Specific steps for the electromechanical braking method of the leveling machine.

When the leveling machine's motor begins to decelerate, it enters a regenerative braking state. The mechanical energy stored in the drive system is converted into electrical energy and fed back to the DC bus through the inverter in the frequency converter. At this point, the inverter operates in rectifier mode. As it absorbs this energy, the voltage across the filter capacitor in the DC link rises, generating what is known as pump-back voltage.

When this voltage exceeds the upper threshold of approximately 690V, the braking chopper circuit is activated. Current flows through the braking resistor connected in parallel with the filter capacitor, dissipating the electrical energy as heat. Consequently, the pump-back voltage drops and the circuit is disconnected once it reaches the preset lower threshold of approximately 680V.

By continuously sampling the pump-back voltage, the braking chopper repeatedly switches on and off, allowing the system to complete dynamic braking. During this process, the IPC-DR braking chopper and its matched braking resistor play a crucial role: it employs an automatic voltage tracking method with a response time of less than 1ms and an operating voltage of 690V DC with a tolerance of ±2V, demonstrating excellent performance.

As the motor enters the crawling phase, if the frequency converter's output frequency falls below the DC braking activation frequency, the converter will initiate the DC braking function. It injects direct current into the stator windings of the induction motor to produce a dynamic braking effect.

At this stage, the output voltage gradually drops to the DC braking voltage. After a brief delay, the DC braking duration timer starts. The output frequency of the converter drops to zero, and the stator's magnetic field stops rotating. The rotating rotor cuts through this stationary DC magnetic field, generating a braking torque that brings the system to a precise stop.

The frequency converter parameters related to DC braking for the leveling machine are set as follows:

DC braking activation frequency (Pr.10): 0.8 Hz
DC braking duration (Pr.11): 0.3 s
DC braking voltage level (Pr.12): Set to 2%, as the motor is a variable-frequency motor.