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How to determine polarity on three phase motor? 7
- Thread starter cccelcj
- Start date
Maybe this is the answer you're looking for (maybe this is too trivial?):
Usually, identifying which lead is which is not important. Usually, all that matters is phase rotation -- that is, A-B-C or B-C-A or C-A-B are usually all acceptable -- they all lead to rotation in the same direction.
There's only two choices for rotation, clockwise or counterclockwise. Reverse phase rotation will make your motor spin the wrong way. You've got a 50-50 chance of getting it right the first time.
So then, the usual procedure, so far as I know, is to take a guess at wiring the motor, see if it spins the right way by "bumping" it (momentary energization -- don't continuously energize it or some motor designs might be damaged), and if it turned out it was wired the wrong way, you switch two of the leads.
Hope that helps. Others might have additional insights.
Usually, identifying which lead is which is not important. Usually, all that matters is phase rotation -- that is, A-B-C or B-C-A or C-A-B are usually all acceptable -- they all lead to rotation in the same direction.
There's only two choices for rotation, clockwise or counterclockwise. Reverse phase rotation will make your motor spin the wrong way. You've got a 50-50 chance of getting it right the first time.
So then, the usual procedure, so far as I know, is to take a guess at wiring the motor, see if it spins the right way by "bumping" it (momentary energization -- don't continuously energize it or some motor designs might be damaged), and if it turned out it was wired the wrong way, you switch two of the leads.
Hope that helps. Others might have additional insights.
Some systems, most notably vertical shaft pumps, can be totally destroyed by spinning backwards just a few revolutions so do make sure your load would allow it.
Keith Cress
Flamin Systems, Inc.-
Keith Cress
Flamin Systems, Inc.-
Hello cccelcj
It reads like you need to identify 6 leads, Are you asking for connection of 6 wires externally or just three? If just three the previous post got it covered, if not does it need to be connected Wye or delta?
The more info you can supply will help get you a better answer. I like to bump or jog the motor w/no load.
Chuck
It reads like you need to identify 6 leads, Are you asking for connection of 6 wires externally or just three? If just three the previous post got it covered, if not does it need to be connected Wye or delta?
The more info you can supply will help get you a better answer. I like to bump or jog the motor w/no load.
Chuck
-
2
- Moderator
- #5
1> Identify each winding.
EG A1, A2; B1, B2; C1, C2.
Spin the motor up to speed with another motor.
Energise A1, A2. For use 480 volts and fuse for about 75% of nameplate current. If the fuse blows repeatedly the motor is probably intended for wye operation. Ruduce the voltage to 240 volts and continue. The motor is now running as an induction generator and we can use the voltages output on the windings to easily determine the connections.
Connect B1 to A2. Read the voltage from A1 to B2. If it is equal to the applied voltage it is connected correctly.
If the A1 to B2 voltage is approximately 1.73 times the applied voltage one of the windings is reversed. Reverse B1 and B2.
Now connect C2 to A1. Check the voltage from C1 to B2. If it is zero or close to it the connections are correct. If the voltage is approximately twice applied voltage reverse the "C" winding connections. When the voltage between the free ends of the "C" wionding and the "B" winding are zero or close to it, you can connect them and the motor is now wired in delta.
Now if any of the windings have been reversed, make sure the labels have also been reversed. Your connections should be A2 with B1, B2 with C1, C2 with A1.
To change to a wye connection, connect power to A1, B1, C1, and connect A2, B2, and C2 together.
Nema motors are often star-delta start and use the delta connection for the high voltage or rated voltage connection.
IEC motors are often dual voltage and use the wye or star connection for the higher voltage.
yours
EG A1, A2; B1, B2; C1, C2.
Spin the motor up to speed with another motor.
Energise A1, A2. For use 480 volts and fuse for about 75% of nameplate current. If the fuse blows repeatedly the motor is probably intended for wye operation. Ruduce the voltage to 240 volts and continue. The motor is now running as an induction generator and we can use the voltages output on the windings to easily determine the connections.
Connect B1 to A2. Read the voltage from A1 to B2. If it is equal to the applied voltage it is connected correctly.
If the A1 to B2 voltage is approximately 1.73 times the applied voltage one of the windings is reversed. Reverse B1 and B2.
Now connect C2 to A1. Check the voltage from C1 to B2. If it is zero or close to it the connections are correct. If the voltage is approximately twice applied voltage reverse the "C" winding connections. When the voltage between the free ends of the "C" wionding and the "B" winding are zero or close to it, you can connect them and the motor is now wired in delta.
Now if any of the windings have been reversed, make sure the labels have also been reversed. Your connections should be A2 with B1, B2 with C1, C2 with A1.
