Eaton HMCP400W5C Motor Circuit Protector

The Eaton HMCP400W5C is a magnetic‑only circuit breaker (motor circuit protector) designed for use in motor branch circuits. It provides instantaneous short‑circuit protection while allowing the motor starting current to pass without nuisance tripping. The HMCP is intended to be used in series with a contactor and a separate overload relay to form a complete motor starter. This 400 A unit is rated for 600 VAC and features an adjustable magnetic trip mechanism.

Key Features

• Frame rating: 400 A continuous

• Voltage: 600 VAC maximum, 50/60 Hz

• Magnetic trip only – no thermal overload element

• Adjustable instantaneous trip setting: 5x to 10x of the continuous current rating (field adjustable)

• Interrupting rating: 65 kA at 480 VAC, 25 kA at 600 VAC (UL489)

• Three‑pole construction with common trip

• Compact design for panel mounting or direct connection to contactor

• Line and load terminals accept copper or aluminum conductors

• UL489 listed as a motor circuit protector (MCP)

Technical Specifications

Principle of Operation

The HMCP400W5C contains a solenoid mechanism that reacts to high fault currents. When the current exceeds the magnetic trip setting, the solenoid pulls in and trips the breaker instantaneously, disconnecting the circuit. Because it has no thermal element, it will not trip on overloads; this function is delegated to an external overload relay. This separation allows precise coordination between short‑circuit protection and overload protection, meeting NEC requirements for motor circuits.

Applications

• Individual motor branch circuits in industrial control panels

• Motor control centers (MCCs) with separate overload relays

• Compressor, pump, and fan starters

• HVAC equipment requiring high fault current ratings

Installation and Coordination

The HMCP is typically mounted directly upstream of a contactor. The magnetic trip setting must be selected to allow the motor’s locked rotor current (typically 6‑8x FLA) to flow without tripping, yet trip on higher short‑circuit currents. Coordination with upstream feeders can be achieved by selecting appropriate trip settings and ensuring the interrupting rating is sufficient for the available fault current.

The Eaton HMCP400W5C is a reliable, code‑compliant solution for protecting motor circuits against short circuits while maintaining flexibility in overload protection.