Group Members:

• Asad Tanvir (12EL13)

• Uzair Nazir (12EL35 )

• Wasif Hussain (12EL36)

• Azfar Rasool (12EL04)

• Mosa Ali (12EL37)

Introduction of Topics:

•Power Equations

• Effect of changes in shaft load

• Effect of changes in field excitations

Power Equation

• What is Power Equations

Simply!

Prepare for complex thing..

Power Equations in Induction Motor

• Electric Circuit of Induction Motor

Power Equations in Induction MotorDerivations

Power Flow Diagram

Easy or Tough Numerical Problem

A 460-V, 25-hp, 60 Hz, 4 pole, Y-connected motor with the power factor of 33.6 lagging has the stator copper losses of 685W. It has following impedances:

R1=0.641 R2=0.322

X1=1.106 X2=0.464

Xm=26.3

The slip of the induction motor is 0.2% and it drives the load current of 18.88A. Assuming core and frictional losses are negligible. Find the power converted or electromechanical power generated?

Effect of load changes of

synchronous motor

If load is attached to the shaft of synchronous motor the will develop enough torque to keep the motor and its load turning at synchronous speed

What happens when load is changed on synchronous motor

If load on the shaft on the motor is increased

• The rotor will initially slow down

• As it does ,the torque angle alpha becomes larger and induced torque increased

• The increase in induced torque eventually speed up , and the motor gain turns at synchronous speed

(b) Assume that the shaft load is now increased to 30 hp. Sketch the behavior of thephasor diagram in response to this change

(b) As the power on the shaft is increased to 30 hp, the shaft slows momentarily, andthe internal generated voltage EA swings out to a larger angle /j while maintaininga constant magnitude. The resulting phasor diagram is shown in Figure 6-7b.

Following phenomenon will occurs

Rotor speed decrease

Slip increase

Smaller amount of induced voltage is developed

Power factor will improve

Torque will increase

Variable Load Change :

•Under extreme load changes, e.g. frequent starts / stops, or high inertial loads, this method of calculating

the motor rating is unsuitable since it would underestimate the heating that would occur.

Effect of changes field excitation

•Increases excitation •Decreases excitation

•Power factor will improve and adjusted

•Pull out torque will increase

•No slipping of poles

• Leading power factor will occur

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Any Questions?