Induction motor drive Performance characteristics Torque speed characteristics

1. PRESENTATION OF
INDUSTRIAL DRIVES
PRESENTER:
• Bilal Khan (19 EL 61)
• Ateeq Ahmed (19 EL 13)
• Sultan Siyal (19 EL 09)
• Faizan Memon (19 EL 03)
ASSIGNED BY:
• Prof. Dr. Aslam Pervez Memon
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2. TOPICS
1)Induction Motor Drives.
2)Performance Characteristics.
3)Torque–Speed Characteristics.
4)Example 15.1
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3. AC Drives
 AC motor Drives are used in many industrial and domestic
application, such as in conveyer, lift, mixer, escalator etc.
 There are four types of ac drives:
1. Induction motor drives.
2. Synchronous motor drives.
3. Stepper motor drives.
4. Linear induction motor drives.
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4. Induction Motor Drives
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 Three-phase induction motor are commonly used in
adjustable-speed drives (ASD).
 Basic part of three-phase induction motor
1. Stator
2. Rotor
3. Air gap

5. Induction Motor Drives
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• The speed of rotation of field is called the synchronous
speed, which is defined by:
ωs = 2ω/p
or
Ns=120*f/p
where,
ws= syncronous speed [rad/sec]
ω = supply frequency .
P =Number of poles.
Ns is the synchronous speed(rpm)

6. Induction Motor Drives
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Motor Speed (ωm):
 The rotor speed or motor speed is
ωm=ωs(1-S)
Where S is slip, defined as:
s = ωs - ωm / ωs
or
s=Ns-Nm / Ns
 Rotor electrical speed (ωre) of the rotating field.
ωre = p*ωm/2
Where,
ωs=syncronous speed [rad/sec]
Ns= syncronous speed [rpm]
ωm=motor speed [rad/sec]
Nm is motor speed [rpm]

7. Equivalent Circuit of Induction Motor
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8. TYPES OF LOSSES IN INDUCTION MOTOR
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9. Performance Characteristics OF I.M
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Stator copper loss :
Rotor copper loss :
Core losses:

10. Performance Characteristics OF I.M
• Gap power (power passing from the stator to the rotor
through the air gap):
• Power developed by motor:
• Developed torque:
OR
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11. Performance Characteristics OF I.M
Input power of motor.
Output power of motor.
Efficiency:
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12. Performance Characteristics OF I.M
• If Pg >> (Pc + Psu) and Pd >> Pno load,
• The efficiency becomes approximately:
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13. Performance Characteristics OF I.M
• Generally, value of reactance magnetization Xm >> value
Rm (core losses)
• So, the magnetizing voltage same with the input voltage :
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14. Performance Characteristics OF I.M
 The input impedance of the motor becomes:
 Power Factor (PF) angle of the motor:
 Rms Rotor Current:
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15. Performance Characteristics OF I.M
• Torque Developed (Td):
Substituting (Ir′) from Eq. (15.17) in Eq. (15.9) and then Pg
in Eq. (15.12a) yields:
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16. Torque–Speed Characteristics of
Induction Motor
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17. Torque–Speed Characteristics of
Induction Motor
 Near the synchronous speed, that is at low slips, the torque is
linear and is proportional to slip.
 Beyond maximum torque (breakdown torque), the torque is
inversely proportional to slip.
 At standstill, the slip equals unity, and the torque produced is
known as standstill torque.
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18. Torque–Speed Characteristics of
Induction Motor
Operating Regions of Induction Motor:
1. Motoring or Powering region.
2. Regeneration (s < 0) region.
3. Braking or Reverse Plugging.
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19. Torque–Speed Characteristics of
Induction Motor
 Starting torque of motor: ωm = 0 and s = 1.
By putting s=1 in Eq. (15.18) we get:
 Slip for maximum torque (sm): dTd/ds=0 in Eq. (15.18)
 Maximum Developed torque (pull-out or breakdown torque:
put (s = sm) in Eq. (15.18)
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20. Torque–Speed Characteristics of
Induction Motor
• Maximum regenerative torque: (s = -sm) in Eq. (15.18)
where,
s=-sm is slip of motor
• For motors of more than 1-kW rating:
Rs is considered small compared with other circuit impedances:
Torque of Motor:
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21. Torque–Speed Characteristics of
Induction Motor
The speed and torque of induction motors can be varied by one
of the following means.
1. Stator voltage control.
2. Rotor voltage control.
3. Frequency control.
4. Stator voltage and frequency control.
5. Stator current control.
6. Voltage, current, and frequency control.
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22. Example 15.1
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23. Example 15.1
(a) The synchronous speed ωs:
From Eq. (15.1)
ωs = 2ω/p = 2 * 377/4 = 188.5 rad/s.
(b) The slip(s):
From Eq. (15.4)
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24. Example 15.1
,
(c) The input current (Ii);
From Eq. (15.15),
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25. Example 15.1
(d) The input power Pi;
From Eq. (15.13),
(e) The input PF of the supply, PFs:
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26. Example 15.1
(f) the gap power Pg;
From Eq. (15.17), the rms rotor current is
From Eq. (15.9),
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27. Example 15.1
(g) the rotor copper loss (Pru):
(h) the stator copper loss Psu:
(i) the developed torque Td:
From Eq. (15.12a),
Td = 22,327/188.5 = 118.4 N-m.
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28. Example 15.1
(j) the efficiency:
Po = Pg - Pru - Pno load
Po= 22,327 - 625 - 60 = 21,642 W= 21642/ 23482=
(k) the starting current Irs and starting torque T.
For s = 1, Eq. (15.17) gives the starting rms rotor current
From Eq. (15.19),
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29. Example 15.1
(l) the slip for maximum torque sm:
From Eq. (15.20), the slip for maximum torque (or power)
(m) the maximum developed torque in motoring, Tmm
From Eq. (15.21), the maximum developed torque
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30. Example 15.1
From Eq. (15.22), the maximum regenerative torque is
(n) the maximum regenerative developed torque Tmr:
(o) Tmm and Tmr if Rs is neglected.
From Eq. (15.25)
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31. Example 15.1
From Eq. (15.26),
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