60 Hz design, 50 Hz operation 2

[robertfortney]

Hello everyone. I hope someone here can assist me. I am a Structional Engineer so I am unable to assist one of my clients with this relatively simple question. This person has a water feature with a US built 120/60 Hz motor but they are located in a country with a 220/50 Hz power supply. What will happen to the motor, (short term and long term), if they choose to use it in this application?

They are concerned with any potential damage to the pump motor, increase or decrease in the amount of water flow over thier waterfall, increase in electrical consumption or costs, etc. Poorly designed pumps are available locally but they want to know what will happen to their pump if they choose to use it under these electrical conditions.

It is my understanding that operating a 60 Hz motor at 50 Hz, will slow the pump by 20% and decrease the pumps ability to cool but since this pump is completely submersed under water, over-heating should not be an issue. My primary question is what are the potential problems that could arise if my clients choose to use this pump?

Can they use the pump as is with no serious effects? Is there a simple and/or inexpensive way to remedy any potential problems. etc.

Thank you for your time in clearing this up for me.

 

[ScottyUK]

You are correct, the pump will run more slowly. It will develop less head, unless it is a PD pump, and move less fluid. You can use a transformer to correct the voltage mis-match, but you need to maintain the volt/Hz ratio so you need a 220/100V transformer. Or you can buy a pump from the 50Hz world and just use that. There are plenty good brands available - where are you sending this item?

 

[robertfortney]

Scotty, first of all, thanks for the reply. I am not sending the pump anywhere. A client of mine has relocated to New Zealand for long term business. They are quite partial to their water features and have taken their state of the art, top-line pumps and filters with them. They are aware that the easiest thing to do would be to buy a 50Hz pump but asked me what would happen to their pump if they just go ahead and use it anyway.

The problem is that their current pump is pre-designed with all of the attached fittings, valves, ultra-violet sterilizer, filters, etc. for use in their existing water feature which was disassembled and moved to New Zealand as well. It is a wall fountain that is completely enclosed. Technology in the water feature market place in New Zealand is not as advanced as it is here in the US and the local contractors are wanting to completely redesign their feature to handle plumbing, filtration and pumping systems used in New Zealand, (which means tearing it apart and rebuilding it).

They really do not want to do this...

They asked me what would happen if they just plug-in their 60Hz pump and run it anyway.

I was not sure what to tell them. Will it run? Will it fail? Will it even move an adequate amount of water? The dynamic head on the entire system is only about eight feet.

Thanks for any information that I can pass along to them.

 

[ScottyUK]

Do you know what type of motor the pump uses? It is possible to use some - but by no means all - single phase motors with a variable frequency drive which would allow it to operate at 60Hz. You could buy an over-sized drive designed for 220V/240V input and program it to produce 60Hz and 120V output, or use a transformer to drop the voltage first. The drives designed for this type of duty are quite expensive relative to their 3-phase counterparts, reflecting their limited market. The only brand name I can recall is the Optidrive by Bardac, although I stress I've not used this brand myself. Maybe one of the other members can chip in with some practical knowledge...?

http://www.bardac.com/pages/products/ac_optidrive7.html

 

[DRWeig]

Good thought, ScottyUK. I'm not sure how to select one for that application either.

For robertfortney, here's the 50/60 FAQ for this forum:

http://www.eng-tips.com/faqs.cfm?fid=1224

Best to you,

Goober Dave

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