Help with electric motor please.

[oakwoodtv]

A1 A2 will be the run winding and Z1 Z2 is the start winding with a capacitor in series.

to reverse rotation reverse Z1 Z2 winding.

This may help      http://www.sentridge.com/wp-content/uploads/wiring_1ph.pdf

[Julian]

I've looked at that diagram, but the two windings have the same resistance ... I thought start and run windings usually had differing values, also there's no sign of a capacitor ever being fitted to either motor, but I agree, the little I know of single phase motors says there should be a cap some where in the circuit.

The second motor has a seized bearing, so trying that is a non-starter.   I think the one I'm tying is in OK condition given the windings are open circuit to ground.

I think I'll have to try linking Z2 and A2 and stick mains on either Z1 and A 1 or Z2 and A2 and see what happens.

This is for the belt grinder mentioned some time back ... I decided the treadmill motor was too small for use with metal, but the speed control would nave bee a major benefit,  To that end I have a three phase motor which I'm toying buying an inverter for ... may be a better solution all round (with the exception of setting up the inverter ... they look very complicated!)

[knighty]

you could stick negative to the link bar and positive to either of the other two (try both) - see what happens, nothing to lose :-)

[oakwoodtv]

I would connect mains across A! A2 with a cap from A2 to Z2.

Value is a bit tricky about 10 to 15uf per HP so 3.5 or 4uf. 

[Julian]

Tried linking A2 and Z2 and putting mains on A1and Z1 which blew a 3amp fuse.  Tried again with a 5amp fuse and it ran but very slowly.

Tried wrapping cord round the shaft all same lawn mower and tugging so it was running at speed when I switched it on the next time and it ran at circa 1100 rpm ... rather noisily!  After a few seconds I got this "things are getting rather warm" smell, so switched it off.  Over the course of a few minutes het heat percolated through the casing to become rather warm!

I don't have one, but is a capacitor likely to get the thing running OK or am I on a hiding to nothing?

[oakwoodtv]

Try connecting mains across A1 A2 spin the shaft with the rope then switch on the power.

It should run OK with no load and not get hot.

The cap from a tam 105 8uf should be ok to try. 

[Julian]

Sorry, got that wrong ... I connected the mains on A1 and A2 ... as I stated above would have been a dead short!

So you reckon A1- A2 without the second link?

I do have a TAM buried somewhere but physically this motor is 3 or 4 times the size of a TAM

[oakwoodtv]

The tam 105 motor is also 1/3 HP I would not worry about the physical size.

[Julian]

Electrickery is truly a mysterious and wonderful thing … mains to A1 and A2, link between A1 and Z1 and an 8µf capacitor from a Leo between A2 and L2 and it works.  No noticeable heat from the motor, no noticeable heat from the capacitor and it spins at 1485 rpm (varies a bit) … thank you Richard for your assistance, much appreciated.


Just a thought … isn't the synchronous speed for 50hz 1450 rpm?  Could the capacitor rating effect the speed?

[oakwoodtv]

No  the synchronous speed for 50hz motor depending on the number of poles is 1500 [for a four pole ie two pair motor

50 x 60 divided by two = 1500 .

The actual speed will always be slower due to slippage.