Could a 230/400 Volts-50 Hz work proper in U.S.A??

[petronila]

Hello All

I am sending this question to know what do you think about it.

Thanks

Petronila

 

[davidbeach]

Could a 230/400V, 50Hz WHAT work? Without a whole lot more information, the only possible answer is "It depends."

 

[waross]

Yes.
400 Volts x 60Hz/50Hz = 480 Volts.
Current the same.
Running Torque the same
Speed = Original speed x 60/50
Horse power = Original Horse power x 60/50

230 x 60/50 = 276 not good. Use 480 Volts.

If the motor is part of a centrifugal fan or pump, the cube factor at the increased load will result in a 44% overload.
you would have to modify the load. (Different belt ratio, threttle the discharge, reduce the diameter of the impellor, use a VFD and run it at 50 Hz or use torque limiting.)
The motor by itself will work fine. If it's part of a machine, you must use some judgement as to the effect of the higher speed on the machine and the motor loading.
yours

 

[davidbeach]

waross, just for reference, the voltage given in the original post is a wye voltage, 400Y/230V, common in Europe, special order transformer in North America.

 

[petronila]

OK DavidBeach and Waross,

More Information: Twelve Leads, original design : 460 (wye)/230 (Delta)-50 Hz.

 

[davidbeach]

Well, I think waross about covered it. There have also been several other threads on this forum regarding moving motors back and forth between 50 and 60Hz.

 

[jraef]

Twelve Leads, original design : 460 (wye)/230 (Delta)-50 Hz.

That doesn't sound right for a delta Y connection. The original 400/230 would be correct, but 460[÷]1.732 = 266, not 230.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[aolalde]

Almost any induction motor with a satisfactory design for 50 HZ will run at 60 HZ when the V/HZ ratio of the supply is close to a constant.
400V/50HZ = 8
480V/60HZ = 8
That condition imposes a constant flux per pole (Phi).

Phi = Vph / (4.44*F*N*Kw)

Vph = phase voltage
F = frequency in HZ
N = total number of series conductors per phase.
Kw = winding factors.

As the power output increase some mechanical problems could arise, stressed fans, over speeded bearings, increased magnetic circuit losses, excessive windage, high vibration, etc. Again proper evaluation and judgment are required, no golden rule but guidelines.

 

[DickDV]

Take special note of aolalde's answer. It is right on.

The summary is---460V 60Hz on a 400V 50Hz motor is ok but you must not overload it. The 20% increase in speed must be accompanied by a 20% reduction in torque to keep the kw(hp) constant.

Or, in even shorter form, watch out for motor overheating. Otherwise, its ok.

 

[waross]

aolalde
I agree completely.
I have had experience both ways. 50Hz. to 60 Hz. and 60 Hz. to 50 Hz.
A check of the frame size tables will show that most frames are suitable for use at virtually any speed from 1200 to 3600.
Usually there is no problem, but I am aware that when I least expect it, one of the issues you mention may sneak up and bite me in the buttocks.
yours

 

[petronila]

Yes aolalde thanks for the correction,

The Original Design is 400 Volts (Star) and 230 Volts (Delta)- 50 Hz . 12 Leads.

Thanks for the comments

PETRONILA

 

[waross]

The first time that I had to supply a group of motors to a 50Hz. environment, I found that both the price and delivery time exceeded my budjet by an unacceptable amount. I considered re-rating 60 HZ. motors. I did my research, and calculated the results. I then consulted the electrical engineer at a large reputable rewind shop. He confirmed my conclusions. I purchased the 60 HZ. motors and had them sent to the motor shop with a request that they be re-rated for 50 HZ. and new nameplates supplied. The motors were returned with new nameplates that were in agreement with my original calculations. Since then I have done other conversions. One conversion was a small placer mine where all the machinery was purchased second hand in Italy and shipped to North America. No problem with the motors after the conversion to 60 Hz. (A diesel mechanic had stated that the generator would have to be converted to 50 Hz. and that it would lose 1/3rd. of its capacity. It would then be too small and we could buy a new, bigger 50 Hz. generator from his company to run the mine. I fought that bit of urban legend for 5 or 6 weeks. Management finally took a chance that I just may know a bit more about electric motors that a visiting diesel mechanic. The motors were connected at 480 volts, 60 Hz. and ran fine. Everything ran a little faster but all the motor currents were within specs. The generator ran well also.
What I am trying to say is that I have quite a bit of confidence in my statements concerning motor frequency conversion.
Three points.
1> If you check your frame size tables you will find that a frame that is rated at 5 HP at 1750 RPM will be rated 10 HP at 3500 RPM.
2> When you convert from 50 Hz. to 60 Hz. the torque stays the same and the speed increases. The horsepower also increases.
3> Some direct connected loads, particularly centrifugal pumps and fans will over load the motor if they are not modified. This is by far the most common issue with frequency conversion.
I agree with aolalde's statement in this regard;
"As the power output increase some mechanical problems could arise, stressed fans, over speeded bearings, increased magnetic circuit losses, excessive windage, high vibration, etc. Again proper evaluation and judgment are required, no golden rule but guidelines."
I do point out that these problems are rare and when they do occur are almost invariably with the driven machinery rather than in the motor itself.
yours

