Star/Delta motor wiring

[.RC.]

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With my little TC grinder I finally bought a VFD for it so I can run it off 240V plus can run it faster for the smaller grinding wheels..

A plate on the side of the grinder gives directions for wiring for 208V or 415V, as well under the electrical plate on the motor gives directions for "high" voltage and "low" voltage..

However there are only three wires coming out of the motor to the terminal block...

I have pulled the motor apart and think I have found three wires twisted together.. I assume this is the centre point for the Wye winding and I will need to unsolder those wires and bring them out to the terminal block.. To wire in Delta...

Does that sound right?

http://img.photobucket.com/albums/v606/OzRinger/wiring20electric20motor20003.jpg

http://img.photobucket.com/albums/v606/OzRinger/wiring20electric20motor20012.jpg

[kwijibo99]

G'day RC,
That looks like it.
Best way to test is to dissconnect them then using you digital multimeter (I think that's one I see in your pic) measure the resistance between each wire and its partner terminal (the other end of each coil will be connected to one of the three terminals)
If that is the common point of the star then the reading should be the same for each coil (typically around 9 ohms for a 4 pole motor).
A handy tip to remove the shelac coating is to heat the end of the wire with a lighter to burn off the coating then give it a rub with steel wool.
Cheers,
Greg.

[Greg Q]

It depends...the terminal block may have nine terminals and some joiner links. The joiners are configured per the diagram.

[Jekyll and Hyde]

It depends...the terminal block may have nine terminals and some joiner links. The joiners are configured per the diagram.

But if there are only 3 wires coming out, wouldn't that suggest the motor is permanently wired in star config? In which case I would have thought that changing the joiner blocks around would cause some quantity of smoke to escape.

However, I will freely admit that I'm pretty fuzzy on the details of 3 phase and motors. I was under the impression that the change from star to delta was a requirement to get from 415v 3 phase to 240v 3 phase for some reason which I can't remember.... Hopefully I'll learn something new in this thread!




However there are only three wires coming out of the motor to the terminal block...

I have pulled the motor apart and think I have found three wires twisted together.. I assume this is the centre point for the Wye winding and I will need to unsolder those wires and bring them out to the terminal block.. To wire in Delta...


Your photo certainly looks like the star point I found in my mill motor, I'd agree with Kwijibo that you seem to have found it.

[Stustoys]

I dont understand the wiring diagram. It looks to me in be wired in star in "low voltage" and delta in "high voltage"(which as I understand it is backwards to most motors).................. anyone care to explain?

Stuart

p.s. how may hp is the motor RC?
p.p.s. what rpm?

[Graziano]

So there's only 3 external wires even though it has the sticker for a basic nine wire dual voltage motor?. If it was a nine wire you may have wires labelled according to the sticker internally which is what my Baldor had when I rewired it for lower voltage.

Otherwise that three wire connection must be the star connection and you can disconnect all three from each other and check with a multimeter on low ohms setting to get each of the three windings.

To get the lower voltage for a nine wire motor each phase has two windings and you end up with two sets of star connected, 3 phase windings in parallel. The stars are not connected together but the line connections are which is something I'd never seen before in a 3 phase motor.

So in a nine wire motor, you have two sets of 208V star windings each at half the total rated current which are then paralleled to give full rated motor power.

Edit: so for the windings you do have, you'll have to connect as "delta" to get 240V operation. Attached below is the nine wire arrangement I had with my Baldor 2Hp to get 230V operation.



http://www.woodworkforums.com/attachment.php?attachmentid=199205&stc=1&d=1329997054

[jhovel]

RC - that motor has been rewound. Nothing on the label or connection diagram is of relevance. At 208V it would have been made for Canada and maybe didn't survive running on 240V. When it was rewound, they saved some effort by wiring it for Australian common 415V 3-phase mains connection.
Joe

[.RC.]

I wonder if it is a typo or not...

The picture on the machine contradicts the picture on the terminal cover... I think the motor ia 1/3hp, 3000rpm so a single pole...

http://img.photobucket.com/albums/v606/OzRinger/wiring20electric20motor20007.jpg

[kwijibo99]

From what RC describes with only three wires coming out of the motor and the look of the yellow insulation I suspect this motor has been permanantly converted to 415 star winding at some stage after its manufacture.

