DIFFERENCES BETWEEN VSI
AND CSI
To understand in easy way the below table provides the differences between VSI and CSI
VSI
|
CSI
|
VSI is used to fed impressed voltages
|
CSI is used to fed the impressed
currents
|
Load commutation is not possible
|
Both forced and load commutations are
possible
|
Open loop and closed loop operations
are possible
|
Only closed loop control is possible
|
Voltage with variable frequency is fed
to synchronous motor
|
The current with variable frequency is
fed to synchronous machine
|
The efficiency is medium
|
The efficiency is high
|
These drives are suitable for low,
medium power applications
|
These drives are suitable for medium
and high power applications
|
Multimotor operation is possible
|
Multimotor operation is not possible
|
Pulse Width Modulation( PWM) technique
is used to reduce the problems of harmonic content, torque pulsations, motor
heating etc.
|
The PWM technique is not used in CSI
so the distortions in the output are more.
|
It gives good and satisfactory behavior in transient
and dynamic state.
 |
Poor dynamic behaviour
 |
DIFFERENCES BETWEEN SEPARATED CONTROL AND SELF CONTROL
Separate control
|
Self control
|
Separate control is the open loop control fed to synchronous
motor
|
Self control is the closed loop
control fed to synchronous motor
|
The supply frequency of stator is
controlled by oscillator
|
Supply frequency changed based on the
rotor speed
|
Synchronous speed and rotor speed are
not equal some difference exist between them
|
At all operating points synchronous
speed and rotor speed are not equal
|
Poor dynamic behavior, problems of
hunting, oscillations and instability
|
Free from hunting problems and have
better stability behavior
|
It is similar to conventional motor
|
It is also known as commutator less
motor
|
VSI are used to provide variable
frequency at open and closed loop conditions
|
CSI are used to provide variable
frequency only for closed loop operations
|
It is applicable for low speeds,
textile industry, fibre, paper and spinning mills
|
It is applicable for pumped storage
water plants and for starting large synchronous machine in gas turbines.
|
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