Applications
3.3 Motor protection applications of 3VA molded case circuit breakers
3VA molded case circuit breakers with IEC certificate
Manual, 03/2019, A5E03603177010-03
149
3.3.2.1
3VA2 motor protection circuit breaker up to 500 A, tested according to
IEC EN 60947-4-1
As the 3VA2 molded case circuit breakers have been tested according to standard
IEC EN 60947-4-1 (as motor starters), these devices can also be used as motor protection
circuit breakers without an additional contactor. In this case the 3VA2 motor protection
breaker takes on the short-circuit protection and overload protection functions in addition to
functional switching (ON/OFF) of the motor.
However, as functional switching of the motor according to utilization category AC-3 reduces
the electrical service life of the circuit breaker, this use is only suitable for applications with a
low switching frequency. The maximum adjustable rated current of the circuit breaker is also
restricted by the increased AC-3 requirements.
Dependence of motor protection circuit breaker on motor size and electrical service life
1)
Guide value for 4-pole standard motors at 400 V AC, 50 Hz. Selection depends on the specific startup and rated
data of the protected motor
2)
Rated conditional short-circuit current:
•
l
q
= 55 kA - circuit breaker with medium breaking capacity M
•
l
q
= 85 kA - circuit breaker with very high breaking capacity C
