Inverter wiring Again

Paul, do you have any information from the motor's rating plate? Is the inverter a 'normal' type, i.e. Vin =230V and Vout =230V. Assuming the motor is a 230V/440V type and the inverter is 230V out, you'll need to wire it for delta operation. Assuming that the motor ran as it was wired before, then 1,3 and 4 were the star point, so the windings are 1(A)-5(A'), 3(B)-6(B') and 4(C)-2(C'); you want to connect A toB' B to C' and C to A' and connect your power to the 3 points A, B and C (you can interchange B/B' for C/C' if the links are easier to connect). Nearly all motors I've seen have the terminals arranged so that the links fit directly between opposite pairs of terminals to make wiring up more simple, e.g.

Hi Martin

Yes the inverter is 230V in 230v out. Sorry I forgot that bit.

Motor is 230/440V 50Hz 1125RPM

Yes the motor ran as I saw it under three phase power.

So basically I connect

I can then connect my 3 wires to ABC i.e.

Does this sound OK or have I got it wrong?

Also does it matter if A,B, or C are connected to U,V or W from the inverter?

Thanks again

Paul

Hi Paul, yes that sounds OK. You can connect U,V and W in any order; if it runs the wrong way, swap any two of the U, V or W wires around so that forward on your inverter matches forwards on the lathe. A quick check, after you've wired it but before you connect the inverter, is to measure the resistance AB, BC and CA, they should all measure the same within a few %. Martin

I'm no expert on these matters but it seems to me that jumpering pins as listed, e.g. 1 to 5, would short out the three coils. A typo or am I missing something?

Martin's reply does not show connections like that and makes more sense.

Henry

Hi Henry

Yes I think you are right. The continuity would a coil so as you say I think it would not be good to connect those pins together. John S posted a pic of a before & after inverter job but the pins on that motor were in a different configuration than mine and I think I misunderstood the info being presented. After reading Martins reply it seems a little clearer now. I`m certainly no expert on electrics and least of all 3 phase. I think if I follow Martins instructions I should be Ok but any more info advice gratefully received.

Thanks again to Martin for the replies.

Paul

Hi Martin

I`ve connected the jumper plates as above i.e

pin 1 connected to pin 6

pin 3 connected to pin 2

pin 4 connected to pin 5

All the links do fit with no problems.

I checked the resistance directly from pin to pin with no wiring yet attached (only the links) and got the following:

A To B (pin 1 to pin 3) around 20 ohms

B to C (pin 3 to pin 4) around 20 ohms

C to A (pin 4 to pin 1) around 20 ohms.

All resistances are the same give or take 1/2 ohm.

Does this seem OK?

Cheers

Paul

That sounds OK Paul.

I always feel that thinking of the diagrams of star (or Y) and Delta helpful. Separate all windings and then reconnect either a star or delta. Delta voltage is always the lower voltage to the two settings. This is logical looking at the diagram. Star voltage is root 3 * delta voltage. Simplest just to remeber this than try and understand.

Irrespective of the configuration, swapping any one winding end for end with respect to the others will just reverse rotation as will swapping any pair of wires between the motor and the inverter. Most inverters will allow swapping primary direction of rotation in a menu somewhere so that 'forward' can be defined as normal for the application and reverse being the other way.

Good Luck

Bob

Like Bob said, yes that looks fine. Martin

Hi Folks

Finally found some time to sort out my inverter wiring. A big thanks to Martin for your help and advice which proved to be spot on. Also thanks to Bob for his contribution.] Inverter is up and running and everything seems fine. If any of you are going to Warwichshire in October I would love to buy you a pint!

Thanks Again

Paul

Glad I could help. I'll put a note in my diary for October! Martin