Motor rating plate

[ΩΩΩ]

Been reading up on DOL starters, as needed for AM2.

I have a couple of questions please. For motors less than 4kW

Can a DOL starter be used for a star connected motor and a Delta connected motor?

Why would you chose one over the other. ( I know a little about the start up currents, and the start delta starter) This is particular to the DOL

Looking at some rating plates you get the following U220-240 D / 380-415 Y
This confuses me, as I would have thought the 320-415V would be delta and the 220 - 240 would be Star, as you have a 230 connection in star.
I thought delta was 400v? Poor misunderstanding on my part

Any help would be great, thanks

 

[JohnW2]

Looking at some rating plates you get the following U220-240 D / 380-415 Y
This confuses me, as I would have thought the 320-415V would be delta and the 220 - 240 would be Star, as you have a 230 connection in star.
I thought delta was 400v? Poor misunderstanding on my part

I think we 'know what they mean', don't we? A 3-phase supply with 220V phase-neutral would have about 380V between-phases, and with 240V phase-neutral would have about 415V between-phases (and, as you say,230V phase-neutral would be about 400V between-phases). It's the 'star' and 'delta' which is confused/confusing.

Kind Regards, John

 

[ΩΩΩ]

Don't think I've explained myself very well. So if we had voltages of 230V and 400V

Ive basically got no understanding of motors

We have L1 L2 and L3 coming into the motor all at 230 V
Each phase is 230V and if we go between them its 400
We have U1 V1 W1
And W2 U2 V2

Star is
U1 V1 W1

W2 --U2-- V2

Delta

U1 V1 W1
I I I
W2 U2 V2

So what voltage do we have between the windings?

Thanks for answering

 

[JohnW2]

Don't think I've explained myself very well. So if we had voltages of 230V and 400V ... Ive basically got no understanding of motors
... We have L1 L2 and L3 coming into the motor all at 230 V

yes, all 230V relative to 'notional neutral'.

Each phase is 230V and if we go between them its 400

again, yes, each 230V relative to 'notional neutral', with 400V between any two of them.

We have U1 V1 W1
And W2 U2 V2
Star is
U1 V1 W1
W2 --U2-- V2
Delta
U1 V1 W1
I I I
W2 U2 V2
So what voltage do we have between the windings?

I'm not sure I understand what you are depicting. However .....

With 'star' connection of the windings, one end of each of the three windings will be connected together at the notional 'neutral' point, with the other ends of each winding connected to one of the phases of the supply. There will therefore be 230V across each winding.

With 'delta' connection, the three windings will be connected together in a 'ring', with each of the three 'connection points' connected to one of the phases of the supply. There will therefore be 400V across each winding.

Does that help?

 

[ΩΩΩ]

Thank you, I think I understand that but it brings me back to the U220-240 D / 380-415 Y (simplified) U 230 D / 400 Y
What you say suggests to me that D should be 400 and Y 230

 

[JohnW2]

Thank you, I think I understand that but it brings me back to the U220-240 D / 380-415 Y (simplified) U 230 D / 400 Y
What you say suggests to me that D should be 400 and Y 230

Unless we are both 'missing something', I agree. As I wrote:

I think we 'know what they mean'.... It's the 'star' and 'delta' which is confused/confusing.

Kind Regards, John

 

[RandomGrinch]

Thank you, I think I understand that but it brings me back to the U220-240 D / 380-415 Y (simplified) U 230 D / 400 Y

I believe it is the voltage required through the windings, in that particular configuration, to achieve the rated power of the motor...

 

[JohnW2]

I believe it is the voltage required through the windings, in that particular configuration, to achieve the rated power of the motor...

Whilst that is mathematically true, I struggle to see of what practical relevance it is, since, with a standard 3-phase supply, the option of "380 - 415V across each winding" in 'star' configuration does not exist.

