MCCB for motor protection — 100 A frame, ETU350M trip unit
The overcurrent release is an ETU350M, which provides adjustable thermal-magnetic or electronic protection curves depending on the trip unit variant. Breaking capacity is the headline figure here: 330 kA at 240 V, 242 kA at both 415 V and 440 V, 187 kA at 500 V, and 52.5 kA at 690 V. The SCCR headroom means you can place this upstream of lower-rated branch devices without worrying about cascading failure. Maximum power dissipation is 75 W at rated load, so account for that heat in enclosure sizing.
Selectivity and coordination
For a panel designer or site electrical engineer, the key coordination question is whether this breaker selectively coordinates with downstream devices. The 330 kA at 240 V rating provides full selectivity with most 18 kA or 25 kA branch MCCBs and molded case switches, provided the trip curves are properly set. The ETU350M electronic trip unit allows adjustment of long-time pickup, short-time pickup, and instantaneous settings — essential for achieving Type 2 coordination with contactors and motor starters. The undervoltage release adds a layer of safety: if control power drops, the breaker opens, preventing automatic restart on power restoration.
Auxiliary contacts and alarm switch
That gives you three independent signal paths for status feedback — one pair for the main contact position, one for the alarm contact that changes state only on a trip event (not manual open). Useful for PLC or SCADA integration: wire the alarm contact to a digital input to capture trip events separately from normal on/off status.