Running 60HZ motors at 50HZ
Running 60HZ motors at 50HZ
(OP)
I have been presented with a situation where 110V/60Hz refrigeration equipment has been installed in a 230V/50Hz environment. A step-down transformer has been installed to reduce the input voltage to 96VAC/50Hz. From reading FAQ237-1224: Motors: Changing between a 50 and 60Hz supply. (very good by the way) this seems to go partway to solving the V/F problems described in that FAQ. Doing the math the input voltage should be reduced to somewhere aound 91VAC/50Hz. My questions are as follows:
What is the overall impact on energy consumption?
What is the overall impact on equipment longevity?
What is the (in general) reduction in system efficiency?
These units are installed in a marine environment where energy consumption is a major consiteration.
Thanks for any info! Rob
What is the overall impact on energy consumption?
What is the overall impact on equipment longevity?
What is the (in general) reduction in system efficiency?
These units are installed in a marine environment where energy consumption is a major consiteration.
Thanks for any info! Rob





RE: Running 60HZ motors at 50HZ
Glad you like the FAQ.
Now to your questions.
Since refer equipment is positive displacement I would believe you'd see about a 1/6 reduction in energy consumption.
Equipment longevity would probably go up about 2/6th probably because the pistons and bearings would see the slower speed AND the maximum temperatures of the pistons, and windings, and everything related, would be lower and less stressful.
System efficiency.. Hmmm harder call. Very hard, in fact, if you take in all things like the generator, battery draw, inverter loading, cycle time, battery charging fuel consumption, generator run time, etc.
The problem is that refer equipment is designed right up to the 'edge' for cost and efficiency reasons. If you then run the system at a substantially slower speed (17%) you may find the system capacity has been reduced perhaps more than 17%. This means during that struggle to reach cutout where heat leaks in while on the other side you're trying to pump it back out you will be executing a stern chase, as it were.
The system may have to run considerably longer to achieve cutout.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Running 60HZ motors at 50HZ
I wouldn't worry too much about the 91V vs 96V by the way, the tolerance is +- 10% anyway, so that should be fine.
RE: Running 60HZ motors at 50HZ
Ahem. Ah RobSimon; One thing you didn't mention was the size equipment you are referring to. If this is single phase equipment you may well have really poor efficiency since any start switch may not achieve transition resulting in a total burnout. (= 0 eff)
Also do you already have this equipment?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Running 60HZ motors at 50HZ
RE: Running 60HZ motors at 50HZ
Single phase 110V/60Hz with about a 6 amp running draw sized to be handled on a 15 amp circuit. I have not been able to get more information from the manufacturer (Sub Zero)
In the FAQ noted above generated heat and loss of cooling was pointed out as a major factor. Should we be concerned about that in this application?
Finally, the manufacturer has suggested that instead of reducing the voltage to 96V as is presently installed, the voltage should be INCREASED to 115Vac. This seems to contradict everything that has been stated in the FAQ. Any suggestions on why they would feel that this is a solution?
The boat will be in tropical waters and thus will be in the worst possible environment should they already be operating on the margin. The units are air cooled. The present time is the best to implement any modifications or replacements should there be any serious concerns.
Thanks again. Rob
RE: Running 60HZ motors at 50HZ
RE: Running 60HZ motors at 50HZ
You may need different fan blades.
Leave things at 96V that's fine. Raise it? I believe they are making a mistake.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Running 60HZ motors at 50HZ
Speed switches, no.
We need some help from someone who is current on small hermetic units.
It may be worth considering purchasing 230V/50HZ hermetics and having a refrigeration man swap them out. Keep the "Sub-Zees" but change the compressors. If you go that far, investigate adding water cooled condensers.
I wouldn't consider using 115V/50HZ unless you get it in writing from Sub-Zee. You won't get it in writing.
respectfully