What is a fail-safe electric motor brake?

A fail-safe electric motor brake is a spring-set brake that holds the load by spring force when the electrical coil is de-energized. This means the load is held even when power is lost, interrupted or deliberately switched off. When the DC coil is energized, electromagnetic force overrides the spring pressure and releases the friction discs for drag-free rotation. The fail-safe behavior is required in hoists, cranes, vertical lifts and any application where a falling load would be dangerous.

How does a spring-set multiple disc brake work?

A spring-set multiple disc brake uses radially-spaced coil springs between the armature plate and the end plate to keep the friction discs compressed when the coil is off. When the coil is energized, electromagnetic flux pulls the armature against the spring pressure, releasing the discs. On de-energization, the springs push the armature back into contact with the discs, applying the brake. Multiple thin discs provide higher torque in a given envelope than a single thick disc because the total friction contact area is larger.

What coil voltages are available for the electric motor brake?

Standard coil voltages are 24V DC, 48V DC, 90V DC and 190V DC. Custom coil voltages are available on request for OEM applications. The correct voltage is determined by the available DC supply on the machine and by the response time required — higher voltage produces faster engagement for a given coil design.

How is the electric motor brake installed?

The brake ships ready for installation. The keyed bore slides over the standard motor shaft and the brake is bolted to a frame member or, with the optional C-face flange, to the motor face. No special alignment jig or shimming is required. For retrofits, the existing motor shaft does not need to be modified — the same key that drives the load also drives the brake hub.

How does a spring-set electric brake compare to a permanent magnet brake?

A spring-set electric brake is fail-safe: it holds the load by spring force when de-energized, so it holds even during power loss. A permanent magnet brake requires continuous power to hold and releases when power is removed, so it is not suitable for fail-safe holding applications. Spring-set brakes are preferred in hoists, cranes, vertical lifts and anywhere a falling load would be dangerous.

Does Raydafon offer OEM customization on the electric motor brake?

Yes. Raydafon offers OEM customization on coil voltage, torque rating, mounting flange (including C-face non-magnetic), friction disc stack configuration, shaft bore diameter and keyway dimensions. Send the required torque, motor shaft dimensions, available DC voltage and mounting constraints for a quotation. MOQ depends on the specific modification.

What is the lead time and MOQ for the electric motor brake?

Standard configurations ship in 15 to 30 days. MOQ is 1 unit for standard configurations. Custom coil voltages, torque ratings and mounting flanges are confirmed at quotation. Raydafon is based in Ningbo, China and supplies wholesale and OEM quantities worldwide. Payment terms, shipping method and Incoterms are confirmed at order.

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Electric Motor Brake

Q: Can the electric motor brake be mounted directly to a C-face motor?

Yes. An optional C-face non-magnetic flange allows the brake to mount directly to C-frame motors without an adapter plate. The non-magnetic flange isolates the brake's magnetic circuit from the motor end bell, preventing flux leakage that could affect motor performance. With the C-face option, the brake and motor form a single mechanical assembly.

Electric Motor Brake is a spring-set fail-safe multiple disc brake designed for high torque in a compact envelope. The brake uses radially-spaced coil springs to keep the friction discs compressed against the armature when the coil is not energized — this is the "fail-safe" behavior that holds the load when power is removed. When the DC coil is energized, electromagnetic force overrides spring pressure and releases the friction discs for drag-free shaft rotation. Standard coil voltages are 24V, 48V, 90V and 190V DC. The brake ships ready for installation by sliding over the keyed motor shaft and bolting to a frame member. Optional C-face non-magnetic flanges allow direct mounting on C-frame motors without an adapter. Custom coil voltages, mounting flanges and disc stacks are available for OEM applications. Suitable for machine tool spindles, conveyors, hoists, packaging equipment and any application that requires positive holding when power is removed.

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Product Description

Raydafon · EFS Series Electric Motor Brake · Spring-Set Multiple Disc Fail-Safe Design

Electric Motor Brake — Spring-Set Multiple Disc Fail-Safe Brake for C-Face Motor Mounting

The Electric Motor Brake is a spring-set fail-safe multiple disc brake that provides unusually high torque for its compact size. The brake uses radially-spaced coil springs between the armature and the end plate to keep the friction discs compressed against the armature. This produces a constant holding force whenever the coil is not energized — the definition of a fail-safe brake. If power is lost during operation, the brake engages automatically and holds the load.

When the DC coil is energized, electromagnetic force flows through the flux path to override spring pressure and releases the friction discs, allowing drag-free rotation of the shaft. Standard coil voltages are 24V, 48V, 90V and 190V DC. The brake ships ready for installation by sliding the unit over the keyed motor shaft and bolting it to a frame member. Optional C-face non-magnetic flanges allow direct mounting to C-frame motors without an adapter plate.

