Release (Tripping Element); Time-Current Characteristics (Tripping Characteristics) - ABB MS116 Manual

2.1.1 Release (tripping element)

Manual motor starters fulfill trip classes in accordance with IEC 60947-4-1 and UL 60947-4-1A. The trip class indicates
the maximum tripping time from a cold state. This tripping time refers to a steady symmetrical three-pole load with
a 7.2x current setting.
Similar to molded case circuit-breakers (MCCB), standard manual motor starters are equipped with two releases:
−
An adjustable, inverse time-delay overcurrent release for overload protection
−
A fixed, instantaneous release for short-circuit protection
Magnetic only (MO) manual motor starters are equipped with an instantaneous short-circuit release. When com-
bined with an external overload relay, this wiring schematic closely resembles that of conventional combination
starters (e.g. circuit-breaker, contactor, and overload relay).
In the event of a motor overload, the overload relay trips and the contactor is switched OFF. However, the manual
motor starter magnetic only stays switched ON. The magnetic only manual motor starter trips only in the event of a
short-circuit and clears the fault. Consequently, this starter differentiates between overloads and short-circuits by
means of separate signaling (does not apply to the MS116).

2.1.2 Time-current characteristics (tripping characteristics)

Tripping times in accordance with the harmonized IEC 60947-4-1, UL 60947-4-1A and CSA C22.2 No. 60947-4-1 stand-
ards can be seen in the figures below. The tripping characteristics of the inverse time-delay thermal over-current
release applies for direct current (DC) and alternating current (AC) with frequencies of 50/60 Hz.
For three-pole loads and currents of between 3 - 8 times the set current, the tolerance of the tripping time is ±20 %.
The tripping characteristics of the instantaneous short-circuit releases is based on the rated operational current I
which, in the case of the manual motor starter is the same as the upper value of the setting range. Lower current set-
tings result in a higher multiple for the tripping current of the instantaneous short-circuit releases. The tripping
characteristic curves are valid for the cold state; and the warm state, while the tripping times of the inverse time-
delay thermal over-current release have a higher spread.
Tripping curves for manual motor starters are easily accessible at ABB's Download Center.
https://library.abb.com/ > All Categories > Products > Low Voltage Products and Systems > Control Product > Manual Motor Starters
APR I L 19
MA N UA L MOTOR START ER G UI D E
Figure 3: Tripping diagram for the MSx and MOx.
,
e
1 4/ 80