Eddy-Current Brakes

The eddy-current braking principle

When a conductor moves relative to a magnetic field, the changing field induces circulating currents — eddy currents — inside the conductor. Those currents create their own field that opposes the motion that caused them, so the result is a retarding force acting only while there is relative movement. Because the force is set up magnetically across an air gap, nothing rubs and nothing wears; the energy leaves as heat spread through the conductive reaction plate.

Where eddy-current brakes are used

The pattern that suits eddy-current braking is a fast, frequently repeated stop where friction pads would overheat, fade or need constant replacement. That covers a broad span of moving-load duties, from transit and launch systems to industrial handling, and it pairs naturally with linear-motor propulsion where the same contactless, adhesion-independent thinking already applies.

Permanent-magnet vs powered variants

An eddy-current brake needs a magnetic field, and there are two ways to supply it. A powered (electromagnet) variant energises coils, so the field — and therefore the braking force — can be switched and modulated, at the cost of a power supply and control. A permanent-magnet variant uses fixed magnets and needs no external power while moving, which makes it simpler, inherently fail-safe against loss of supply, and well suited to always-available retardation. Our passive product line is built around this approach.

Choosing between them

• Permanent-magnet: no power to brake, fewer failure modes, force shaped by fixed geometry — best where you want dependable, always-on deceleration.
• Powered: on-demand and adjustable braking, at the cost of supply, cabling and control electronics — best where the brake must be commanded on and off or trimmed.

See our permanent-magnet brakes for the passive, no-external-power product and how we tune its behaviour to a given duty.

Dynamic vs holding braking

An eddy-current brake is a dynamic brake: it produces force from relative motion, so its retardation is strong at speed and typically falls away as the load slows, reaching zero at a standstill. That makes it excellent for taking energy out of a moving load, but it cannot hold a stationary vehicle or a load on a grade on its own. Where zero-speed restraint is required, we pair the dynamic brake with a mechanical holding brake that takes over as motion stops.

Why contactless matters

Because there is no physical contact, there are no friction pads to wear out, glaze or fade, and no drive-slip limit tied to how well two surfaces grip — performance stays consistent in rain, ice or on a grade. Maintenance drops to inspecting the reaction plate and gap rather than servicing consumables, and the same brake behaves the same way on its thousandth stop as on its first. The force-speed behaviour can be shaped across the working range by magnet geometry, pole pitch, air gap and reaction-plate material, so within the design envelope the brake can be matched to the duty rather than accepted as-is. We size these systems with equivalent-circuit models, cross-check with FEA, run the full duty in route and thermal simulation, and confirm the plate stays within its thermal limits before any metal is cut.

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