Brake TypeSpring-Set Fail-SafeMultiple disc design

ActionFail-SafeHolds when de-energized

Coil Voltage24V - 190V DCCustom voltages available

MountingKeyed Shaft / C-FaceSlide-on installation

How a Spring-Set Electric Motor Brake Works

Operating Principle

The operating principle of a spring-set electric motor brake is fundamentally different from a hydraulically or pneumatically actuated brake. Understanding the three-state cycle below is essential to selecting the correct brake for a given application — particularly the fail-safe behavior that makes this brake type the standard for hoists, cranes and any vertical-axis load that must not fall when power is interrupted.

State 01 · De-Energized

Brake Engaged — Springs Hold the Load

With the coil de-energized, radially-spaced coil springs between the armature and end plate push the friction discs into contact with the armature and the shaft hub. The friction engagement holds the shaft against rotation. This is the brake's default state — it does not require any power to hold the load, which is why it is called fail-safe.

State 02 · Energized

Brake Released — Coil Overrides Springs

When DC current flows through the coil, electromagnetic force is generated through the flux path. This force pulls the armature against the spring pressure, releasing the friction discs from contact. With the discs released, the shaft rotates freely without drag. The release force is dimensioned to reliably overcome the spring force plus the friction force at the rated torque.

State 03 · Power Loss

Brake Re-Engages Automatically

If the DC supply is interrupted — whether from a power failure, an emergency stop signal or a deliberate coil de-energization — the coil field collapses within milliseconds and the springs re-engage the friction discs. The load is brought to a controlled stop by the brake torque. This is the fail-safe behavior: no external command or auxiliary power is needed to apply the brake.

Technical Specification — EFS Series Electric Motor Brake

Engineering Reference

The table below lists the standard specification of the Electric Motor Brake. For a replacement or OEM application, confirm the required brake torque, coil voltage, motor shaft diameter and mounting interface against the machine drawing before ordering.

Standard specification — EFS series electric motor brake
Parameter	Specification
Brake Type	Spring-set, fail-safe, multiple disc brake
Operating Principle	Spring pressure holds when de-energized; DC electromagnet releases when energized
Disc Configuration	Multiple friction disc stack with radial coil springs
Standard Coil Voltage	24V DC, 48V DC, 90V DC, 190V DC
Custom Coil Voltage	Available on request for OEM applications
Torque Range	High torque relative to envelope size; specific values confirmed per frame
Engagement Time	Milliseconds after coil de-energization
Release Time	Milliseconds after coil energization
Friction Material	Wear-resistant friction discs suitable for dry running
Armature Material	High magnetic permeability steel for fast response
Coil Insulation	Class F (standard), other classes available
Standard Mounting	Slide over keyed shaft, bolt to frame member
C-Face Mounting	Optional non-magnetic C-face flange for direct C-frame motor mounting
Application Duty	Holding and emergency stop; not intended for frequent dynamic braking cycles without load confirmation
Customization	Coil voltage, torque rating, mounting flange, disc stack, shaft bore
Certification	ISO 9001 manufacturing system
Origin	Ningbo, China

electric motor brake spring set fail safe multiple disc EFS series assembled unit — **Electric Motor Brake — Assembled Unit** The assembled brake shows the coil housing, armature plate, end plate and the mounting bolt holes on the frame member. The keyed bore at the center slides over the motor shaft. The coil leads exit through the housing for connection to the DC supply. The overall envelope is dimensioned to fit within the same footprint as standard C-face motor brake installations.

Why Specify the Raydafon Electric Motor Brake?

Design Advantages

Six design characteristics separate this electric motor brake from a commodity unit. Each one addresses a specific consideration in fail-safe braking applications.

Fail-Safe by Design — No Power Required to Hold

The brake holds the load by spring force, not by electromagnetic force. This means the load is held even when the DC supply is lost, interrupted or deliberately switched off. For hoists, cranes, vertical conveyors and any application where a falling load would be dangerous, this property eliminates the need for a separate backup brake or mechanical lock.

High Torque in a Compact Envelope

The multiple disc design multiplies friction surface area within a small axial envelope. Multiple thin friction discs produce higher torque than a single thick disc of the same outer diameter because the total friction contact area is larger. This is why the brake can deliver unusually high torque without a large housing — a critical advantage in machine designs where axial space is constrained.

Fast Response Time

The armature is manufactured from high magnetic permeability steel, and the coil flux path is dimensioned to minimize the time between coil energization and brake release. Similarly, on de-energization the spring force applies the brake within milliseconds. This fast response is important in emergency stop sequences where the braking distance determines the safety distance of the machine guard.

Slide-On Keyed Shaft Installation

The brake ships ready for installation. The bore is keyed to match the standard motor shaft, so the brake slides over the shaft and bolts to a frame member. No special alignment jig or shimming is required. For retrofits, the existing motor shaft does not need to be modified — the key that drives the driven load also drives the brake hub.

Optional C-Face Flange for Direct Motor Mounting

C-face non-magnetic flanges are available for direct mounting on C-frame motors. The non-magnetic flange isolates the brake's magnetic circuit from the motor end bell and prevents flux leakage that could affect motor performance. With the C-face option, the brake and motor become a single mechanical assembly that mounts to the machine as one unit.

