Electric Motor

I have just bought a Single Phase 3hp motor second hand for my Colchester Lathe, it works fine, the information on the Name plate is puzzling me.

V 230/250 460/500

Kw 2.2

Speed1420

Does this mean that this motor is 2 speed.

It 'could' also mean that it is a dual voltage 3 phase one. Are there any capacitors strapped to it. (tubes)

Any chance of a photo of the connection terminals.?

Nick

Edited By Nick_G on 27/04/2014 00:38:33

The motor has two windings that can be connected in parallel for 230/250V and in series for 460/500V. The latter is very strange! Phase to phase at 250V is 435V so I can't see where you would find 460-500V.

Speed 1420 rpm is a little less than 50Hz per minute divided by two so it's a 4 pole induction motor. It's probably got a capacitive starter winding but it may be using a shaded pole or even a high resistance starter winding.

If the cooling fan is rotating freely and quietly and is sucking air in and then along the motor fins then it will probably run longer than you will.

Colin

Thanks for your replies Gents, this is a Pic, it does have a Capacitor it runs smoothly it is powerful the fan is running it does seem a nice Motor, just wondered about the dual voltage.

John,

I too wonder about the dual voltage.

Changing the windings on an induction motor is a standard three phase trick to give you a lower starting current. The motor starts in a star configuration with each winding connected to a phase and neutral and then switches to a delta configuration with each winding connected between two phases.

However I can't see anything like that working on a single phase motor. All I can say is that I would be very surprised if the windings could be rearranged to switch from a 4 phase induction motor to a two or an eight phase induction motor and hence give you a factor of two speed change. (I daren't say impossible as I'm supposed to know things like this.)

I doubt if you'll ever get close to needing 3 HP from this motor but if you do then it will get very hot. At the same time I would also expect your power cord to get noticeably warm and most 13A plugs and sockets to get very hot and unhappy. But for home use, relatively gentle cuts, and no time pressures then almost any electrical set up will work safely, just make sure the earth is connected and, if you can afford it, use a 30mA RCCB, residual current circuit breaker.

Regards, Colin

Further to Colin's tip about using a 30ma RCCB (Residual current circuit breaker) my advice to all who have a workshop is you cannot afford NOT to have such a device either in the main power supply or better still on individual power circuits, they are proven life savers.

Rgds, Emgee

Thanks again for your replies in particular to Colin who obviously knows his motors, here is a pic. of the plate on the motor it looks like someone has tried to clean it and maybe rubbed off some info., do you think the 1 under the 2 of 12172 represents 1 phase.

A better pic. of the connection box neutral input to top left terminal, input live to top right terminal, I think the capacitor goes on middle top and middle bottom.

Attached is a pic of the data plate of an American dual voltage single-phase motor I have been discussing on another forum.

Perhaps the connection diagram might give the experts a clue as to how yours is set up.

I would think that the "1" you mention does indicate the phase, below that is a "50" for 50Hz, but no idea what the "160/200" is.

It sure draws some amps on the low voltage - 17.9 as against 8.75 on the high voltage.

Thanks for the info Robbo, with regard to the current the first voltage is half the second, does it not follow that the current for the second voltage would be half the current for the first voltage which it sees to be.

John,

Referring to your name plate;

2.2 kW = 3 HP, so far so good.

The 1 probably refers to single phase.

At 240V and a pessimistic power factor of 0.85 the full load current will be 2200/(240*0.85)=10.8 A (At 480V this drops to 5.4A)

Therefore the 17.5 and 8.75 make no sense to me.

The B comes from the insulation temperature rating of 130 degC.

If the motor is running then I wouldn't try to "improve" anything. However, I can't tell whether this kind of motor uses the capacitor just for starting or continuously. The latter needs a more expensive item and may have been inadvertently down graded. A clamp on ammeter should tell you whether the capacitor is handling current all the time or, more crudely, a finger on the capacitor can should reveal whether it's getting too hot. Did I mention using an RCCB?

I wonder if the 17.5/8.75 and 160/200 refers to the starting capacitor specifications? 17.5 uF at 160V for 240 V operations and 8.75 uF and 200V for 480V operations. Nah, those values look way too small.

Good luck and be careful, Colin

Thanks Colin for your input, the motor does seem to run ok it does not get hot, there is quite a "hum" from it when it is running, I am using a RCCB.Regards

.

I see on one of the wires it says Z2, the usual set uo for this notation is A1 and A2 are the run winding. Z1 and Z2 are the start winding. to reverse the motor reverse Z1 and Z2. It is a "Kapak stayrite" motor made after GEC merged with AEI as "stayrite" was an AEI "brand", continously rated (will run continously without overheating). Are the two red/orange wires the capacitor? Google Kapak stayrite and you get lots of pics and info.

Phil

Hi Phil, Thanks for this usful information, yes the two red/orange wires are the capacitor and go to bottom left and bottom middle terminal not as I originally stated.