A nine terminal motor is usually a star wound motor which can be configured to run on either a higher or lower 3 phase voltage (208 or 415 in the case of this motor) .
If the links are connected as per the low voltage configuration then only the three coils wound for the lower voltage will be connected to power. If the links are configured for high voltage then an additional coil is series connected to each segment so as to handle the higher voltage.

[.RC.]

I have pulled the wires apart, resistance is 21-22 ohms per winding

It may have been changed after manufacture... It is an ex-govt machine and I am the third owner, it has seen next to no use though..., perhaps it was incorrectly wired for 415V when new and when connected to 415V the magical smoke got released necessitating a rewind...

[RayG]

Hi .RC,

What I think you've got is as Graziano suggested is a nine wire dual voltage set up... but it might be irelevant if it's been rewired as Joe said for 415v star..

Seperate the star point and bring out the 3 wires, make sure to seperate and insulate securely.. you should find 3 sets of coils, with 3 wires per coil (if they are still there), the tapping on the windings can be ignored, and wire the outside tappings as delta. That should be 240V 3 phase.

I'll try and find the relevant diagrams in Rosenberg, hopefully that will make more sense..

ok here is the 9 wire dual voltage, this is probably what it was originally..

http://www.backsaw.net/pics/Misc/9wireStar.jpg



Regards
Ray

[.RC.]

Motor winding image

http://img.photobucket.com/albums/v606/OzRinger/antenna20010.jpg

[Graziano]

If there's only six wires, disagreeing with the label then it would have to have been rewound at some stage to give three sets of windings like JHovel and Kwijibo said.

The three internal wires would then make it star connected for 415V. All you can do at this stage is bring the six yellow wires out of the motor case and reassemble the motor, then connect the windings in delta form to get a 240V three phase motor.

You'll need to get some spaghetti tube from an electrical shop to cover the three extra wires/joins where you bring out the three wires from what was the original star connection, heatshrink or electricians tape is not really good enough due to vibrations, some sort of high temp woven electrical spaghetti slid over the top of some heatshrink over the soldered connection will do the trick. A non synthetic string like cotton string would be preferred to tie the joins to the windings as hot windings can melt synthetic strings or cable ties and make them let go when very hot like a temporary overload.

[jhovel]

I agree with Graziano. This is a 4 pole 1440rpm winding with just three sets of coils. You can (well, I can) see them all and their connections. Definitely 415V star (wye) wired. All you can do it split the 'centre' and bring those wires out to run it in delta on 240V off a VDS.
The beauty is that you found the centre point. SO it;s quite simple. My lathe motor is the same but I can't find the centre point..... it must be tucked under somewhere.
Joe

[Log]

Hi guys, new here.
Just mentioning :)
Hopefully, whoever rewound the motor has labeled the three wires that came out of the motor U1, V1, W1, (or alternately A, B, C) so that the winding sequence can be hooked up correctly. If they are labeled you will be able to identify U2, V2, W2 (or A1, B1, C1) so you can get the correct sequence.

If the sequence is wrong the current draw will be high.

If U1, V1, W1 are not labeled then a motor re-winder will be able to identify them for you.

For Delta connection, join U1 to W2; V1 to U2; W1 to V2. Connect each input line to each one of those pairs.
Alternative Delta connection is U1 to V2; V1 to W2; W1 to U2. Connect each input line to each one of those pairs.

Very good that the motor re-winder left the star point so easily accessible. :2tsup:

Cheers.

If I'm not right, then I'm wrong, I'll just go bend some more bananas.

[.RC.]

I got some Vinidex abrasion/heat resistant sleeving at Jaycar today, should be right to wire it up when I get some time now...

[RayG]

Hi .RC,

I could have got some for you earlier today, :) there is a special hi-dielectric heat resistant varnish they use in rewinding as well. It's not the sort of thing you need a lot of, but I don't think it comes in small containers. I could get some if you like.

Old wiring can be fragile, so make sure to double check everything. I know you will, but doesn't hurt to mention it anyway.

Regards
Ray

[.RC.]

Thanks Ray, I probably do not need any varnish at this stage...

Just one question, I have soldered the wires onto the windings wires, I guess putting heat shrink tubing over the top over the soldered joins and the heat resistant tubing over the top of that is not the way to go? And just use the heat resistant tubing on it's own?

