blob: 8aafafe27243ae25dc87a0d336bb5bb1577b8642 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
//Chapter 6:Induction Motor Drives
//Example 17
clc;
//Variable Initialization
//Ratings of the star connected Induction motor
f=50 // frequency in HZ
Vl=440 //line voltage in V
P=6 // number of poles
Ns=120*f/P //synchronous speed
//Parameters referred to the stator
Xr_=1.2 // rotor winding reactance in ohm
Xs=Xr_ // stator winding reactance in ohm
Rr_=0.4 // resistance of the rotor windings in ohm
Rs=0.5 // resistance of the stator windings in ohm
Xm=50 // magnetizing reatance
a=3.5 // stator to rotor turns ratio
delta=0 // duty ratio at the given breakdown torque
Sm=1 // slip at standstill
//Solution
//Slip at maximum torque without an external resistance is Sm=Rr_/sqrt(Rs**2+(Xs+Xr_)**2)
//When an external resistanc Re referred to the stator is connected
x=Sm*sqrt(Rs**2+(Xs+Xr_)**2) //x=Re+Rr_
Re=x-Rr_
y=0.5*a**2*(1-delta) // y=0.5*a**2*R*(1-delta) //y=Re
R=Re/y
//(Ns-N)/Ns
//(Ns/Ns)-(N/Ns)
Sm=(Ns/Ns)-(1/Ns)
c=(x*Sm-Rr_)/(0.5*a**2*R) //c=(1-delta)
delta=1-c //given duty ratio
//Results
mprintf("Variation of the duty ratio is:%.3f*N*10**(-3)",delta*1000)
mprintf("\nHence the duty ratio must change linearly with speed N")
|
