9 wire 3 phase motor wiring
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Thread: 9 wire 3 phase motor wiring

1. Junior Member
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Jul 2007
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I have a friend who has a milling machine with a delco motor that has 9 wires coming off of the windings that were cut short before he got the machine. How can I find out which wires are considered which number off of the windings? He is going to run it low voltage 3 phase, which it shows that it can be wired for either High or Low Voltage. Thanks,Dean

2. Titanium
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You might do a search for this online. I did this a few months ago. You will need to identify Y or Delta wiring and group wires in 3s by checking continuity of all wires. Once they are grouped, you can measure resistance on each group to find, say the corner of the Delta. Once the corners are found, you have to use inductive kick testing to find which wire is exactly which.

After all this is found, you power up the motor and determine, by the rotation, which is actually T1,2,3. You can also take the motor apart to determine proper sequence but I think you still have to perform kick testing to get it all firmed up. Will take about 30min to do all of this once you understand how.

3. Nine wires will most probably be Y.

From outside to in, clockwise, is T1, T2, T3, T7, T8, T9, T4, T5, T6.

The "Y point", which otherwise would have been T10, T11, T12, is not brought out.

Line connections are always to T1, T2, T3, but also T4, T5, T6 for low voltage.

For high voltage, T4-T7, T5-T8, T6-T9.

For low voltage, also T7-T8-T9, forming a secondary Y point.

4. Junior Member
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There is a plate for wiring it for Low or High Voltage, For Low Voltage it says to join T1,T7 and T8 together to make Line 1 if I remember correctly, so that would be Delta right? I did try to find some info on line for the Delco model B-616 7-1/2HP motor to no avail. It is in a Kearney Trecker Milwaukee H Model Milling Machine. What is Kick Testing? I am not familiar with this term as I don't really work on this kind of thing normally. Thanks Guys!

5. Titanium
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You will not find much under a specific motor. All three phase motors will be the same as far as re-assigning the leads. Just shop for general three phase motor stuff. The make of the mill, or even the motor is irrelevant.

6. Low voltage ...

L1---1--6--7

L2---2--4--8

L3---3--5--9

High voltage ...

L1---1 4--7

L2---2 5--8

L3---3 6--9

7. Junior Member
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I tried to find something that would show how to determine which wires are considered what number off of the stator but could not come up with anything. The motor that I have does not have any markings on the wires at all! Hence my problem. I do understand all of the wiring directions as far as what goes to what, But I need numbers on the winding wires to do it and they are not there!

8. Cast Iron
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Feb 2004
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Kiron IA USA
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If there are no markings, it will involve some guessing. With an ohm meter, test all leads for continuity to the motor frame. There shouldn't be any. Then find 3 leads that have continuity. This is the internal star. Mark each of those wires A-B-C. Then with the ohm meter, find three pairs that have continuity. Mark each of those pair 1, pair 2 and pair 3. Use 2 colors to mark each of the 1-2-3 wires to denote different end of the winding. Then, you will have to get the motor to start by putting power to A B C. It probably won't start by it self, it will have to be spun. But you won't know which way. Once you get it going, then it is a matter of adding two of the other pairs, at a time to see if performance improves. But you don't know which end of the winding you are hooking up.There will be lots of combinations, write each one down so you keep trying different combinations. Once you get two, then it is just a matter of finding which way to hook the last one. The idea is to get all 6 windings pulling and in the same direction. Be careful, don't shock yourself.
The basic wiring diagram is 1-7 to one phase, 2-8 to second phase, 3-9 to third phase and 4-5-6 hooked together to be the external star. be careful. Don't get shocked.

9. "Then find 3 leads that have continuity. This is the internal star."

It's a ∆ motor, not a Y.

The generalized approach uses a combination of dc tests (simple continuity) and ac tests (transformation ratios) to discover which windings are related to each other winding, and their polarities.

A filament transformer, 120:6.3 volts, would prove useful as a source of safe ac.

A small control transformer, 120:24 volts, would be better.

10. Aluminum
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May 2007
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SE Pa.
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64
Three phase motor wire connections
First read the nameplate for wiring instructions. They are some times located in the “peckerhead” or junction box on the motor. If needed refer to the information below.
Determining wye or delta connection for motors
On delta connected motor lead #s (7,8, & 9), (1& 4), (5& 2), (3& 6) have continuity with each other
On wye connected motors (1,4& 9), (3,6 & 8), (7,2 & 5) have continuity with each other.