The wiring on this grinder is OK... The machine was made in the 90's..

[RayG]

Hi RC,

You don't need heatshrink, the wire insulation is probably class 180 (rated to 180 C), the termination procedure is to push on the smaller diameter heat resistant tubing, nice fit to the wire, then cover with a piece of larger diameter tubing and tie it down neatly, make the splice nice and smooth and not too lumpy.. when you do the solder joint make sure you get the insulating varnish off the magnet wire, and tin the ends before joining and finally soldering.

EDIT.. when you tie it down, make it so the join isn't under strain.... that is tied both sides.... bit hard to describe in words, but I think you've got the idea.

Regards
Ray

[RayG]

Hi .RC,

One more thing...

For tying the cabling down, see if you can get some of the proper lacing cord.

Search for "stator lacing cord"

Regards
Ray

[.RC.]

I had a play this evening, but the mosquitos started to carry me outside so I left them to it...

It is probably satisfactory but I am not 100% happy with it in so far that the plastic coated hook up wire I used (recycled out of a modern washing machine so I know the insulation was rated for 240+V) is in contact with the windings for part of the way.... Although in saying that the existing windings that I never touched had the plastic coated hook up wire touching the windings anyway...

I tied it all up with cotton string, recycled out of a new seed bag... it is that string they use in the big sewing machines that sew up bags.... it is quite strong and would appear to be pure cotton...

How do I identify the U, W and V wires so it is hooked up correctly....

From looking at it the coil tappings are directly opposite from one another...So if you identify one wire, the other end of that coil is the wire that is directly opposite.. Of course the windings are spaced 120 degrees apart...

[RayG]

Hi RC,

Pick a wire and label it U1, using the multimeter find the other end of that coil and label it U2, pick the next wire around and label it V1, use the multimeter again to find the other end and label it V2, next one around label it W1, find the other end and label it W2.

If you have 6 terminals bring the wires out so that looking across the terminals the first row reads

U2 V2 W2

second row reads
V1 W1 U1

Now you can connect it as delta by connecting U2 to V1 ...V2 to W1 .. W2 to U1 by just linking straight across the terminal block to make it 240V delta.

Your three phase power U V W is connected to U1, V1, W1 as normal.

Regards
Ray

PS Cotton should be fine, not so sure about the PVC temperature rating, also I think it goes brittle over time, but it looks to be well supported..

[.RC.]

I need some clarification there please Ray...

I have identified each coil, where each coil is connected I just need to identify the U, V, and W points..

When you say "Pick a wire and label it U1, using the multimeter find the other end of that coil and label it U2, pick the next wire around and label it V1"

Do you mean exactly like that.... As shown in picture one... The first wire I pick is U1 then moving clockwise 60 degrees the next wire is V1 and move clockwise another 60 degrees and that wire is W1.

I am not sure if it matters but I was thinking if the coils are not wired correctly when it might not create the correct magnetic field with on say one of the fields the north/south are pointing the wrong way...


Or is it like in picture two... I find the wire U1, then move clockwise 120 degrees and find V1 and another 120 degrees and find W1.

With the corresponding U2, V2 and W2 directly opposite in both cases... To wire this motor to wye or star configuration it is like the second picture.. U2, V2 and W2 were out to the terminal block, while U1, V1 and W1 were joined together...

I have changed my wiring as well, it is now mostly covered with protective sleeving...

[Graziano]

RC, it's not at all critical which way it's wired except for two conditions:

1. Each of the wires is connected together with a wire from a different winding and then to a line phase. So you have three pairs of two winding wires connected together, and each of the pairs is connected to a line phase.

2. If it runs backwards then swap the wires of one winding only.

It's pretty much as you have labelled the wires in your photos either one would work fine.

[RayG]

Hi RC,

I would do it like the fist picture, the north south alternating is done when the motor is wound, that is alternating polarity every second pole. If you swap the windings over it will just run backwards... :)

Here's a better diagram of a 3 phase 4 pole motor. This is from Rosenberg. Note that he is labelling the windings anti-clockwise, but that doesn't make any difference.

http://www.backsaw.net/pics/Misc/3phase_motor.jpg

So, I hope that clarifies the issue... wire it up like your first picture, if it runs backwards, swap 2 phases, (pick any two).

