Hydraulic-Magnetic Circuit Breakers

Hydraulic-Magnetic Circuit Breakers Technology

Heinemann® patented the first hydraulic-magnetic circuit breaker in1932, and its current product range continues to deliver unparallel circuit protection in environments where nuisance tripping caused by temperature changes, shocks and vibrations are commonplace

Getting to know hydraulic-magnetic circuit breakers

As with all circuit breakers, hydraulic-magnetic circuit breakers protect electrical circuits from damage due to overcurrent, overload, or short circuits. Their primary function is to halt the current flow once a fault is identified. The technology behind Heinemann hydraulic-magnetic circuit breakers, in addition to being reliable and precise, consistently delivers electrical protection in extreme environments, high power surge conditions, and applications ranging from manufacturing to data centers and transport.

Principle of operation

The key difference from other breakers, particularly thermal-magnetic ones, is that they operate solely on the magnetic force generated by the load current passing through a solenoid coil. Ambient temperature does not affect the mechanism, making it ideal for various applications.

Normal operation

Moderate overload condition

The load current is at or below the nominal rating of the breaker. The core remains at the (left) end of the tube opposite the armature. 1. Tube 2. Core 3. Spring 4. Fluid 5. Frame 6. Coil (sensor) 7. Pole piece 8. Armature

The current is sufficient to create enough magnetic flux to move the core (to the right) compressing the springs slightly.

Overload condition

Short-circuit condition

The magnetic flux is sufficient to move the core completely to the end of the tube (right) which attracts the armature and trips the breaker.

The flux produced by the coil alone, regardless of the core position, is sufficient to attract the armature causing the breaker to trip. This circuit interruption occurs with no intentional delay.

Overview of Eaton HMCBs

Our HMCBs have the following features:

Large operating temperature range of -40°C to 85°C and -40°F to 185°F
High inrush tolerance up to 25x
Resistance to shocks and vibrations
Resistance to humidity and corrosion
Immediate resetting after trip
Multiple industry and quality certifications

HMCB elements

More information on features and operation description can be found by clicking on the 'hot spots' on the image below.

Suitable applications for HMCBs

High temperature variance

When equipment is used outdoors or when temperature cannot be controlled.

High inrush current

Suitable for protecting equipment with high starting currents, such as motors, to prevent unnecessary tripping.

Sensitive equipment

Perfect for applications requiring precise tripping points or protection of sensitive equipment.

Shocks and vibrations

Designed to withstand conditions with significant shocks and vibrations.

Inaccessible electrical panel

Compatible with our Remote Breaker Reset for use in hard-to-reach electrical panel locations.

Outdoor locations

Reliable in humid, wet, and dusty environments.

Dark environments

Features an illuminated handle for use in low-light conditions.

See application examples

Eaton is an intelligent power management company dedicated to improving the quality of life and protecting the environment for people everywhere. We are guided by our commitment to do business right, to operate sustainably and to help our customers manage power ─ today and well into the future. By capitalizing on the global growth trends of electrification and digitalization, we’re accelerating the planet’s transition to renewable energy and helping to solve the world’s most urgent power management challenges.

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Hydraulic-Magnetic Circuit Breakers Technology

Getting to know hydraulic-magnetic circuit breakers