Rzn Posted October 12, 2006 Report Share Posted October 12, 2006 Dear All, I have some Asynchronous motors in our company's central stores which have no name plates. I have only data of motors as 400VAC, 50HZ and RPM (mostly 1450RPM). My question is that how can I check the KW raiting of motors? Rizwan Packages Ltd Link to comment Share on other sites More sharing options...
jraef Posted October 12, 2006 Report Share Posted October 12, 2006 Do you have a way to connect them to a variable load? If so, you could add loading to them while monitoring current and power factor. Whewn the power factor reaches .80 you can measure the current and estimate the kW rating from that using the formula kW = V x A x pf x eff (assume 93%) x 1.732/1000. It would not be exact, but it would be close. If you don't have a way to do that, you can connect them and run them open shaft. Most motors run between 20 and 30% of FLA when open shaft, so if you divide the unloaded current reading by .30 you will get a conservative estimate of FLA, which you can compare to similar motor designes to get a kW estimate. That method is going to be much more inaccurate than the other, but if it's your only choice it may have to do. "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
Rzn Posted October 13, 2006 Author Report Share Posted October 13, 2006 Thanks a lot Mr. Jraef Link to comment Share on other sites More sharing options...
GGOSS Posted October 17, 2006 Report Share Posted October 17, 2006 Good work jraef. Regards, GGOSS Link to comment Share on other sites More sharing options...
jraef Posted October 17, 2006 Report Share Posted October 17, 2006 As a follow up, I just read somewhere else that unloaded current can be anywhere from 20 - 50% of FLA, so that method may be even more inexact than I previously mentioned. "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
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