Wiring a star delta pump DOL

[TomS]

Hello all. Odd question but can you wire a Star Delta motor (flying 7 core lead) into a DOL starter/contactor?

 

[ProDave]

Look up "stat delta starter"

Are you talking about wiring it delta and just hoping?
 

 

[TomS]

7 core - so 6  cores (3 for U1,V1,W1 and 3 for U2, V2, W2) and 1 core for earth presumably ?

Yes you can wire the 6 cores to a 3 wire DOL (either 3 wire delta or 3 wire star depending on the voltages)

So bell out the pairs I.e U1-U2, V1-V2 and W1-W2 and make them off in pairs into the DOL 3 phase starter/terminals?

 

[TomS]

Not as simple as that, and if the 1's and 2's are not marked you'll be stuffed. And they may be marked up X,Y,Z or A,B,C etc U1 and V2 etc was an example.

It also depends if you need to run the motor in star or delta (probably delta - but without seeing the motor/nameplate its hard to be 100% correct)

It will be in delta I believe. Cables numbered 1-7. So I can't just bell them out? this will get messy.

 

[Sidewinder]

You can bell them out to find out which pair goes to which winding and label them anyway you like, e.g. for windings U, V & W.

However, you will then need to find which is the start and end of the winding, i.e. the 1 & 2 that Canoeboy refers to.

 

[TomS]

You can bell them out to find out which pair goes to which winding and label them anyway you like, e.g. for windings U, V & W.

However, you will then need to find which is the start and end of the winding, i.e. the 1 & 2 that Canoeboy refers to.

So assuming the 1,2,3 are 1s and 4,5,6 are the 2s would they then need to be paired and made off? i.e 1 & 4 together in a terminal and 2 & 5 together and so on?

 

[Sidewinder]

IF, and it is a BIG IF, the relationship is as follows:

1 - U1

2 - V1

3 - W1

4 - U2

5 - V2

6 - W2

Then you would need to connect them in either star or delta as you wanted, so yes you would connect them appropriately.

Given the info above, which may be nothing like you have, how would you connect them in Y or D.

Have you looked in the motor TB?

 

[Evans Electric]

You could be in trouble with that , I believe  TomS .  You need to identify windings a, b & c   but then you don't know which end is which  , which can cause a problem If I remember right .    

I went to reconnect a heating pump once , a row of 6 pumps , one had failed and a replacement was fitted.  

The links were not fitted in the connection box so I think Ah!  is it star or delta .     I am being pressured to get it running so I look at the other 5 pumps in the row , all connected in delta , DOL  IIRC  so I link new one the same and it melts .  :C   

 

[Tony S]

So assuming the 1,2,3 are 1s and 4,5,6 are the 2s would they then need to be paired and made off? i.e 1 & 4 together in a terminal and 2 & 5 together and so on?

If and only if the pairs are as you say

For star connect 1, 2 and 3 to the starter line outputs, short 4, 5 and 6 together.

Delta connect 1&5, 2&6, 3&4 to the starter line outputs.

If one of the windings is reversed end to end there’s a test method here:

https://talk.electricianforum.co.uk/knowledgebase/electric-motors-and-generators/testing/motor-testing-r12/

 

[apprentice87]

Ok, all the above was as clear as mud to me!!

Once you have found the ends of each pair of windings they go in a terminal box as shown here;

View attachment 7670

If you call one end of the windings "1" [the starts] and the other end "2" [the finishes] Connect the "2's" to the top row and the "1's" to the bottom row

Then link them as in this diagram below and connect the incoming supply from the DOL starter to 1, 2, and 3,

You motor is now in delta

View attachment 7671

All this assumes that you have correctly identified the "starts" and " finishes"

If you have not, god knows what will happen!! [but one of the forum members will know!!] I would assume that the motor would not start and draw lots of current!!!

john...

 

[Tony S]

The way the pump is described it has no terminal box

 

[apprentice87]

What i meant was to bring the wires out and imagine there was one, to make understanding what goes where easier!

Would this work or is it plain wrong...

I have been faced with this problem before with a 3 phase 380vac squirel cage motor where I received the motor back from the winders with just the six wires coming out and I had to fit the terminal block. You can solve the problem in a couple of easy steps.

