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Prevent shaft rotation during power-off with an electromagnetic brake-equipped stepping motor

Case study

Stepping motor with brake

Prevent shaft rotation during power-off
with an electromagnetic brake-equipped stepping motor

Stepping motor with brake

Problem

In material handling equipment, if an external force is applied while the power is off, the motor rotates unintentionally, causing misalignment.

Solution

A power-off activated electromagnetic brake mounted on the stepping motor physically locks the shaft, preventing rotation during power loss.

Benefits

  • Prevents unintended misalignment while the motor is stopped with the power off.
  • Prevents equipment failure caused by unintended misalignment.
  • Reduces the number of parts with an integrated brake design.

"Backdriving": unintended motor rotation in a power-off state

A stepping motor generates a magnetic field by drawing electric current, which holds the shaft in place. When the current stops, the magnetic field disappears, and the motor simultaneously loses its holding torque. If an external pressure is applied in this state, the resulting force or vibration causes the motor shaft to rotate unintentionally. This phenomenon is known as "backdriving.“
When backdriving occurs, the stationary motor shifts out of position. This can prevent a smooth restart, as position adjustments or homing operations are required when power is restored. Furthermore, the unintended rotation can affect other components, potentially leading to severe equipment failure.

A magnetic field is generated when current flows through the stator coils

A magnetic field is generated when current flows through the stator coils

Stopping rotation with an electromagnetic brake

To ensure the shaft stops securely even during a sudden power loss, some motors feature an integrated electromagnetic brake. MinebeaMitsumi's electromagnetic brake-equipped models utilize a power-off activated design. This means the brake engages when the power is disconnected.

Motor power on
Motor power off

When the brake engages, the force of an internal spring physically locks the motor's rotation shaft, stopping any movement. When current is applied, an electromagnetic force is generated that overcomes the spring force, unlocking the shaft and allowing the motor to rotate.

While the word "brake" often brings to mind a dynamic brake used to decelerate moving objects, this electromagnetic brake is a holding brake designed to keep stationary objects securely in place. It is ideal for applications requiring load holding during power-off states.

♦ Vertical transport equipment: with and without an electromagnetic brake during power loss

  • Motor without brake
  • during power loss

Without a brake, a loss of current means losing holding torque, causing the transported load to fall.

Without a brake, a loss of current means losing holding torque, causing the transported load to fall.
  • Motor with brake
  • during power loss

A brake-equipped motor holds its position even when current is lost, preventing the load from falling.

A brake-equipped motor holds its position even when current is lost, preventing the load from falling.
  • Motor with brake
  • Normal operation

During normal operation, the brake is released, allowing vertical load transport.

During normal operation, the brake is released, allowing vertical load transport.

Our stepping motors featuring an integrated brake help decrease the total number of parts and save space.

Please feel free to contact us regarding small-lot orders and customizations.

Related page

Product information

Brake type

Technical information

Wiring diagram and switching sequence

Conversion factors

Notice and cautions -Hybrid stepping motor-

Numbering system

Rotary components case studies

Detecting stepping motor stalls

Stepping motor

Detecting stepping motor stalls

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