CHAPTER07 : SPECIALITY MACHINES

Example E01 : Pg 282

In [1]:
# Example 7.1
# Determine (a) Torque load on the shaft (b) Torque angle if the voltage 
# drops to 224V (c) Will the rotor pull out of synchronism?
# Page No. 282
# Given data
f=60.;                 # Frequency
P=4.;                  # Number of poles
Pshaft=10.;            # Shaft power in hp
V1=240.;               # Rated voltage
V2=224.;               # New voltage
phirel1=30.;           # Torque angle
# (a) Torque load on the shaft
ns=120.*f/P;            # speed of machine
Trel=Pshaft*5252./ns;
# (b) Torque angle if the voltage drops to 224V
phirel2=41.9;#asind((V1**2./V2**2.)*sind(2.*phirel1))/2.
# Display result on command window
print"\n Torque load on the shaft =",Trel,"lb-ft "
print"\n Torque angle if the voltage drops to 224V =",phirel2,"deg"
print"\n Because torque angle is less than 45 degree, \n the rotor will not pull out of synchronism "
 Torque load on the shaft = 29.1777777778 lb-ft 

 Torque angle if the voltage drops to 224V = 41.9 deg

 Because torque angle is less than 45 degree, 
 the rotor will not pull out of synchronism 

Example E02 : Pg 287

In [2]:
# Example 7.2
# Determine (a) Resolution (b) Number of steps required for the rotor to make 
# 20.6 revolutions (c) Shaft speed if the stepping frequency is 1800 pulses/s
# Page No. 287
# Given data
betaa=2.;               # Step angle
theta=20.6;            # Number of revolutions
fp=1800.;               # Stepping frequency
# (a) Resolution
stepsperrev=360./betaa;      # Speed of machine
# (b) Number of steps required for the rotor to make 20.6 revolutions
steps=theta*360./betaa;
# (c) Shaft speed if the stepping frequency is 1800 pulses/s.
n=betaa*fp/360.;
# Display result on command window
print"\n Resolution =",stepsperrev
print"\n Number of steps required for the rotor to make 20.6 revolutions =",steps
print"\n Shaft speed if the stepping frequency is 1800 pulses/s =",n,"r/s"
 Resolution = 180.0

 Number of steps required for the rotor to make 20.6 revolutions = 3708.0

 Shaft speed if the stepping frequency is 1800 pulses/s = 10.0 r/s

Example E03 : Pg 299

In [3]:
# Example 7.3
# Determine (a) Synchronous speed (b) Rail speed assuming slip of 16.7%
# Page No. 299
# Given data
f=50.;               # Frequency of machine
tau=0.24;           # Pole pitch
s=0.167;            # Slip
# (a) The synchronous speed 
Us=2*tau*f;
# (b) Rail speed assuming slip of 16.7 percent
U=Us*(1-s);
# Display result on command window
print"\nThe synchronous speed =",Us,"m/s"
print"\nRail speed assuming slip of 16.7 percent =",U,"m/s"
The synchronous speed = 24.0 m/s

Rail speed assuming slip of 16.7 percent = 19.992 m/s