3 phase motor connection type???

[LEO]

Hi Guys,


I am now working in a industrial environment as an Electrician having spent the majority in a domestic or commercial environment, I have done installation work with 400v 3 Phase however I am a bit rusty on the STAR / DELTA 'meaning' on the id plate of the motor. What my question is... Does the rated voltage imprinted on the id plate of the motor mean 'what the voltage of the windings are rated at in either a STAR or DELTA connection' OR is it' what we look at (on id plate) and wire the motor up in acorrding to the line voltage present'?

Hope this makes sense, any comments to help clarify this would be great.

Many Thanks, LEO.

 

[johnboy6083]

nowadays, if the motor is started via an inverter, then its likely to be wired in delta. if the rating plate says delta 400v and say star 230, the if you want it to run on 400v, then you link it out in delta.

 

[Knobhead]

View attachment 5878
Delta
View attachment 5879
Star

Depending on the motor design some will be rated 400V Delta. These can be used with star / delta starters. Dual voltage motors can run a 230V Delta, 400V Star.

 

[silva.foxx]

VFD - PT KANIA look at Step 2.

Industrial Knowledge: Reading A Motor Name Plate

Useful?

.

 

[LEO]

Hi,

Thankyou for your responses. I'm still a little unclear, I know how to connect them up in star or delta etc, but still what I am unclear on is what the meaning of the voltage figure is on the id plate of the motor, is it what voltage the windings require to run in the star or delta connection to optimum performance or is it what my line voltage across phases need to be at the supply to the motor, i have seen some odd figrues eg. 380v, 690v, 220v etc.

Basically if I have a normal 3 phase 400v supply (across phases or 230v to earth on each phase) to a motor, how do I tell whether I need to connect it in star or delta?

Thanks again guys.

 

[Knobhead]

Have you looked at the links Silva has given?
View attachment 5899

It's all on there.

690 star 400 delta

380 regard as 400
220 regard as 230

 

[LEO]

Thanks, yeah I did see silvia's link it was very helpful - thanks silvia.

I think I'm possibly thinking to much into this?? basically if I've got a 3phase 400v supply + I fit the motor, I just connect it up in whichever of the one types of connection (star or delta) has 400v by it?

Hopefully this is the case, and the odd figures were making it slightly more unclear to me... I've also seen 660-720v in star? Would this only be achieved through a inverter or drive I presume?

Cheers,

LEO.

 

[silva.foxx]

...basically if I've got a 3phase 400v supply + I fit the motor, I just connect it up in whichever of the one types of connection (star or delta) has 400v by it?

Hopefully this is the case...QUOTE]

Spot-on, Lea (and don't call me silvia)

230v Delta is basically what you connect as if connected to a single phase inverter (single phase in - 3ph out) as you'll only get out of the inverter the max of what you put in. So from a 3ph inverter you can get your 400v out (basically).

 

[LEO]

Ha ha, sorry Silva...

Thanks for the info guys.

So where would I get the 690v from to connect it in star? If it's a 3 phase 400v supply, or I take it this would be the incorrect type of motor or the Delta config would suit at 400v??

In a application where the motor had to be connected in star at say 690v as stated on the id plate, where/how would you achieve this?

Sorry to go on but would like to know as much as poss.

Cheers, Leo.

 

[pmac10]

this is a good question silvia, and one i should know, but where do you get a 690V supply? i've seen motors and drives marked with this and been told but forgotten.

 

[Knobhead]

I’ve worked on 660V & 550V systems. Where you are just dealing with motors and not bothered about Fred needing 230V for his kettle, higher voltages mean smaller cables. OK if you needed 230V you had to put in a small transformer.

Every plant I worked on as an apprentice was 550V. I was involved with installing a new plant, it had got this weird voltage 433V! Some of the old guys didn’t know what to make of it, 230V without a transformer??? Just to add to the fun, after a few years the systems expanded so some areas had both 433 & 550 side by side.

Think about it, a 200A feed at:
433V = 150KVA
550V = 190KVA
660V = 230KVA
They all use the same grade of cable

 

[micknew]

This thread has been puzzling me.
Just realised that the live rail on railway is said to be 690V, so most of us will never come across a motor with that spec.
Also 230V 3 phase is a continental system.
A dual voltage 3 phase motor rated at 230V 3 phase would have to be connected in delta and at 400V would have to be connected in star.

 

[pmac10]

Tony, were those voltages (550.660V), at the secondary of an 11kv transformer supplying your site/plant? did it have to be further transformed to 400v? now i'm confused (easily achievable)

 

[Knobhead]

This thread has been puzzling me.
Just realised that the live rail on railway is said to be 690V, so most of us will never come across a motor with that spec.
Also 230V 3 phase is a continental system.
A dual voltage 3 phase motor rated at 230V 3 phase would have to be connected in delta and at 400V would have to be connected in star.

The 3rd rail is DC.
230V is as you say a continental / American system so dual voltage motors quite neatly get around the problem.

 

[Knobhead]

Tony, were those voltages (550.660V), at the secondary of an 11kv transformer supplying your site/plant? did it have to be further transformed to 400v? now i'm confused (easily achievable)

Yes the supplies were from 11KV transformers. Nearly 50 of them, ranging from 250KVA to 1800KVA fed from 14 of our own substations.

Just to confuse you even more if say we needed 230V for an office block we would install a 550/230 3Ph transformer. 230 between phases, 133 to the star point.

When we started to install 433V transformers I thought it was great. A neutral that you could use, no faffing about with 230V transformers. The old boys didn’t like it, they just couldn’t get their heads around it. One of the old duffers installed a new 230V board, it had got a neutral bar instead of two banks of fuses! What does he do? Connects phase to the bar and neutral to the fuses! Then have a guess which fool went to connect a new load to the board, I was flat on my back after touching the neutral!