
MANUAL MOTOR STARTER GUIDE
APRIL 19
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The greatest risk for applications such as motors is over-
heating. Abnormal temperature rises can be caused by
overloads, electrical faults, cooling problems or improper
operating parameters or operation conditions. This differ-
entiates motors and pumps from other applications, such as
heating resistors or lamps.
Examples of such overloads include:
Overloads caused by over current
–
locked rotors
–
long starting or braking times
–
changes of the friction ratio of the operated engine
–
non-permissible intermittent operations
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long-term overloads in continuous operation
–
undervoltage
Supply problems, which could cause unsymmetrical over-currents
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earth faults
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phase loss
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phase unbalance on the supply side
–
interwinding or interturn fault within the motor
Cooling problems
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reduced convection currents due to dust or dirt
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mounting position of the motor: good circulation of air prevents heat build-up
–
low air density due to incorrect installation and altitude environmental parameters