Thread: First star to delta conversion

Hi all,

I'm prepping to do my first 3ph motor star to delta conversion. I saw it done last year when a kind forum member helped with an old Hercus hacksaw motor, and after some vids and research, I reckon I can give it a go myself. I am a sense-confessed, fully-paid, card-carrying electrical dunce. It's not my strong point. I still need to get some raw materials like the appropriate wire to extend stuff (with heat resistant shielding).

The candidate motor is some good Aussie kit. This guy - it is star only at the moment:

IMG_20200616_184138.jpgIMG_20200616_184929.jpg

I have a question:

There is a 4th wire in there labelled as 'N' (Neutral I guess). I'm not sure how that fits into the Delta picture and what it should be connected to when all is done - if anything. Any hints?

IMG_20200617_125814.jpgIMG_20200617_125932.jpg

Many thanks,

Greg.

That N wire is connected to the star point. Essentially it goes away when you do the delta conversion.
You find where that connects to the 3 windings, separate them, then you need to connect the "star end" of the L1 winding to L2, star end of L2 to L3, then the star end of L3 to L1.

Steve

Thanks Steve - appreciated. I had a suspicion that it became redundant in delta. So, just leave as unconnected to anything? (with sealed ends).

I am guessing if anybody wanted to reconfigure as star, then they'd need to take this into account.

You do realize that motor is already star connected? And why would you want to convert a 415V delta to star conversion? That would make it a 690V motor.

I'm wondering the same thing BobL.

Originally Posted by BobL

You do realize that motor is already star connected? And why would you want to convert a 415V star to delta conversion? That would make it a 690V motor.

I think you have your star and delta mixed up.

415V Star converted to Delta and it is now 240V as per here

Originally Posted by BobL

A 240V 3P Motor can run from a VFD in either ∆ or Y mode, BUT it has to be set up for not just "∆ or Y but "240V ∆" or "240V Y".

It just so happens that if a 440-415V Y is converted to ∆ becomes a 240V ∆ and VV
However, if a 440-415V ∆ is converted to Y it becomes a 690V Y and VV

You can of course run a 440V Y or ∆ from 240V 3P without any conversion and it will deliver somewhat less that half its rated power.
This seems to work better on some motors and not so well on others.

The only way to get full power is to have it rewired.

Thanks all,

Just showing how little I know here. My apologies.

My understanding was a 415v star motor converted to delta config enables it to run as 240v three phase using a 240v VFD. On other motors I have the connector box has the ability to reconfigure the 415 star to run as 240v delta. Not this one.

Do I have that wrong? .. or am I using the wrong terminology?

Apologies again - like I said - not my strong point ...

Greg.

EDIT: Bobl: when I said "I am guessing if anybody wanted to reconfigure as star, then they'd need to take this into account." .. I was meaning _after_ I had done this, if anybody wanted to undo the delta and make it star again.

Stray, you might want one of these https://www.aliexpress.com/item/4000...archweb201603_

OK I understand now.

Shed, I didn't even know such a thing existed to be honest. Is that real then? Does power drop to half or something?

But, I have a 240v VFD already that'll do the job if this thing was 240v 3 phase. And I'm not sure anybody want to wait for goods from China! Maybe that is better now.

BobL: thanks - it is a very dangerous thing me talking about electricity - especially to people who actually _know_ what they are talking about! - my brain gets most things, but there is something about electrics that just doesn't ever sink in .... like the million requests to not leave my socks on the floor ....

Originally Posted by StrayAlien

Thanks all,

Just showing how little I know here. My apologies.

My understanding was a 415v star motor converted to delta config enables it to run as 240v three phase using a 240v VFD. On other motors I have the connector box has the ability to reconfigure the 415 star to run as 240v delta. Not this one.

Do I have that wrong? .. or am I using the wrong terminology?

Apologies again - like I said - not my strong point ...

Greg.

EDIT: Bobl: when I said "I am guessing if anybody wanted to reconfigure as star, then they'd need to take this into account." .. I was meaning _after_ I had done this, if anybody wanted to undo the delta and make it star again.

Pretty confident you've got it right. 415v star becomes 230v delta. Both have 230v across each winding.
Remove that wire - no point in having it in there. Extend the other ends of the windings out to the terminal block and you'll be able to set it up like a normal dual config motor so that it can just be jumpered at the terminal block.

Steve

Originally Posted by OxxAndBert

Pretty confident you've got it right. 415v star becomes 230v delta. Both have 230v across each winding.
Remove that wire - no point in having it in there.

I have a motor identical to that one that I converted. I wouldn't remove that grey wire - pull the grey insulation off and your should see 3 wires (start point) which are the other ends of the 3 coils. Separate these wires out and they should show continuity with the red(R), Yellow(Y) and brown(B) wires.

Then you may need to extend the separated wires and mark the one continuous with the red wire as R1, same for the other two, B1 and Y1.

Then connect Y1 to R on its terminal, R1 with B on its terminal, and R1 with Y. Then the 3 phases on top of each of those.

Ace. Thank you. That gives me a lot of confidence.

Thank you all. I'll post back my success story .. hopefully!

I really appreciated the advice and wisdom.

Thank you again all.

Greg.

I found a photo of my motor.
motor.jpg

Nice! Is the red arrow significant?