1. PowerPoint Presentation for ER 2030
Three-Phase Motors
PowerPoint Presentation for ER 2030

2. Rotating Magnetic Field
Three-Phase Motors
Rotating Magnetic Field
The principle of operation for all three-phase motors is the rotating magnetic field.
The magnetic field rotation is caused by:
– voltages are 120° out of phase.
– voltages periodically change polarity.
– the arrangement of the stator windings.

3. Three-phase stator and three voltage sine waves.
Three-Phase Motors
Three-phase stator and three voltage sine waves.

4. The magnetic field is concentrated between poles 1A and 1B.
Three-Phase Motors
The magnetic field is concentrated between poles 1A and 1B.

5. The magnetic field is concentrated between poles of phases 1 and 2.
Three-Phase Motors
The magnetic field is concentrated between poles of phases 1 and 2.

6. The magnetic field is concentrated between poles 2A and 2B.
Three-Phase Motors
The magnetic field is concentrated between poles 2A and 2B.

7. The magnetic field is concentrated between phases 2 and 3.
Three-Phase Motors
The magnetic field is concentrated between phases 2 and 3.

8. The magnetic field is concentrated between poles 3A and 3B.
Three-Phase Motors
The magnetic field is concentrated between poles 3A and 3B.

9. The magnetic field is concentrated between phases 1 and 3.
Three-Phase Motors
The magnetic field is concentrated between phases 1 and 3.

10. AC Motors Animation

11. Three-Phase Motors Synchronous Speed
Synchronous speed is the rotational speed of the magnetic field.
Synchronous speed is determined by:
– the number of stator poles per phase.
– the frequency of the applied voltage.

12. Three-Phase Motors
RPM
STATOR POLES
3600 2
1800 4
1200 6
900 8

13. Three-Phase Motors Synchronous Speed S = (120 x F) / P
S = synchronous speed in RPM
F = frequency in Hz
P = number of stator poles

14. Three Phase Motors Torque
Three factors determine the amount of motor torque:
– the strength of the stator magnetic fields.
– the strength of the rotor magnetic fields.
– the phase angle difference between the rotor and stator fields.

15. Three-Phase Motors Phase Rotation
The direction of rotation is either clockwise or counterclockwise.
Reversing any two of the stator leads will reverse the direction of rotation.
A phase rotation meter can determine the direction of rotation.
Motor stator leads are often called T leads.

16. Three Phase motors An induction motor never reaches synchronous speed.
Slip
An induction motor never reaches synchronous speed.
Slip is the difference between synchronous speed and rotor speed.
Percent slip is the ratio of slip to synchronous speed times 100.

17. Connecting the phase rotation meter to the motor.
Three-Phase Motors
Connecting the phase rotation meter to the motor.

18. Connecting the phase rotation meter to the line.
Three-Phase Motors
Connecting the phase rotation meter to the line.

19. Standard numbering for three-phase motors.

20. Three-Phase Motors
For more information on stator windings, watch these videos:
Three Phase Motors Video 01
Three Phase Motors Video 02

21. Standard high-voltage wye connections.
Three-Phase Motors
Standard high-voltage wye connections.

22. Standard high-voltage delta connections.
Three-Phase Motors
Standard high-voltage delta connections.

23. Standard low-voltage wye schematic.
Three-Phase Motors
Standard low-voltage wye schematic.

24. Standard low-voltage wye chart and diagram.
Three-Phase Motors
Standard low-voltage wye chart and diagram.

25. Standard low-voltage delta schematic.
Three-Phase Motors
Standard low-voltage delta schematic.

26. Standard low-voltage delta chart and diagram.
Three-Phase Motors
Standard low-voltage delta chart and diagram.

27. 12-Lead Dual-Voltage Motors
Three-Phase Motors
12-Lead Dual-Voltage Motors
Some motors will have 12 T leads brought to the terminal box instead of the usual 9 leads.
These motors are intended for wye-delta starting.
Wye-delta starting helps limit inrush starting current.

28. Standard 12-lead motor schematic.
Three-Phase Motors
Standard 12-lead motor schematic.