08-05-2012, 04:50 PM
TRANSFER FUNCTION OF SEPARATELY EXCITED DC SHUNT GENERATOR
51355420-LAB-MANUAL-FOR-E-E-CS.pdf (Size: 523.09 KB / Downloads: 78)
FORMULAE
1.Generated EMF Constant (Kg) = Eg / If in Volts / Amps (From the Graphs)
2. Field Resistance (Rf) = Vf / If
3. Effective Resistance (Reff) = VL/ IL in Volts / Amps (From the Graphs)
Where, VL = Change in load voltage in volts
IL = Change in load current in amps
4. Load Resistance (RL) = PL / IL
2
Where, RL = Load Resistance in Ohms
PL = Power of Load in Watts
IL = Total Load current in Amps
5. Field Inductance Lf
Where, Xf= (Zf
Xf= 2f Lf
Lf= Xf / 2f
f = frequency of applied source in hertz
6.Transfer function
Eg(s) Ef(s) = (No Load)
Vt (s) / Ef(s) = (Load)
PRECAUTION
1. The motor field rheostat should be kept at minimum resistance position.
2. The motor armature rheostat should be kept at maximum resistance position.
3. At the time of starting, the motor should be in no load condition.
(Kg / Rf )
(1+ (Lf / Rf) S) (1+ (Reff / RL))
(Kg / Rf )
(1+ (Lf/Rf) S)
EC2259 Electrical Engineering And Control System Lab Manual
Prepared by G.Panneerselvam, Vel Tech Multi Tech
PROCEDURE
To find out Generated EMF Constant (Kg)
1. Connections are given as per the circuit diagram.
2. The motor is made to run at the rated speed.
3. The generated emf is noted for various values of field current.
4. The voltage across the field winding is also measured
5. From the OCC curve Back Emf constant is calculated.
To find out Field Impedance (Zf)
1. Connections are given as per the circuit diagram.
2. Using single phase variac the supply voltage is varied.
3. The corresponding reading of field current is noted for different values of applied voltage.
4. From the noted readings the field Impedance is calculated.