1. Identify the three seperate windings with the aid of your multi-meter on the ohms range.

2. Once you have identified the windings mark the tails of each winding as follows :- winding 1 - U1 & U2 winding 2 - V1 & V2 winding 3 - W1 & W2

3. Now connect the three windings in series i.e. wire U2 to wire V1 and wire V2 to W1.

4. Connect a single phase supply (220vac) to the windings i.e. Live to wire U1 and Neutral to wire W2.

5. Switch on the single phase power to the windings and with your multi-meter measure the volt drop across the following U1 & U2, V1 & V2, W1 & W2. You will be able to see that two windings have the same volt drop and the third is different. Reverse the connections of the winding with the different reading and re-test. All three windings should now have the same volt drop.

6. Switch off the 220v power and now re-mark the coil ends from the start of the series connection you have made as U1 start & U1 finish, V1 start & V1 finish, W1 start & W1 finish.

7. Now first disconnect the three coils and then connect the windings as follows :-

U1 finish connect to V1 start

V1 finish connect to W1 start

W1 finish connect to U1 start

The windings are now connected in Delta

8. With your multi-meter on ohms check the resistance between each of the three wires marked start (U1 to V1, U1 to W1 & V1 to W1). The resistance read should be equal.

9. You are now ready to run the motor by connecting your three phase supply to U1 start, V1 start & W1 start.

10. Check the current on each of the three supply lines to the motor - they should be equal. If they aren't there is a problem and you need to recheck.

I hope this helps you out of your predicament.

john..

 

[apprentice87]

Actually had time to read the above now!! Would not fancy connecting up 240V in the way described.... Cannot see the winding being very pleased at all... Maybe a daft idea...

Still, there we are!!

john..

 

[Lurch]

You will be able to see that two windings have the same volt drop and the third is different

Really?

If all 3 are in series then measuring the volt drop will yield the same results no matter which way round the start/end of the windings are connected.

 

[Tony S]

Actually had time to read the above now!! Would not fancy connecting up 240V in the way described.... Cannot see the winding being very pleased at all... Maybe a daft idea...

Still, there we are!!

john..

It actually has a use for keeping motors warm when shut down.

Something I’ve got to add to knowledgebase.

 

[apprentice87]

Hi Tony, Yes, i read something years ago about the sort of thing you are on about when drying out motors that had low IR due to being stood unused for ages

Hi Lurch, Yes that is what i thought. I think what the person that wrote the thing was trying to do, was to explain this sort of thing, only not explaining it very well..

"First confirm U, V and W windings, by doing continuity test. Then follow the procedure given below.

1.Connect V and W windings in series.

2.Connect 110V/230V AC to U winding. In this case let us consider 230V is applied to U winding terminals.

3. Measure the voltage between V and W series circuit. If the meter reads about 460V, then opposite polarities are connected at the junction of V and W winding (V2 and W1 or V1 and W2)

4. If the meter reads about 0V. Then same polarities are connected at the junction of V and W winding (V1 and W1 or V2 and W2)

Repeat the same procedure to find U1 and U2 also.

But do it safely without touching any terminals during applied voltage."

I "think" what they are getting at, is, that if you join two windings in series, and apply power at one end and to the junction of the two windings, [in the middle if you like] you will, in effect, have made an autotransformer of sorts and by measuring the voltage across the pair of them you will then know the orientation of the second winding. [I think!!]

I have a motor here i can experiment on, might have a go and see what happens..!!!

john..

 

[Tony S]

Have a look at the link I posted earlier.

 

[Marvo]

We just use a 12 volt battery across one winding whilst there's an analogue DC ammeter that can measure low miliamps connected to another. You adjust the zero point of the needle using the calibration screw on the front of the meter so the needle sits somewhere above the zero then tap the winding wires momentarily onto the battery and note which way the needle makes a small deflection. Repeat with other windings and reverse them accordingly until the meter deflects the same direction regardless which winding the meter and battery are on. 

 

[bluetobits]

We just use a 12 volt battery across one winding whilst there's an analogue DC ammeter that can measure low miliamps connected to another. You adjust the zero point of the needle using the calibration screw on the front of the meter so the needle sits somewhere above the zero then tap the winding wires momentarily onto the battery and note which way the needle makes a small deflection. Repeat with other windings and reverse them accordingly until the meter deflects the same direction regardless which winding the meter and battery are on. 

Am i right in thinking this is also achievable with an LED if you don't have an analogue meter? 

 

[Marvo]

Am i right in thinking this is also achievable with an LED if you don't have an analogue meter? 

It's an interesting thought. It's something I've never seen done that way but in theory it could work with an LED although some may be more suitable than others due to forward volt drop requirements. I was shown this method durng my apprenticeship at which time it was much easier to lay your hands on an analogue galvanometer than an LED. Maybe give it a try and let us know.