SPEED TORQUE CHARACTERSTICS OF 3 PHASE INDUCTION MOTOR BY GYAN VARDHAN TYAGI DHEERAJ SHARMA

The per phase equivalent circuit of an induction motor is shown below:

IM -Induction Motor Rs -Stator Resistance Rr -Rotor Resistance Rr’ -Rotor Resistance Referred to Stator side Xs -Stator Reactance Xr -Rotor Reactance Xr’ -Rotor Reactance Referred to Stator side Xm -Leakage Inductance I1 -Stator Current I2 -Rotor Current I2’ -Rotor Current Referred to Stator side Im -Magnetizing Current V0 -Stator Voltage s -Slip ωs- Synchronous Speed ωm- Rotor Speed (Machine Speed) Ωs -Average Synchronous Speed (in RPM) f -Supply Frequency p -No. of Poles Pg- Air-gap Power Pcu- Copper loss in the machine Pm -Mechanical Power output of the machine T -Torque Developed by the motor sm- Slip at maximum torque

Tmax- Maximum Torque ωsl- Slip Speed ωf -Rotor Speed at Frequency f

CALCULATION OF TORQUE s = (ω s – ωm)/ ω s ω s = 120f/p rpm

Power transferred to rotor (or air-gap power) Pg=3I2R/s Rotor current I2=V0/{(Rs+Rr/s)+j(Xs+Xr)} Power transferred to rotor (or air-gap power) Pg=3I2R/s Rotor copper loss is Pcu=3I2Rr

Electrical power converted into mechanical power Pm=Pg-Pcu=3I22Rr{(1-s)/s} Torque developed by motor T=Pm/ ωm Thus, T= 3I22Rr/s ω s

SIMULATION MODEL

RESULTS