 

[petronila]

Thanks to all for your repply,

Yes Davidbeach this 50 Hz to 60 Hz cases was covered in the pass, but in this case the problem is not to operate the motor at 480 Volts-60 Hz, Waross covered in detail all math:

" Yes. 400 Volts x 60Hz/50Hz = 480 Volts.Current the same.
Running Torque the same- Speed = Original speed x 60/50
Horse power = Original Horse power x 60/50 (Wye Conected)

230 x 60/50 = 276 not good. Use 480 Volts.(Delta Conected)"

This answer is OK, I was provide more information: Is a 12 Leads Motors.

The problem is operate the motor with 230 Volts-60 Hz(You will need 277 Volts- 60 Hz in order to conserve the volts/Hz Ratio), If you runs the motor with 230 Volts-60 Hz in delta connection the torque will drops to 75% of rated, and with the speed increase the motor will run at 82% of original rating.
With 12 leads you could made 4 possible connections: star , delta, two stars or two deltas.

So for 480 Volts-60 Hz Use a Wye Connection and for 230 Volts- 60 Hz Use Two Wyes connection.The motor will run without problem.

Thanks to all for your help.

Petronila

 

[waross]

Sounds good to me. 400 volts to 460, or 200 volts to 230.
yours

 

[petronila]

Hello Waross,

Thanks for the interest, In the Easa´s technical book, section 3 , 3.11 Connection/Reconnection of Windings we can find an explanation about the three Phase Motors voltage change. The summary is: With some simple calculations and with a table´s help is possible to determine when some motor manufactured with some rated value could work with other voltage making winding reconnection.(External or Internal).In the case of 230 V(Delta) /400 V(Wye)50 Hz Motor, this one can work with 276 V(Delta) / 480 (Wye) 60 Hz, the problem is find the 276 Volts, we ussually have 230 Volts.
For 230 Vots-60 Hz the The procedure is : 1. Find the Ratio of Desired Voltage/ Original Voltage. 2. On below table(THIS IS A PART OF THE TABLE) look for the horizontal line in witch is present the winding connection (In our case is Delta) 3. On this same horizontal line find the number nearest in value to the ratio calculated in 1. 4. Once you find this value look for the equivalent connection in the same vertical column as the voltage ratio number just selected.
Table

0.5 0.33 0.25 0.20 0.17 0.14 0.13 0.58
2Y 0.67 0.50 0.40 0.33 0.29 0.25 1.15
1.5 3Y 0.75 0.60 0.50 0.43 0.38 1.73
2.0 1.33 4Y 0.80 0.67 0.57 0.50 2.31
2.5 1.67 1.25 5Y 0.83 0.71 0.63 2.89
3.0 2.0 1.50 1.20 6Y 0.86 0.75 3.46
3.5 2.33 1.75 1.40 1.17 7Y 0.88 4.04
4.0 2.67 2.0 1.60 1.33 1.14 8Y 4.62
0.87 0.58 0.43 0.35 0.29 0.25 0.22 1 ?
1.73 1.15 0.87 0.69 0.58 0.49 0.43 2.0
2.60 1.73 1.3 1.04 0.87 0.74 0.65 3.0
3.46 2.31 1.73 1.39 1.15 0.99 0.87 4.0

1. Voltage Ratio = 230/276= 0.833, 2. The horizontal line number nine is 1 Delta connection. 3. The nearest value is 0.87 ( is located in the same horizontal line at left side)3. Move upwards and you find 2Y Connection- This is the compatible connection.

For check the compatibility multiply the Number selected in Table (0.87) by Original Voltage(276 )= 240 Volts.

Regards

Petronila