Three Phase Dual Voltage Motor Information

Warning

Only qualified individuals should work on electrical equipment. Always turn power off to the device you are working on and LOCK IT OUT. Then, before working on the equipment check the power leads with a known working multimeter to verify that the correct circuit was locked out. It's much better to be doubly safe than DEAD.

Table of Contents

• "Y" Connected, 9 lead
• "Delta" Connected, 9 lead
• "Y" Connected, 12 lead
• How to Use this Information
• Electrical Formulas

Single Speed Three Phase Motors, 9 leads, "Y" connection

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Single speed three phase motor, 9 leads, "Delta" connection

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Single speed Three Phase motor, 12 leads, External "Y" connection

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How to Use this Information

Note: Disconnect all wiring to the motor and the motor leads before taking any measurements, otherwise your readings may back feed through the rest of the machine wiring and give inaccurate results.

Identify an unknown motor

For example, You have a Three Phase Dual Voltage (240/480 vac) motor and there is not a wiring diagram attached. Disconnect all leads and measure continuity through the windings. Compare your findings with the "Y" connection diagram and the "Delta" connection diagram to determine winding style. A "Y" connected motor will have continuity through wires 7-8-9, a "Delta" motor will have continuity through wires 7-5-2. Look at the pictures and you'll see the difference.

Verify a motor is damaged or not

If you know the motor is "Y" or "Delta" connected use a multi-meter to measure continuity through the windings. A "Y" motor should have continuity through wires 1 and 4, 2 and 5, 3 and 6, and through 7 to 8 to 9. If there is not continuity through any of the wiring sets then you have an open winding, and the motor is bad. Use the "Delta" drawing for motors wired with a "Delta" connection, following the example of "Y" for lead continuity. Also verify each winding set has NO continuity to ground, if any winding has continuity to ground then the winding is shorted to ground, and the motor is bad.

Switch voltages from high to low or back

If a High/Low voltage wiring connection plate is not attached to the motor you can use the tables above to switch voltages. Make sure you know if the motor is "Y" or "Delta" connected or motor damage will result.

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Some Basic Electrical Formulas

If you use formulas occasionally a handy trick is to set up a spreadsheet that has the formulas built in, then all you need to do is enter the numbers to determine the values.

Ohms Law

Ohms = Volts / Amperes (R = E/I)

Amperes = Volts / Ohms (I = E/R)

Volts = Amperes * Ohms (E = IR)

Power, AC Circuits

Efficiency

             746 * Output Horsepower
Efficiency = _______________________
                  Input Watts

Three Phase Kilowatts

                        Volts * Amperes * Power Factor * 1.732

Three Phase Kilowatts = ______________________________________
                                          1000

Three Phase Volt Amperes

Three Phase Volt Amperes = Volts * Amperes * 1.732

Three Phase Amperes

                                   746 * Horsepower  
Three Phase Amperes = _________________________________________
                      Volts * Efficiency * Power Factor * 1.732 

Disclaimer

The information presented in this tutorial has been learned from experience and obtained from a number of sources. Efforts had been made to assure the accuracy of the information, however no warranty is expressed or implied, and no liability or responsibility can be accepted for incorrect information. All calculations or information should be independently verified.