FINDING THE TORQUE–SPEED CHARACTERISTIC OF AN INDUCTION MOTOR FOR VARYING ROTOR RESISTANCE

Repeat Example 14.3 for rotor resistance $R_{r}$ = 0.1 Ω, 0.2 Ω, 0.3 Ω, and 0.42 Ω. The slip is kept fixed at s = 0.1.

Question

FINDING THE TORQUE–SPEED CHARACTERISTIC OF AN INDUCTION MOTOR FOR VARYING ROTOR RESISTANCE

Repeat Example 14.3 for rotor resistance [latex]R_{r}[/latex] = 0.1 Ω, 0.2 Ω, 0.3 Ω, and 0.42 Ω. The slip is kept fixed at s = 0.1.

Accepted Answer

The PSpice schematic is similar to that as shown in Figure 14.9. The rotor resistance is varied by using the PSpice parametric command .PARAM.

The listing of the circuit file is as follows:

Example 14.4 Torque–speed characteristic with variable rotor resistance

SOURCE VS 1 0 AC 170V ; Input voltage of 170V
CIRCUIT .PARAM SLIP = 0.1 ; Slip

.PARAM RRES = 0.42 ; Rotor resistance
.PARAM RSLIP = {RRES* (1-slip)/slip}
.STEP PARAM RRES LIST 0.1 0.2 0.3 0.42 ; List values
VX 1 2 DC 0V ; Senses the stator current
RS 2 3 {RRES}
LS 3 4 2.18MH

LM 4 0 58.36MH
LR 4 5 2.18MH
RR 5 6 {RRES}
RX 6 7 {RSLIP}
VY 7 0 DC 0V ; Senses the rotor current

ANALYSIS .AC DEC 100 0.1HZ 100HZ ; AC analysis

.OPTIONS ABSTOL = 1.00N RELTOL = 0.01 VNTOL = 0.1
ITL5 = 0
.PROBE ; Graphics post-processor

.END

The plots of the torque developed [latex]T_{d}[/latex]= V(5) × I(Vy)/2/(2 × 3.14 × Frequency) vs. frequency for various slips are shown in Figure 14.11. The torque increases as the rotor resistance is reduced.

Question 14.4: FINDING THE TORQUE–SPEED CHARACTERISTIC OF AN INDUCTION MOTO...

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