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Inverter-driven brake-motor engages instantly

08 August, 2013

The Italian motor-maker Carpanelli has developed an inverter-driven brake-motor that, unlike traditional brake-motors, provides instantaneous brake engagement because it is activated directly by the inverter. The MAI motor is said to cut installation time and costs because there is no need to connect a separate power supply.

On a traditional inverter-driven brake-motor, the brake is activated by an external power supply, which introduces a delay. In the new design, a failsafe, spring-applied, electromagnetic brake is activated by the inverter. No external signal is needed because the brake is wired directly into the terminal box.

The inverter powers both the motor and the brake. By adjusting the inverter parameters, the motor’s performance characteristics can be altered to suit the application. 

The design is said to result in increased braking accuracy and control, and is particularly suitable for applications involving lifting and lowering.

The brake is designed to be powered by a PWM (pulse width modulation) supply with a square-wave output. Conventional AC electromagnetic brakes are usually designed to operate from fixed-frequency supplies are not suitable for variable-frequency supplies.

The new brake has specially designed windings that allow it to produce stable magnetic flux and to operate with a variable frequency. When powered by a three-phase 400V inverter, there are two operating modes:

Carpanelli's brake-motor does not need a separate power supply for the brake

♦  If the inverter frequency is set to 50Hz, and the motor and brake are connected in a star configuration, the motor will provide constant torque up to 50Hz, and constant power, but decreasing torque, up to 85Hz. The brake operates with a constant magnetic field from 5–85Hz.

♦  If the inverter frequency is set to 87Hz, and the motor and brake are connected in a delta configuration, the motor will deliver constant torque up to 87Hz, and constant power, but decreasing torque, up to 145Hz. The brake operates with a constant magnetic field from 5–145Hz.

With a single-phase 230V inverter, and the motor and brake connected in a delta arrangement, the frequency is set at 50Hz.

If, for any reason, the motor is not operated via an inverter, the MAI motor will operate like a normal brake-motor.

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