Operating principle

• Rotating magnetic field created by stator induces e.m.f in rotor
• Current flows through short circuited winding of the rotor
• The current interacts with the rotating flux to produce a torque that causes the motor to rotate in the direction of the rotating magnetic field
• The speed of the rotor is nearly equal to the synchronous speed at no load
• As the load increases, this induction speed drops slightly

• The total input power measured by two wattmeters (110V, 0 - 15/0-30 HW)
• The stator current and voltage with an A.C. ammeter (0-20A) and an A.C. voltmeter(0-150V)
• The speed is measured by a tachometer (0 - 9999 r.p.m.), and the supply frequency by a frequency meter(45-55Hz)
• 3 phase variac used for starting of the motor
• Separately Excited DC Generator for loading the induction motor
• Two d.c. ammeters (0-5A for measuring the field current and 0-20A for measuring armature current), and one d.c voltmeter (0-150V) to measure the voltage in the load
• 20A , 110V Loadbox for loading the d.c. generator

Calculation of Performance Parameters

• Power factor of induction machine (cos θ) = (W1 + W2) / (v3xVxI )
  where, V and I are induction motor input voltage and current,
  and W1 + W2 is the Total power input to the induction motor
• Output of motor (Pout) = Input of the D.C generator = Vd.c x Id.c / ηd.c.
  where ηd.c. = efficiency of the D.C. generator,
  and Vd.c & Id.c are d.c. generator armature voltage and current
• Efficiency of the induction motor (?a.c )= Output / input = (Vd.c x Id.c / ηd.c.) / (W1 + W2)
• Torque of induction motor( T )= Pout / (2 x p x nr) where nr is the speed of induction motor in r.p.m.