Danfoss FC 300 Design Manual

Also see for FC 300: Operating instructions Instruction manual Design guide Design guide Design guide

Contents

Danfoss FC 300 Design Manual Manual pdf 51 page image

3.8.2. Hoist Mechanical BrakeThe VLT Automation Drive FC 300 features a mechanical brake control specifically designed forhoisting applications. The hoist mechanical brake is activated by choice [6] in par. 1-72. The maindifference compared to the regular mechanical brake control, where a relay function monitoringthe output current is used, is that the hoist mechanical brake function has direct control over thebrake relay. This means that instead of setting a current for release of the brake, the torqueapplied against the closed brake before release is defined. Because the torque is defined directlythe set-up is more straightforward for hoisting applications.By using the Proportional Gain Boost (par. 2-28), a quicker control when releasing the brake canbe obtained. The hoist mechanical brake strategy is based on a 3-step sequence, where motorcontrol and brake release are synchronized in order to obtain the smoothest possible brake re-lease.3-step sequence1. Pre-magnetize the motorIn order to ensure that there is a hold on the motor, and to verify that it is mountedcorrectly, the motor is first pre-magnetized.2. Apply torque against the closed brakeWhen the load is held by the mechanical brake, its size cannot be determined, only itsdirection. The moment the brake opens, the load must be taken over by the motor. Tofacilitate the takeover, a user defined torque, set in par. 2-26, is applied in hoisting di-rection. This will be used to initialize the speed controller that will finally take over theload. In order to reduce wear on the gearbox due to backlash, the torque is ramped up.3. Release brakeWhen the torque reaches the value set in par. 2-26Torque Ref, the brake is released.The value set in par. 2-25Brake Release Time determines the delay before the load isreleased. In order to react as quickly as possible on the load-step that follows upon brakerelease, the speed-PID control can be boosted by increasing the proportional gain.3.4: Brake release sequence for hoist mechanical brake control3.8.3. CablingEMC (twisted cables/shielding)FC 300 Design Guide 3. Introduction to FC 300MG.33.B9.22 - VLT® is a registered Danfoss trademark. 513