You need "delta" connections, but the motor is wired "star". I don't know if the wiring can be re arranged, hopefully someone will know. If you bought a new motor it would be easy to change from one to the other, but the mountings and shaft diameter might have changed.

Davey, looks like the 3 ends of the coils are all connected on the terminal marked N to provide star connection.

You need to remove these and place in 3 separate connectors so you will have 6 ends in the terminal box, then check for continuity between ends to find the ends of coils.

If you have 3 coils of almost equal resistance you need to connect them in Delta to allow the use of a 230v VFD.

Emgee

What you have got is three phases going into your motor which connect together at the neutral terminal. To change to delta, you have to disconnect the three neutral wires and move them to the appropriate phase connections. The neutral terminal will now have no wires going to it. You need a meter with a low ohms range to find out which wire goes where. My poor diagram shows what it should look like Good luck. Check the connections when the wires are disconnected from the neutral.

Edited By old mart on 28/09/2019 22:38:02

Could you kindly describe or post a credible diagram showing how it is possible to put the windings in an incorrect orientation.

Reversing the ends of any winding is exactly the same topographically as swapping over two wires of the supply. This is the standard method of making the motor turn in the opposite direction.

Without going into too much motor theory, hope this helps to explain:

Reversing a 3 phase motor involves changing the phase rotation, there are only 2 possible phase sequences for a 3 phase system 1-2-3 or 3-2-1, reverse any 2 phases and the motor changes direction.

However, reversing 1 winding will not reverse the motor. Each winding is electrically oriented to produce the required N-S magnetic field, as the phase rotate around the connections, so the N-S field in each coil progresses round the stator, effectively ‘pulling’ the rotor with it. Each coil in the stator is not a single winding but several that are interleaved so the stator is magnetically connected at multiple points around its axis. Swapping the orientation of one of these field winding groups essentially puts part of the rotating field into a S-N magnetic orientation in relation to the other windings and will therefore ‘buck’ against the rotation. Invariably this will prevent the rotor spinning and cause excessive heat in the stator windings eventually burning out the stator.

Must be an old motor. The rating plate certainly implies it's a dual voltage motor, but the connection box isn't what you'd expect. I'll leave it for someone with more knowledge to suggest a wiring arrangement.

Incidentally a star connected motor will run just fine off an inverter producing 3-phase at 230V phase to phase. The issue is that the phase currents, and hence torque and power, will be down by a factor of 1.732, aka the square root of three.

Andrew

When I wired my mill up to 220v delta I used the following procedure to ensure correct polarity of the windings. I noted the colours/terminal designations which related to each winding on a post it note. I just used a multimeter rather than a zero centre one and watched which way the needle tried to kick.

i) With a multimeter or continuity tester, you can segregate three sets of windings.
ii) Now, assume one set of windings to be, say, winding "U" and also, designate its terminals as assumed "U1 & U2".
iii) Take a 9V Cell; Connect + ve of Battery to the assumed "U1" preferably thro a push-switch and – ve to the assumed "U2".
iv) Connect a zero centred galvanometer, to another set of winding, say winding "V" such that the assumed "V1" is connected to the + ve terminal of the galvanometer and the assumed "V2" to the – ve terminal of the meter.
v) Now, when the switch is pressed, the zero centred galvanometer would deflect in the positive direction, if the assumed "U1, U2, V1 & V2" are correct.
vi) Else, if the deflection is on the negative side in the galvanometer, change your assumptions for either one of the winding (That is may be the assumed U1 can be U2 and the assumed U2 is U1 . Or keep the assumptions for U winding as it is and reverse it for the V winding (that is assumed V1 is V2 and assumed V2 is V1).
vii) Repeat this test for applying voltage to other windings and confirm your terminal assumptions.

The reason the winding polarity is critical is that the windings must have the proper phase to generate a rotating magnetic field to drive the rotor in a given direction. If one of the windings has the wrong polarity then that winding will be trying to rotate the field in the wrong direction. This causes poor motor torque and generates high winding currents.

HTH

Edited By bill ellis on 29/09/2019 10:17:51

Pay attention there at the back.

That's not what I wrote. If you run a motor in star and at a phase to phase voltage of 240V instead of 415V then there will be a loss of power compared to running at 415V. That's why when running from an inverter that gives 240V phase to phase you need to change to delta to avoid the power loss.

Andrew

Davey, my Fobco drill has a similar motor, I would have to take the motor off to see the motor plate. The lid of the terminal box shows how to connect for high and low voltages. It is probably the same as your motor :

From studying the photographs, the colours of the op's wires are the same as the motor plate diagram. This would make it easy to get everything connected correctly.

RED-BROWN

YELLOW-WHITE

BLUE-BLACK

The 3 input wires can be connected any way round, only swapping any two if the motor rotates the wrong way.

If the 'star point' is accessible and it's wired correctly, then the correct wiring for delta sees each of red, yellow and blue connected to one of of the star point wires that doesn't belong to the same coil.

Your winding connections are the standard colours of red, yellow blue and Brown, white, black so the connections in MIchael Brigg's photo are standard.

There is no earth connection to ground on that inverter?