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iftikhar129
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Join Date: Dec 2011
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50Hz vs 60Hz

02/20/2012 12:36 AM

i have a machine rated 480v, 60Hz. as the utility supply in my area is 400V(3P), 50 Hz.

i am planning to run it on 480V, & 50Hz by steping-up the transformer voltage.

please comment on my idea.

Thanks in advance.
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Tornado
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#1

Re: 50Hz vs 60Hz

02/20/2012 12:55 AM

Probably not desirable. Better proportions would be at 400V, 50Hz, and 5/6 of the 480/60 HP or KW rating.

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SolarEagle
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#2

Re: 50Hz vs 60Hz

02/20/2012 1:26 AM

If you step up voltage and not frequency you will lose about 20% rated RPM...You can pair your transformer with a VFD to meet requirements...unless of course you want to drop the RPM...

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dvmdsc
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#3
In reply to #2

Re: 50Hz vs 60Hz

02/20/2012 1:59 AM

And probably drop also the motor, into the garbage or in the re-winding shop, after it burned down. Will get hot as fire.

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arifkunnath
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#5
In reply to #3

Re: 50Hz vs 60Hz

02/20/2012 4:56 AM

Is there a chance of burning the motor even with the use of VFD in this case ?
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dvmdsc
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#9
In reply to #5

Re: 50Hz vs 60Hz

02/20/2012 9:25 PM

As long as you keep your supplying VFD in the 60 Hz frequency range, your 480 Volts will be OK. This way you create the design and working condition for the motor.

The other scenario that TORNADO suggested is also acceptable.

Some VFD's can also step up the voltage for you, so that the transformer isn't needed.

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Crabtree
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#4

Re: 50Hz vs 60Hz

02/20/2012 3:50 AM

Well, if your "machine" were a synchronous clock, it would run slow. What sort of machine is this, Captain?

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iftikhar129
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Join Date: Dec 2011
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#6
In reply to #4

Re: 50Hz vs 60Hz

02/20/2012 6:24 AM

it is an induction motor 5kw 480v 3 phase 60hz.

i want to know what will be the effects when it will be run on 400v, 50hz.

will the current increase or decrease?

what will be the impect on power fector, cooling, winding, hp etc?
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SUBBARAOY
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#7

Re: 50Hz vs 60Hz

02/20/2012 6:35 AM

WHY U REQUIRE TRANSFORMER ONLY SOME SPEED WILL REDUCE. IN UR CASE IF SPEED IS NOT A PROBLEM U CAN USE THE SAME MOTOR
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iftikhar129
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Join Date: Dec 2011
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#8
In reply to #7

Re: 50Hz vs 60Hz

02/20/2012 11:28 AM

http://www.usmotors.com/TechDocs/ProFacts/Voltage-Frequency-Variation.aspx
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arifkunnath
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#10
In reply to #8

Re: 50Hz vs 60Hz

02/21/2012 12:14 AM

This site says slight variations from designed parameters are acceptable, and it will not harm much on the performance of the motor. But its good to be used at designed voltage and frequency.

In India we experience under voltage/under frequency conditions and some times over voltage/over frequency conditions . If these are with in the tolerance limit we used to manage with it. But its risky .
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visaseller
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#11

Re: 50Hz vs 60Hz

02/21/2012 9:08 AM

Why you want to step up.... by calculation u should achieve rate RPM and torque.... 480*(50/60)=400V
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JRaef
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#12

Re: 50Hz vs 60Hz

02/21/2012 10:44 AM

Motors provide power (kW or HP) which is torque at a given speed. Speed is a function of the number of poles and the supply frequency, torque is a function of the V/Hz ratio. As long as you maintain the V/Hz ratio within 10% of the original design, you will get full torque out of it. 460/60 = 7.67:1, whereas 400/50 = 8:1, well within 10% so no problem with torque. Speed will be 17% lower at 50Hz, so then your power (kW) will be lower.

If you boost the voltage to 480V but not the frequency, then the V/Hz ratio will no longer be in tolerance. 480/50 = 9.6:1, which is 25% high, the motor will saturate and burn up.

You only need a VFD if you must have the speed correct or the power to be the same. If so, then you must still boost the voltage to 480V ahead of the VFD so that it too can provide the correct V/Hz ratio.

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iftikhar129
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#13
In reply to #12

Re: 50Hz vs 60Hz

02/22/2012 9:06 AM

nice proceedings....

Can any one write here the exect formula which showes that increasing v/f ratio will saturate the core resulting in motor burning.?
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rodeh
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#14
In reply to #13

Re: 50Hz vs 60Hz

02/26/2012 5:33 PM

Hi ,

They are 2 approximation to show the loss in torque VS speed.

One is proportional to V/F ratio

The other is proportional to (v/f) ^2. Both are firly accuarate .

You only need to set your motor name plate for 60 HZ and set the voltage 480 Volt. the run the motor at 50HZ.

You run the VSD in V/F mode then set your reference speed to 50HZ.The VSD will adjust voltage accordingly.

I donot see any need to rewind the motor or use a step up transfomer unless your motor size is almost matching the load then you may loose some torque due to V/F effect. I amassuming you running variable torque application.

I suggest you contact your nearest Schneider Electric branch so they can help you select the best VSD for your application.
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Users who posted comments:

arifkunnath (2); Crabtree (1); dvmdsc (2); iftikhar129 (3); JRaef (1); rodeh (1); SolarEagle (1); SUBBARAOY (1); Tornado (1); visaseller (1)

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