Bring all six wires out to the terminal block so that you can choose star or delta at the terminal block, as already discussed. If you had a megger tester, this would be a good time to megger test the insulation.

In the absence of a megger, I would still double check that you don't have any shorts between any of the windings and ground, and no shorts between windings.

Regards
Ray

[.RC.]

Hi Ray, This is a two pole motor it runs at 2900rpm, I assume that makes no difference in the photo's you posted, except it has half the number of windings...

[Log]

An amp meter on each of your input lines will show if any phase is drawing too much current. Only run for max of a few seconds if one of the amp meters is reading substantially higher current. If incorrect connections then you have to go through connecting them in a planned change over sequence until you get all meters reading much the same.

Cheers

If I'm not right, then I'm wrong, I'll just go bend some more bananas.

[Log]

I've just sketched out a windings connection test sequence and scanned it so if you have any problem I'll post it up. Important to get the windings ends connected properly, changing the supply lines(L1, L2, L3) around doesn't change the windings ends connections.

Cheers.

If I'm not right, then I'm wrong, I'll just go bend some more bananas.

[.RC.]

Success gentlemen..... Works like a beauty....

[Graziano]

Success gentlemen..... Works like a beauty....


Awesome, your work looked well done and now with another skill under your belt, you can keep an eye out for a secondhand Kyoritsu megger unit for future motor projects.

[RayG]

Hi .RC,

Good to hear it works ok :2tsup: What machine is it going on?

A clamp meter with AC/DC current ranges is something else you'd find useful as well.

Regards
Ray

[Log]

Success gentlemen..... Works like a beauty....

Hi,
Motor's done and dusted, great stuff:clap2:
So when your not chasing cows:U or hiding from mosquitoes :Cyou'll be getting progress on the tool and cutter grinder eh :D, that's good :2tsup:.

I see here and there that you have a Chin Hung lathe, nice machine, I have similar older one, year 2004, 430 x 1100, but am missing the thread cutting dial assembly :cry3:. Don't really need it as I just keep the 1/2 nuts closed throughout the threading job. Wouldn't mind though some close up pics of one and any pertinent information for when I get the urge :doh: to fabricate one. My leadscrew is 6mm, am guesstimating that yours is the same so am thinking the dial has 15 lines, that's what my sortofenglish:rolleyes: manual shows.

No urgency, just if/when you get a chance to...

Cheers.

If I'm not right, then I'm wrong, I'll just go bend some more bananas.

[.RC.]

The VFD is going on the small TC grinder, mainly so I can run it off 240V, plus also I can vary the speed to suit different wheels...

Log, my Chin Hung is an inch based machine and has a 4tpi leadscrew.... It was specially ordered like that.... They are damn nice lathes wouldn't you say.... I really really like mine...

I have the instruction manual if you need a copy...

[Log]

Log, my Chin Hung is an inch based machine and has a 4tpi leadscrew.... It was specially ordered like that.... They are damn nice lathes wouldn't you say.... I really really like mine...

I have the instruction manual if you need a copy...

Yes very nice machines, wish mine was new. Only had mine a number of months, obviously bought second hand so had no choice of leadscrew.
Thanks for the offer on the manual but I have one which also has major component drawings and spare parts lists.

The manual I have belongs to this machine but there are variations etc, plus it's obvious that there were some design changes in places and the manual covers various models within that family range.

The DRO display wasn't with it and the scales are stuffed, I pulled them off the other day and now have new scales in hand. Am going to use an "Easson ES-10 Lathe" display that I have had for a few years now, it was on another machine.
I also have a soft start to fit to stop the instantaneous jar on start, which does affect the cross slide a bit, should get a chance to fit it some time next week.

The cross feed dial is marked for diameter and each division is .04mm which is a bit of a pain to say the least because it's a chore to work out:rolleyes:; fer instance, say how many divisions to move to take off 1.75mm etc etc etc. Some may be able to but I can't do those sorts of calculations in my head so am looking forward to getting the scales and display fitted up.

Yes nice lathe indeed, hardened long and cross slides, oil bath cross feed screw, auto or manual oiled saddle long and cross slideways. You have filled your cross feed screw reservoir,, yes?,,:U. Coolant will probably eventually find it's way in there so I will suck mine out periodically if required and refill.

Cheers.

If I'm not right, then I'm wrong, I'll just go bend some more bananas.