To change to a wye connection, connect power to A1, B1, C1, and connect A2, B2, and C2 together.
Nema motors are often star-delta start and use the delta connection for the high voltage or rated voltage connection.
IEC motors are often dual voltage and use the wye or star connection for the higher voltage.
yours
cccelcj.
To have a better idea of your problem and a possible solution check and report the following:
1- Asign arbitrary numbers from 1 to 6
2- Check for continuity bettween the six cables you have.
3- Measure resistance in Ohms between the terminals that showed continuity.
To have a better idea of your problem and a possible solution check and report the following:
1- Asign arbitrary numbers from 1 to 6
2- Check for continuity bettween the six cables you have.
3- Measure resistance in Ohms between the terminals that showed continuity.
coconutalley
Electrical
How about contacting the manufacturer? They should have their name or logo on the nameplate.
Hello CCCELCJ,
The Waross method sound good but the matter is how you coupled the prime mover to the motor?? what happened with large and high voltage motors??
Adding to the aolalde comments I will suggest:
1. Random to three wires Asign arbitrary numbers from 1 to 3
2. Check the continuity between the no marked and marked wires: Continuity with 1 is marked like 4, continuity with 2 is marked like 5 and continuity with 3 is marked with 6.
3. You could use the surge tester, and find the lead combination that gives the correct pattern (1-6, 2-4, 3-5).
4. Check the right name plate connection (wye or Delta)
5. Check Insulation and start the motor.
The Waross method sound good but the matter is how you coupled the prime mover to the motor?? what happened with large and high voltage motors??
Adding to the aolalde comments I will suggest:
1. Random to three wires Asign arbitrary numbers from 1 to 3
2. Check the continuity between the no marked and marked wires: Continuity with 1 is marked like 4, continuity with 2 is marked like 5 and continuity with 3 is marked with 6.
3. You could use the surge tester, and find the lead combination that gives the correct pattern (1-6, 2-4, 3-5).
4. Check the right name plate connection (wye or Delta)
5. Check Insulation and start the motor.
- Moderator
- #9
Don't forget that the relative polarity of the individual windings is important. If one winding is reverse connected, you may have a displacement between windings of 60 Deg. 60 Deg and 240 deg., instead of the correct 120 deg., 120 deg., 120 deg. A motor acts as an induction generator and will be trying to generate back emfs at 120 deg. displacement. The motor will be unhappy.
If the motor can not be turned with another motor, try single phasing it. Connect some capacitors in series with one winding and connect the second winding in parallel with the first winding. Use a switch so that when the motor starts you can disconnect the connection to the capacitors and leave the motor running single phase on one winding, with another winding connected on one end and free on the other end. Apply voltage and try to start the motor with single phase. You may have to reverse the leads of one of the windings to get the motor to start. When you get it running on one phase, open the switch and follow the procedure for checking the voltage at the open end of the winding.
respectfully
If the motor can not be turned with another motor, try single phasing it. Connect some capacitors in series with one winding and connect the second winding in parallel with the first winding. Use a switch so that when the motor starts you can disconnect the connection to the capacitors and leave the motor running single phase on one winding, with another winding connected on one end and free on the other end. Apply voltage and try to start the motor with single phase. You may have to reverse the leads of one of the windings to get the motor to start. When you get it running on one phase, open the switch and follow the procedure for checking the voltage at the open end of the winding.
respectfully
- Thread starter
- #10
So, from what I am reading from the replies, it does not matter which number are assigned to a particular coil? Could phasing or direction of coil winding be a consideration. I am not certain if it is a delta or a star. How would I determine if it is a delta or a star. I recently got into motor field service and am sure to run across these situations in the future. This site seems to be full of experienced individuals. I have experience in drives and controls, but have never really gone as far as I feel I am headed. Hope you guys don't mind if I pick your brains from time to time.
- Thread starter
- #11
- Moderator
- #12
This is not 100%
A NEMA motor is probably delta for star delta starting.
An IEC motor is probably Star for dual voltage use.
A delta motor connected star will be underpowered and slow starting. The slip will be excessive.
A Star motor connected delta will probably blow the fuses because of overvoltage saturation. I would be aware of this and use appropriate fuses and monitor the current the first time starting an unknown motor in delta.
Respectfully
A NEMA motor is probably delta for star delta starting.
An IEC motor is probably Star for dual voltage use.
A delta motor connected star will be underpowered and slow starting. The slip will be excessive.
A Star motor connected delta will probably blow the fuses because of overvoltage saturation. I would be aware of this and use appropriate fuses and monitor the current the first time starting an unknown motor in delta.
Respectfully
Once you find the correct wire marks: Start the motor in wye at rating voltage and with no load and read the Current , if you have a value from 20 to 30% of Rated current this is the right connection if you read a very low current the right connection will Delta.
