60 hz vs 50 hz

[Cody K]

Hello all, we have a small what we call "plant" with around 10- 480v 3 phase 60 hz motors. Our saleman is talking to a customer in Russia that has 380v 50hz system. My question is that will our motors work correctly, other than the speed? None of the nameplates mention 50 hz or 380v as some others apperantly do.

Our control equipment consists of stepping down 480v to 240/120v (cutler hammer single phase transformer) which we run Allen Bradley plc's and Cutler Hammer A-200 starters. The cutler hammer transformer's nameplate says it is rated for 50 or 60 hz.

Thanks

Cody

 

[BAHTAH]

Motor Rating Variations

Motor Rating Variations

Hello all, we have a small what we call "plant" with around 10- 480v 3 phase 60 hz motors. Our saleman is talking to a customer in Russia that has 380v 50hz system. My question is that will our motors work correctly, other than the speed? None of the nameplates mention 50 hz or 380v as some others apperantly do.

Induction motors typically will operate at their rated frequency and rated load with a voltage variation of up to 10% (NEMA MG 1, 12.44) They will also operate successfully at rated load and rated voltage with up to a 5% variation in frequency. This would put the minium voltage for a 460V rated motor at 414V and the Max at 506V. Frequency variation for a 60hz rated motor would be a minimum of 57hz and a max of 63hz. The problem with these variations is they effect the total motor performance with respect to speed, efficiency, operating temperature, torque etc. A constant operating temperature increase of 10 deg C can reduce the motor insulation life by as much as 50%.

I would advise you investagate getting the proper motors for the application especially since your company reputation will ride on the quality of your product here and in foreign markets.

Grant

 

[templdl]

I don't have my referrence material here at home but I know a 60hz transformer will run warmer at 50HZ and would have to be derated.
There is more core material in a 50hz transformer.
It is similat in an induction motor. the lower frequency causes more heating.
Motor change electric power into work. In the process the give off heat.
In order to keep the motor within its temperature rise rating a 60HZ motor would have to be derated in order to run a 50HZ and as such would not provide its name plate HP rating. Again I don't have my referrence material to provide an estimate of the loss of performance.A 50hz motor will work better a 60hz than a 60 and 50hz.

 

[coulter]

...will our motors work correctly, other than the speed? ...

Yes they will work fine. The important issue is to keep the volts to hz ratio the same. As long as you do that, they will run fine.

As you said, the speed will be slower, infact 5/6 slower, so a 3600rpm motor will turn 3000.

As templdl said the hp is also lower. That is because the speed is lower. The motor will put out about the same torque, but since the speed is 5/6, the hp will be 5/6. No magic here, just look at it as if you were using a vfd at 50 hz.

Now as for if the motors will put up enough hp for the application or if the speed difference is significant to the application - you're going to have to pay for some engineering.

carl

 

[kingpb]

I would not recommend doing what your propose, for the simple reason that when the motor does require replacement, it is going to be very difficult to get a US motor in Russia, and with the way things are going, maybe even more difficult then expected.

IMO you will be doing the customer a disservice by not providing the equipment based on the actual nameplate ratings for his location. 380V 50 Hz motors are readily available around the world, if your going to be a worldwide company then you need to get the right equipment.

 

[hillbilly]

In the past I've built and shipped equipment into South America, and most of the time the local voltage was 380/3/50.

I always supplied 480V/3/60 motors and de-rated the HP.
I usually had the motor supplier provide new tags for the motors showing the corrected HP and RPM.
The motor RPM will be 5/6 of the base speed listed on the 480 Motor.

I normally used 240V controls on these machines because it (220V/1)
is readily available on a 380V 3 phase suppply.

As long as you de-rate the HP, you shouldn't have any problem.

Hope this helps
steve

 

[petersonra]

I would not be too concerned about it. You may need to do a little figuring to make sure. As another poster suggested, it may be an issue to your end customer as far as spare parts goes. Locally available motors in Russia may not even have the same mounting face.

 

[tony_psuee]

check with supplier

check with supplier

We frequently use 460V/3/60 motors on 380/3/50 applications. However, we have the vendor renameplate the motor. They supply it with the same HP rating, but a 1.0SF instead of the standard 1.15SF.

tony