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

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

Three-phase stator and three voltage sine waves. Three-Phase Motors The magnetic field is concentrated between poles 1A and 1B.

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

The magnetic field is concentrated between poles 2A and 2B. Three-Phase Motors The magnetic field is concentrated between phases 2 and 3.

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

phases 1 and 3. AC Motors Animation http:// www.physclips.unsw.edu.au/jw/ele ctricmotors.html#DCmotors

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. Three-Phase Motors RPM STATOR POLES

3600 2 1800 4

1200 6 900 8

Three-Phase Motors Synchronous Speed

S = (120 x F) / P S = synchronous speed in RPM F = frequency in Hz P = number of stator poles 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.

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. Three Phase motors 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. Three-Phase Motors

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

Three-Phase Motors Standard numbering for three-phase motors. Three-Phase Motors For more information on stator windings,

watch these videos: Three Phase Motors Video 01 Three Phase Motors Video 02 Three-Phase Motors Standard high-voltage wye connections.

Three-Phase Motors Standard high-voltage delta connections. Three-Phase Motors Standard low-voltage wye schematic.

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

Three-Phase Motors Standard low-voltage delta chart and diagram. 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 wyedelta starting. Wye-delta starting helps limit inrush starting current. Three-Phase Motors

Standard 12-lead motor schematic.