For Wye: L1--- 1 L2--- 2 L3--- 3 and 4-5& 6 Together
Delta: L1-- 1&6 L2-- 2 & 4 L3-- 3 & 5
Regards
Petronila
For Wye: L1--- 1 L2--- 2 L3--- 3 and 4-5& 6 Together
Delta: L1-- 1&6 L2-- 2 & 4 L3-- 3 & 5
Regards
Petronila
bigbillnky
Electrical
cccelcj
Are you sure that this motor is not a part-winding start?
Bigbillnky,C.E.F.....(Chief Electrical Flunky)
Are you sure that this motor is not a part-winding start?
Bigbillnky,C.E.F.....(Chief Electrical Flunky)
- Thread starter
- #15
- Moderator
- #16
- Thread starter
- #17
So,since I do have three groups of three, I might have a wye-delta. Part of the problem I am having is that when the motor was energized it drew extremely high amps trippping the circuit breaker. The nameplate shows no data other than the power connections which list L1 to 1, L2 to 2 and L3 to 3. Would there be any problem with starting this motor right across the line? It is a new installation on a pumping application.
- Moderator
- #18
cccelcj
Looks like a typo? Three groups of three would be 9 wires. I understood you had 6 wires. I understood that there were three groups of two leads but I am not sure.
High current may indicate:
1> One winding is reversed. (Either star or delta)
2> Voltage is not right for the connection.
The load is stalling the motor.
Can you run the motor free or is it coupled up to a machine?
Can you describe your breaker?
Have you been able to measure the motor amps?
Can you give us a make and model of the motor?
respectfully
Looks like a typo? Three groups of three would be 9 wires. I understood you had 6 wires. I understood that there were three groups of two leads but I am not sure.
High current may indicate:
1> One winding is reversed. (Either star or delta)
2> Voltage is not right for the connection.
The load is stalling the motor.
Can you run the motor free or is it coupled up to a machine?
Can you describe your breaker?
Have you been able to measure the motor amps?
Can you give us a make and model of the motor?
respectfully
- Thread starter
- #19
- Moderator
- #20
Hello cccelcj
I checked the siemens web site and it appears that your motor is a wye-delta start motor.
It appears that you have one winding reversed.
There are two ways to go;
One way is to spin the motor up.
The other way is to trip the breaker a few more times.
Start on the wye connection. This is the normal starting connection and the current and the stresses on the motor will be less with this connection.
1> Identify the leads from each winding.
2> Connect one lead from each winding together and insulate or make safe.
3> apply three phase 480 volts to the remaining thre leads.
4> if the motor starts go to part two.
5> If the current is excessive, reverse the connections of one winding.
6> If the motor starts go to part two.
7> If the current is excessive, return the connections that you reversed to the original connection and reverse another set.
8> If the motor starts go to part two.
9> If the current is excessive, return the connections that you reversed to the original connection and reverse another set.
If you are not able to start the motor by now, inspect the motor for damage and check that the load is not stalling the motor.
You should have the motor running on the star connection.
Part Two
Delta connection.
1> Mark the three line leads 1, 2, and 3.
2> Mark the other end of "1" as "4".
3> Mark the other end of "2" as "5".
3> Mark the other end of "3" as "6".
Your connections for 480 volt delta are:
Line 1, 1 and 6
Line 2, 2 and 4
Line 3, 3 and 5
respectfully
I checked the siemens web site and it appears that your motor is a wye-delta start motor.
It appears that you have one winding reversed.
There are two ways to go;
One way is to spin the motor up.
The other way is to trip the breaker a few more times.
Start on the wye connection. This is the normal starting connection and the current and the stresses on the motor will be less with this connection.
1> Identify the leads from each winding.
2> Connect one lead from each winding together and insulate or make safe.
3> apply three phase 480 volts to the remaining thre leads.
4> if the motor starts go to part two.
5> If the current is excessive, reverse the connections of one winding.
6> If the motor starts go to part two.
7> If the current is excessive, return the connections that you reversed to the original connection and reverse another set.
8> If the motor starts go to part two.
9> If the current is excessive, return the connections that you reversed to the original connection and reverse another set.
If you are not able to start the motor by now, inspect the motor for damage and check that the load is not stalling the motor.
You should have the motor running on the star connection.
Part Two
Delta connection.
1> Mark the three line leads 1, 2, and 3.
2> Mark the other end of "1" as "4".
3> Mark the other end of "2" as "5".
3> Mark the other end of "3" as "6".
Your connections for 480 volt delta are:
Line 1, 1 and 6
Line 2, 2 and 4
Line 3, 3 and 5
respectfully
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