Vector control of induction motor description

1. Vector control of
Induction Machine

2. WHY NEED DYNAMIC MODEL?
• In an electric drive system, the machine is part
of the control system elements
• To be able to control the dynamics of the drive
system, dynamic behavior of the machine need
to be considered
• Dynamic behavior of IM can be described
using dynamic model of IM

3. WHY NEED DYNAMIC MODEL?
• Dynamic model – complex due to magnetic
coupling between stator phases and rotor phases
• Coupling coefficients vary with rotor position –
rotor position vary with time

4. a
b
b’
c’
c
a’
Simplified
equivalent stator
winding
ias
Magnetic axis of
phase A
Magnetic axis of
phase B
Magnetic axis of
phase C
ics
ibs
DYNAMIC MODEL, 3-PHASE MODEL

5. Let’s look at phase a
Flux that links phase a is caused by:
• Flux produced by winding a
• Flux produced by winding b
• Flux produced by winding c
DYNAMIC MODEL – 3-phase model

6. vabcs = Rsiabcs + d(abcs)/dt - stator voltage equation
vabcr = Rrriabcr + d(abcr)/dt - rotor voltage equation





































cs
bs
as
abcs
cs
bs
as
abcs
cs
bs
as
abcs
i
i
i
i
v
v
v
v





































cr
br
ar
abcr
cr
br
ar
abcr
cr
br
ar
abcr
i
i
i
i
v
v
v
v
• abcs flux (caused by stator and rotor currents) that
links stator windings
• abcr flux (caused by stator and rotor currents) that
links rotor windings
DYNAMIC MODEL – 3-phase model

7. DC drive analogy

27. Equivalent circuit and phasor diagram
Rotor leakage inductance Llr has been neglected for simplicity , which make the rotor
flux same as air gap flux
Stator current is given by
ids - magnetizing component current and - contributes only the reactive power
iqs – torque component current - contributes active power across air gap

60. According to the shape of the field, synchronous machines may be classified as
cylindrical-rotor (non-salient pole) machines (Figure 1) and salient-pole machines (Figure 2).
Figure 1. Construction of cylindrical-rotor synchronous machine
Figure 2. Salient-pole rotor construction

68. Pull out torque.
It is the maximum
sustained torque
which the motor will
develop at
synchronous speed
for I minute with
rated frequency and
with rated field
current.