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Model Forum / General / Models / February 2009Motor ID help requested
I have a 3 phase motor picked up on flea bay with no markings or ratings on it whatsoever. It is TEFC 100 frame size aluminium clad foot mounted and the body is 220mm long excluding the fan. It is a 6 pole machine (950 ish rpm on 50Hz) The shaft is 28mm diameter which points towards 2-3 hp but the winding resistance is 9 ohms measured from star pint to each winding it seems to run ok on 415v star and 240 delta. Looking at other motors I have with rating plates eg a 1.1kW, 4 pole has a winding resistance of 6.7 ohms. I 'm surprised if the unknown motor can be 2-3 hp (1.5- 2.2 kW) with such a high winding resistance. Can anyone suggest what the power rating of the motor might be? TIA Bob >I have a 3 phase motor picked up on flea bay with no markings or ratings on >it whatsoever. [quoted text clipped - 16 lines] > > Bob It's possible that it's a low duty cycle motor so they weren't too worried about I2R heating so used thinner wires. I've not had much luck sizing motors from frame sizes as it's very dependent on the age of the motor amongst other things. Martin  Signaturemartin<dot here>whybrow<at here>ntlworld<dot here>com >>I have a 3 phase motor picked up on flea bay with no markings or ratings on >>it whatsoever. [quoted text clipped - 21 lines] >amongst other things. >Martin Winding resistance is a better indication of HP than frame size. All things being equal a six pole machine would only be 2/3 of the HP for the same frame size. 18 ohms terminal to terminal for a largish 415 volt machine is pretty high but if this is the confirmed resistance I would expect a rating of no more than 1 HP. Jim > I have a 3 phase motor picked up on flea bay with no markings or ratings > on it whatsoever. [quoted text clipped - 16 lines] > > Bob Only 100 frame 6 pole motor listed in the Fimec book is 1.5 Kw [ 2HP ] resistance will be higher on a 6 pole than a 4 pole because it has more copper. Somewhere I do have brand new 2Hp 6 pole and if I find it I'll run a check on the resistance. John S. >> I have a 3 phase motor picked up on flea bay with no markings or ratings >> on it whatsoever. [quoted text clipped - 25 lines] > > John S. Thanks John, You are a gent! Bob > I have a 3 phase motor picked up on flea bay with no markings or ratings > on it whatsoever. [quoted text clipped - 12 lines] > > Can anyone suggest what the power rating of the motor might be? I have a 2.5 hp at 940 rpm motor built by Laurence, Scott & Electromotors in 1931. It is huge compared to your motor. Weighs almost 100 kg. It is connected delta for 400 V, which is unusual. Shaft diameter is 1 1/4". The resistance of an individual winding, when disconnected from the others, is 6.5 ohms. Here's the motor: http://www.mythic-beasts.com/~cdt22/lse_elec_motor.jpg And here's the data plate: http://www.mythic-beasts.com/~cdt22/lse_motor.jpg A long time ago I did possess a modern six pole, single phase motor of a similar physical size to yours. It was made by Brook Hansen. I swapped it for some other motors, but I checked my old e-mails and it was 0.5 hp and weighed 14 kg. I don't know if this information is of any use to you, but feel free to ask further questions if necessary. Best wishes, Chris >> I have a 3 phase motor picked up on flea bay with no markings or >> ratings on it whatsoever. [quoted text clipped - 37 lines] > > Chris Thanks Chris. Your motor is certainly a big beast! I suspect this reflects it age and the weight will be the mix of conservative design of that era and lots of cast iron. I also suspect the use of thicker wire and hence the low resistance. Yes it is unusual to see this as 400v delta. Maybe for star/delta starting perhaps? My motor is relatively modern and so I suspect similar to the one JS has stashed away. Hopefully when he next trips over it he can let me know the resistance. If you been to John's workshop you will know there are lots of things to trip over - lol. It makes Aladdin's cave look empty by comparison! Cheers Bob > Your motor is certainly a big beast! > I suspect this reflects it age and the weight will be the mix of > conservative design of that era and lots of cast iron. Actually, the body of the motor is stick welded mild steel, which I think was rather unusual for the period. Only the end bells and fan cowl are cast iron. The rotor is stick welded too. It has a passage for air through the centre, with a soldered cage of copper bars around it. > I also suspect the use of thicker wire and hence the low resistance. > Yes it is unusual to see this as 400v delta. Maybe for star/delta > starting perhaps? Possibly that was the designer's intention, although it wasn't wired in a way which would permit star-delta starting when I acquired it. I think star-delta starting would be unusual for a motor of 2.5 hp. > My motor is relatively modern and so I suspect similar to the one JS has > stashed away. Hopefully when he next trips over it he can let me know > the resistance. If you been to John's workshop you will know there are > lots of things to trip over - lol. It makes Aladdin's cave look empty by > comparison! I haven't had the pleasure :-). Did you ask the eBay seller about the motor's history? They might be able to tell you what kind of machine it came from, and from that you might find the specification. I have a very old commutator motor sitting around which doesn't have a data plate. Probably about 3/4 hp. It runs without any problems through a variac. It has quite a distinctive case design. I saw another motor on eBay with the same case design (but definitely a different model). It was labelled "Batwin" but I haven't been able to find any further information. Best wishes, Chris > I have a 3 phase motor picked up on flea bay with no markings or ratings > on it whatsoever. [quoted text clipped - 16 lines] > > Bob motor on my 3 phase die filer is a mammoth its only 1 hp yet is about 1 foot in diameter and 16 inches long. all the best.markj |
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