AC Motor Converter


Thread Starter

Duc Pham

I have a motor 20HP, 460V and speed 1170RPM. I want to reduce the speed by half(600RPM). What should I do to reduce the speed by half that the torque of the motor still the same. I think I should buy a convertor please tell me which one and where I can find it. Anyone please give me some advice I am very appreciated.
Thank you for your help.
Best Regard
Duc Pham
Unless I miss understand your question! But You do not lose torque by going slower, you loose torque by going faster.
Duc Pham,
A 2 to 1 gear reducer will cut the speed in half
and double the torque. Look up gear boxes or gear reducers on the net or in your locale.
Tom Bullock

Abdullah GAYRET

Dear Duc;

I understand that you should use frequency convertor to reduce speed how much you want.If you apply half frequency of motor by convertor, you can provide half speed. I can recommend convertors below, you should buy it from any
Siemens Distributors.

Best regards,
Abdullah Gayret

Siemens Micromaster Eco (6SE 9523-0DG40) 15 Kw.
or Siemens MicromasterEco(6SE 9523-7DH40)18,5 Kw.
I believe you still don't have an inverter and you're running your motor from mains via protectors, meaning you're current application is constant speed. Now, you want to use it for an application at half the speed at the same torque. Is this the case in hand? Then, you need an inverter, a simple one will do, meaning the type of feedback control can be simple, since you will be using it at two speeds only. However, the next issue will be the derating of your motor because it is probably self cooled by fins connected to the shaft, at half the speed, cooling is greatly reduced by a square of the speed reduction. So, address the heating that will come as a result of the speed reduction.
Thank you for your reply, can you advice me what should I do or what equipment I should add to reduce the speed by half of my motor and where can I buy it.
Thank you for your help.
Best regard
Duc Pham
If you want variable speed, you can use a AC inverter. Torque won't be a problem. But, since you are talking about 20Hp the pricecard could be big. Maybe, if you have enough with a fixed speed, you could fit a gear box. Another solution is to buy another motor, maybe this will be the best and cheapest solution!
To combine some suggestions and points made in other posts:
A 2:1 gearbox would be the easiest way but 2:1 gearboxes are not that readily available. Another way would be to just put a 2:1 timing belt drive but be advised that this is going to double your torque (Maybe you only need 1/2 the
HP that you think you do?)
Check out Goodyear or Gates or Dodge for timing belts and pulleys.

[email protected]

Kevin Seifert

ABB makes variable frequency drives that would fit your application. You can call me for more information.

Kevin Seifert
Fluid Solutions Company
Atascadero, California