts and 50 max HZ. 

On the lower right of the nameplate, it states that operating at 460 Volts and 60 HZ, the service factor is 1.25. What it doesn't state is that when operating with a VFD, the S. F. is 1.00

If it's a fan designed for 50 HZ and it's run at 60 HZ, it'll almost certainly be overloaded. 

If you want to get the maximum possible out of it, adjust the max HZ up until the current is about 28 or so. You'll need to adjust the max voltage a bit higher too.


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## gpop (May 14, 2018)

micromind said:


> The speed of the motor is based on HZ.
> 
> The Y voltage will be 1.73 X the ∆ voltage.
> 
> ...



We had a large fan that was close to its max rated speed at 60 hertz. The told me to set the drive to 62 hertz.

It lasted 30 seconds before it ripped to pieces. 
I would look at the fan, pulleys etc then deiced on the speed required and go from there.


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## vinister (Apr 11, 2012)

micromind said:


> The speed of the motor is based on HZ.
> 
> The Y voltage will be 1.73 X the ∆ voltage.
> 
> ...


Ok, let me try to see if I understand what you're saying. Since the fan + motor assembly was designed to be used in Europe, there is an assumption that it will be run at 50Hz, and thus the mechanical assembly of the fan itself would have been designed for x rotation speed that 50hz will provide. The motor is capable of running at 60hz, and will turn faster, potentially faster than the fan itself can handle. So you are recommending staying at 50hz for that reason. Perhaps I could run it at 60hz if I change the pulley to reduce the speed, but why bother when I can do that digitally, right?

So I should program the VFD for max 50hz, max 400V, and run it. Then to get a bit more out of it, I can bump the max hz and max V up a bit, so long as I don't exceed the 28A to the windings. 


How does the VFD extrapolate what voltage/frequency combination it needs to provide at reduced speeds?

To give further context here, this is a fan for a vehicle dyno. There is a 0-100% knob on the front of the enclosed drive, along with a manual/auto selector switch. When set to auto, a 0-10V signal from the dyno takes over the fan speed, so that the speed ramps up and down with the speed of the car, to help simulate a real road. I'll use an anemometer to try to match the wind speed in front of the car to the speedo.


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## varmit (Apr 19, 2009)

i would think that your most simple method would be to wire the motor for 480 volts and limit the VFD output to 50 hertz. 
You do not want to run a 50 hertz fan or pump on 60 hertz. The current will be more and the motor life will be less.

This would:
Keep the volts/hertz ratio correct.
This will keep the fan speed at the correct max speed.
The FLA, of the motor, would be around 21 amps at 50 hertz. This would be due to the fan running at about 300 RPM less than the 480 volts at 60 hertz speed. 
Set up will be more easy.


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## micromind (Aug 11, 2007)

vinister said:


> Ok, let me try to see if I understand what you're saying. Since the fan + motor assembly was designed to be used in Europe, there is an assumption that it will be run at 50Hz, and thus the mechanical assembly of the fan itself would have been designed for x rotation speed that 50hz will provide. The motor is capable of running at 60hz, and will turn faster, potentially faster than the fan itself can handle. So you are recommending staying at 50hz for that reason. Perhaps I could run it at 60hz if I change the pulley to reduce the speed, but why bother when I can do that digitally, right?
> 
> So I should program the VFD for max 50hz, max 400V, and run it. Then to get a bit more out of it, I can bump the max hz and max V up a bit, so long as I don't exceed the 28A to the windings.
> 
> ...


You've got it!

Plus, the HP required to drive a centrifugal fan (or pump) will increase dramatically with increased speed. 

The VFD will automatically vary the voltage when the HZ is changed. For example, lets say we had a motor that ran at 1800 RPM at 60HZ and 460 volts. If we reduce the HZ to 30, the motor will now run at 900 RPM and the VFD will provide about 230 volts.


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## paulengr (Oct 8, 2017)

vinister said:


> Ok, let me try to see if I understand what you're saying. Since the fan + motor assembly was designed to be used in Europe, there is an assumption that it will be run at 50Hz, and thus the mechanical assembly of the fan itself would have been designed for x rotation speed that 50hz will provide. The motor is capable of running at 60hz, and will turn faster, potentially faster than the fan itself can handle. So you are recommending staying at 50hz for that reason. Perhaps I could run it at 60hz if I change the pulley to reduce the speed, but why bother when I can do that digitally, right?
> 
> So I should program the VFD for max 50hz, max 400V, and run it. Then to get a bit more out of it, I can bump the max hz and max V up a bit, so long as I don't exceed the 28A to the windings.
> 
> ...


Roughly speaking you need to keep the Vilts/Gz ratio constant in the VFD. Another way to look at it is Power=torque x RPM x (conversion factor for units). And there are two currents in the motor. One is flux. It is roughly constant and since it does NO work it is almost exactly 90 degrees lagging. The second is torque where the torque output is equal to the torque current times a constant. At max RPM with constant torque and HP flux is about 10-15%. So at that point if I cut my frequency in half I need to reduce the power accordingly so I cut voltage in half, too. So approximately speaking Volts and Hz is a constant except at low Hz where flux dominates and we have to maintain some voltage even as we reduce frequency further, at around 15% if maximum speed.

Also look up fan affinity curves. It should be obvious why small increases in speed at the upper end produce exponential power increases.

The rest of what you are seeing is a “global” name plate where someone is giving you rerated values depending on input voltage and frequency. Ultimately going back to what I said...Power = torque x frequency which is a thermal limit. So if you raise frequency consequently you must decrease voltage or connect it to see decreased voltage with say parallel coils. Multiple possible combinations here for maximum performance but including running above name plate frequency while maintaining maximum voltage.

Also the drive might be capable of higher voltages but be careful. 700 V is generally the limit on the IGBTs so maximum output is usually 690 V on low voltage IGBTs and is sort of an industry standard.


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## just the cowboy (Sep 4, 2013)

CMP said:


> In your case of fans the motor drive pulley should have been changed with the motor, to match the new motor to the load, to prevent overload. Just another way to skin the cat, without the VFD expense.


Direct drive blower


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