It is probably more meaningful to say that, for a given 3-phase supply (hence particular phase-neutral and phase-phase voltages), the pwower will be three times greater when wired in 'delta' than when wired in 'star'?

...or am I getting it all wrong?

Kind Regards, John

 

[plugwash]

I would interpret it as the motor rating plate is telling you how to wire up the motor depending on the supply you have.

Three phase supplies are normally quoted by the voltage between phases. If you have a supply with 400V between phases you should wire it up in Star. If you have a supply with 230V between phases you should wire it up in Delta.

Supplies with 230V between phases are basically unheard of in the UK, but I believe they are sometimes encountered in other parts of Europe.

 

[JohnW2]

Three phase supplies are normally quoted by the voltage between phases. If you have a supply with 400V between phases you should wire it up in Star. If you have a supply with 230V between phases you should wire it up in Delta.

I agree - but as I implied (for UK), and as you go on to say

Supplies with 230V between phases are basically unheard of in the UK, but I believe they are sometimes encountered in other parts of Europe.

Perhaps, but I've personally have never heard of them in any country.

As far as the rating plate is concerned, I think I'll stick with what I originally wrote, namely ....

.... It's the 'star' and 'delta' which is confused/confusing.

... since I don't really think it is very clear (certainly not to me, or the OP) what they are trying to say.

Kind Regards, John

 

[333rocky333]

Both star and delta motors usually require 3 phase 400v between phases.
Therefore a 3ph DOL starter can switch either as it is just making all 3 phases and maybe providing overload protection.
Delta would be normally used for larger motors but likely then need star to get them moving.
As the 3 windings are balanced, in UK I don't recall ever seing a N connected within the 3 phase motor, it would be catastrophic if a star delta starter was in use.
Check the drawings you look at are UK,
It may be some 3 winding motors can be somehow linked out maybe to run from single phase with just L and N usually involving a capicitor

 

[JohnW2]

Both star and delta motors usually require 3 phase 400v between phases.

Indeed - so what do you think that plate is trying to say?

Is it merely trying to make the (obvious) point that a 3-phase supply which has "400V between phases" (which is what it will get in the UK) is one in which each of the phases is 230V to notional neutral? If so, I'm not surprised that the OP was confused by the way it is written.

Kind Regards, John

 

[JohnW2]

Both star and delta motors usually require 3 phase 400v between phases.
Therefore a 3ph DOL starter can switch either as it is just making all 3 phases and maybe providing overload protection.

Indeed, as you imply, a DOL starter is simply a 3-pole switch, with or without associated overload protection.

I'm not sure why there would ever be a 3-phase motor permanently wired as 'star', since it would be about 3 times less powerful than it would be if it could be used in 'delta' configuration [or, put another way, a much smaller motor would be 'as powerful' if always used in delta configuration]. Am I missing something?

Delta would be normally used for larger motors but likely then need star to get them moving.

I think that statement could confuse people, since it could be read as meaning that it requires 'more power to get it mowing' than would be available in delta configuration - whereas the fact is, of course, that there is about 3 times more power when used 'delta'. As I understand it (as always, perhaps incorrectly!), the reason for "star-delta starters' is that large motoirs can draw very high starting currents, so better to start them, 'at lower power, in star, before switching to delta 'when they have got going'.

Rather than by using a 'star-delta starter' the same could theoretically be achieved by having the motor always in delta configuration but start it it with a hypothetical '230v between phases' supply (which certainly does not exist in UK) before switching to the usual '400V between phases' one after it got started.

KInd Regards, John

 

[ΩΩΩ]

Decoding your motor’s nameplate | Plant Engineering

The most relevant information of a motor should be recorded on the nameplate, which includes frame size, voltage, power and more.

www.plantengineering.com

Where there is more than one voltage figure listed, the delta (△) connection is the lo-voltage connection, while the star (Ｙ) configuration is for a high-voltage connection. The wiring diagram for both delta and star configurations will often also be added to the nameplate.

 

[ΩΩΩ]