Wiring dual voltage wye connected motors
Low voltage L1=1&7, L2=2&8, L3=3&9, Join 4,5&6
High voltageL1=1, L2=2, L3=3 join 4&7, 5&8, 6&9
Wiring dual voltage delta connected motors
Low voltage L1=1,6,7 L2= 2,4&8 L3=3,5&9
High voltageL1=1, L2=2, L3=3 join 4&7, 5&8, 6&9

Delta connected motor, not wired, no lead markings;
Group each lead with the others to which it has continuity. Pay no attention to the very slight readings on the ohm meter as that is continuity thru the windings.Leads1, 2, and 3 should have one half the resistance to those leads to which they have continuity as the other two have to each other Arbitrarily name 1, 2, & 3.
Changing the voltage to a motor with unmarked leads now wired;Dual voltage Wye connected
Example motor is wired 440 volt connected.
1-Arbitrarily mark line, (to power), leads 1,2, and 3. And disconnect lines. Mark each individual wire of the three pairs of wires connected A, B, & C
2-Separate A&A and check each for continuity with 1, 2, & 3. 4 will have continuity with 1, 5 with 2, and 3 with 6. The one originally paired with 4 (A, B OR C), will be 7, originally paired with 5 (A. B. or C), will be 8 and originally paired with 6 (A, B or C), will be 9
Dual voltage Delta connected
Example motor is wired 440 volt connected.
1-Arbitrarily mark line, (to power), leads 1,2, and 3. And disconnect lines. Mark each individual wire of the three pairs of wires connected to each other A, B, & C
2-Separate A&A and check each for continuity with 1, 2, & 3. 1 will have continuity with 9 and 4, 2 will have continuity with 7&5, 3 will have continuity with 6 & 8.Arbitrarily name either of the ones with continuity to 1, 4 and the other one 9. The one originally paired (from pairs AA, BB, or CC), with 4 is 7. Name one that has continuity with 7 & 3, 8. Name the remaining one with continuity with 2, 5 and the last unmarked lead should be 6, which has continuity with 3 & 8.
Question: I have lost track of the leads of a nine lead three phase motor. How can I re-identify these leads?
Answer: For the purpose of this test, a lantern battery of six or nine volts works best. Use a DC volt-ohm meter with a 20K ohms per volt DC scale. Battery and voltmeter leads should be properly identified. Alligator clips should be used on both. The motor must be completely assembled. Test the nine leads for continuity with the ohmmeter to determine whether the motor is star (wye) or delta connected. The delta connected motor will possess three sets of three leads with continuity between them. On the other hand, the star connected motor will have only one set of three leads with continuity between them, and three sets of two leads with continuity. Following are specific steps to take when identifying leads of both a star connected and a delta connected motor. Refer to the diagrams on the following page for further details.
Delta Connected Motor:
Using an ohmmeter, identify the three groups of three leads. Separate these groups by tying them with tape. Attach leads to a pair of wires in a group, and observe the voltage drop from each pair of energized leads to the third lead in that group. Continue until a combination is found that gives a voltage drop from each of the energized leads to the third lead equal to one half of the battery voltage. The lead located halfway between the other two will thus be the corner lead of the delta. Repeat this for each group of leads, marking the corner leads #1, #2, and #3.
Next, use the inductive kick test method to identify the proper markings for the other two leads of each group. The two coils #3 & #6 and #3 & #8, acting in parallel, will produce the effect of a coil positioned halfway between the actual position of the two coils. The flux produced by #3 & #6 and #3 & #8 combined, will be perpendicular to the axis of #1 & #4 and #2 & #7. Opening and closing a switch in this circuit will produce a kick in coils #1 & #9 and #2 & #5, but no kick in #1 & #4 and #2 & #7.
Therefore, if the battery is connected from #3 & #6 and #3 & #8 as shown, opening and closing the battery circuit, the voltmeter will identify leads #1, #4, and #9 and can be distinguished by noting the magnitude rather than the polarity. The voltmeter can then be connected to terminal #2 for determination of the leads #5 & #7. Leads #2 to #7 will give little or no deflection, and leads #2 to #5 will give a substantial deflection.
In succession, the battery is then transferred to the corner of #1. Tie the battery between leads #1 & #4 & #9. Making and breaking the circuit will be perpendicular to #3 & #8 and #2 & #5, resulting in no deflection. However, there will be a deflection from leads #2 & #7 and #3 & #6. Placing the battery next on the #2 & #5 and #2 & #7 leads will be perpendicular to #1 & #9 and #3 & #6 leads, therefore creating no deflection. Leads #1 & #4 and #3 & #8 would then have a deflection, thus concluding the lead testing of the nine lead delta connected motor.

Star Connected Motor:

11. Junior Member
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Jul 2007
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Thank You!!! This is the answer that I have been looking for! It looks like a Delta Wound Motor by the tag. I will try to do this this weekend. I appreciate everyone's help on this, You guys are great!!!

12. Titanium
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nowhereville
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Here, this might help. I simply searched google and was one of the first as anyone could do.

http://www.lewellyn.com/pdf/os_pdf/Unmarked_Delta.pdf

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