Motor, System And Soft Starter Protection Mechanisms; Motor Overload Protection - AuCom MVS0080 Product Manual

OPERATION: OPERATION
9.3

Motor, System and Soft Starter Protection Mechanisms

9.4

Motor Overload Protection

710-03261-00D
The MVS incorporates extensive protection features to ensure safe operation of the
motor, system and soft starter. Most protection features can be customised to suit
the installation. Use parameter group 3 to control the situation where the
protections will activate and parameter group 21 to select the soft starter's
response. The default response is to trip the soft starter.
The MVS offers two forms of motor overload protection:
•
a motor thermal model that monitors the performance of the motor and
calculates its status at all times. This protection is based on the motor
information programmed in parameter group 1, and the thermal model adjusts
itself according to the motor's recent operating history (including temperature
rise from previous operation). This model provides finer motor protection than
the time-overcurrent model, if the programmed motor information is accurate.
•
a time-overcurrent model that calculates the motor's status according to a
predefined performance curve. This method is based on IEEE standard
C37.112-1996 ( Inverse-Time Characteristic Equations for Overcurrent Relays )
and provides similar protection to a relay. This model may suit users familiar
with time-overcurrent protection models, but provides coarse motor protection.
The two methods offer similar kinds of protection and we recommend using only
one of the two methods.
NOTE
The soft starter can only be protected from short circuits by suitably
selected R Rated fuses.
Motor failure curve
Motor thermal model
protection curve
Time-overcurrent
protection curve
Typical motor
operating current
Motor current
Motor
service factor
42
Locked rotor
current
MVS Series