ISO 9001 Manufacturing and Full Traceability

Every brake is assembled under an ISO 9001 quality system. Coil resistance, spring free length, disc thickness and bore concentricity are inspected in process. Each unit receives a functional test — engagement torque and release current — before packing. Batch material certificates are retained and available with the shipment.

electric motor brake internal structure coil spring armature disc stack exploded view — **Internal Structure — Coil, Armature, Disc Stack and Springs** The internal structure shows the coil assembly, the armature plate, the friction disc stack, and the radially-spaced coil springs. When the coil is energized, the magnetic flux pulls the armature plate against the springs and releases the disc stack. When the coil is de-energized, the springs push the armature plate back against the disc stack, engaging the brake. The end plate provides the reaction surface for both the springs and the magnetic flux path.

Where the Electric Motor Brake Is Used

Applications

The EFS Series is specified wherever a fail-safe holding brake is required on an electric motor. The applications below are the ones most often quoted on a Raydafon electric motor brake enquiry.

Hoists & Cranes

Overhead hoists, gantry cranes and jib cranes where a falling load must be prevented when power is removed.

Vertical Conveyors

Bucket elevators, vertical screw conveyors and indexing lifts where the load must be held between cycles.

Machine Tools

Spindle holding brakes, rotary table brakes and index table positioning mechanisms where fast release and repeatable engagement are required.

Packaging Machinery

Cartoners, labellers and wrapping machines where the brake holds the machine at a defined position between cycles.

Door & Gate Drives

Industrial roll-up doors, gates, barriers and shutters where the brake holds the door in position when the drive is de-energized.

Textile Machinery

Winding, unwinding and tension control equipment where the brake provides fast stop and precise holding.

Medical & Laboratory

MRI patient tables, scanner gantries and laboratory automation where the brake must release without drag and hold without drift.

OEM Machine Builds

Wholesale and OEM supply for machine builders who need a standard fail-safe brake integrated into a production line.

Spring-Set Electric Brake vs Other Brake Types

Selection Guide

A common procurement question is how a spring-set electric motor brake compares to other common industrial brake types. The comparison below uses typical values at comparable torque for each type.

Brake type comparison — spring-set electric, permanent magnet, hydraulic, pneumatic
Parameter	Spring-Set Electric	Permanent Magnet	Hydraulic	Pneumatic
Fail-Safe	Yes — holds without power	No — requires power to hold	Yes — spring return	No — requires air pressure
Power Source	DC electrical only	DC electrical only	Hydraulic pump	Air compressor
Response Time	Milliseconds	Milliseconds	Slower (valve + fluid)	Moderate
Torque Density	High (multiple disc)	Moderate	Very high	Moderate
Installation	Slide over keyed shaft, bolt to frame	Integrated in motor design	Requires hydraulic circuit	Requires air line and valve
Maintenance	Disc wear inspection only	Not serviceable	Fluid change, seal replacement	Air filter, seal replacement
Environmental	Unaffected by moisture, dust, temperature	Temperature sensitive	Sensitive to contamination	Sensitive to moisture in air
Best Suited For	Fail-safe holding on electric motors, hoists, cranes, machine tools	Compact motors with integrated brake	Heavy machinery with existing hydraulic power	Applications with existing compressed air

How to Order the Electric Motor Brake

Ordering Inputs

To confirm the correct EFS Series brake and issue a wholesale or OEM quotation, Raydafon needs the five items below. For a replacement unit, the original brake nameplate data, motor nameplate or a dimensioned drawing is usually sufficient.

Send These Five Details for an Electric Motor Brake Quotation

Send the five items below and Raydafon will confirm the model, torque, coil voltage, mounting interface and lead time within one working day.

01Required brake torque (N.m or lb-ft) at the motor shaft
02Motor shaft diameter and keyway dimensions
03Available DC coil voltage (24V / 48V / 90V / 190V or custom)
04Mounting configuration: frame-mounted, C-face motor, or foot bracket
05Quantity required and any environmental constraints (temperature, moisture, dust)

electric motor brake installation C-face flange keyed shaft mounting detail — **Installation Detail — Keyed Shaft and C-Face Flange** The brake slides over the keyed motor shaft and is bolted to the frame member through the mounting holes. For C-face motor mounting, the optional non-magnetic flange bolts to the motor face and the brake bolts to the flange. This isolates the brake magnetic circuit from the motor end bell and prevents flux leakage. The keyed bore transfers brake torque to the shaft without slip.

Talk to Raydafon About Your Electric Motor Brake Requirement

Whether you are replacing a worn fail-safe brake on an existing motor, specifying a new brake for an OEM machine build, or sourcing spring-set electric motor brakes in wholesale volume, Raydafon can quote to your torque, shaft diameter, coil voltage, mounting configuration and environmental requirements. OEM and project quantities supplied directly from the Ningbo factory. ISO 9001 certified.

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