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## Motor Tutor

### 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.

• How to Use this Information
• Electrical Formulas

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

#### Dual Voltage, Three Phase, "Y" Connected, 9 wire

Voltage L1 L2 L3 Join
Low 1, 7 2, 8 3, 9 4&5&6
High 1 2 3 4&7, 5&8, 6&9

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

#### Dual Voltage, Three Phase, "Delta" Connected, 9 wire

Voltage L1 L2 L3 Join
Low 1, 6, 7 2, 4, 8 3, 5, 9 ---
High 1 2 3 4&7, 5&8, 6&9

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

#### Dual Voltage, Three Phase, External "Y" Connected, 12 wire

Voltage L1 L2 L3 Join
Low 1, 7 2, 8 3, 9 4&5&6, 10&11&12
High 1 2 3 4&7, 5&8, 6&9, 10&11&12

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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 HorsepowerEfficiency = _______________________                  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.