Inertia stop and brake stop in inverter control

Inverter inertia parking is one of the inverter stop methods and the other method is called braking stop.

1. Inverter free stop

Inertia stop is free stop. After the inverter stops output immediately by turning off the power supply, cutting off the operation control signal, etc., the motor continues to slide with the inertia generated by its own operation until it stops rotating. This method will not generate feedback voltage inside the inverter.

After the inverter receives the shutdown command, it immediately stops output and the load stops freely according to mechanical inertia. The inverter stops by stopping output. At this time, the power supply of the motor is cut off, and the traction system is in a free braking state. Since the length of the stop time is determined by the inertia of the traction system, it is also called inertia stop.

The inverter stops by stopping the output. At this time, the power supply of the motor is cut off and the traction system is in a free braking state. Since the length of the stop time is determined by the inertia of the traction system, it is called inertia stop. When stopping by inertia, you should pay attention not to start when the motor is not really stopped. If you want to start, you should brake first and then start after the motor stops. This is because the difference between the motor speed (frequency) and the inverter output frequency at the moment of starting is too large, which will cause the inverter current to be too large and damage the power tube of the inverter.

2. Inverter braking stop

Braking stop is slope parking. Braking stop is divided into DC braking, power braking, feedback braking, mixed braking, brake mechanical braking and other methods.

The selection of the inverter's parking method is related to the parking time required on site. Usually, when the parking time requirement is less than the free parking time, braking deceleration stop is selected.

DC braking (that is, supplying a certain amount of DC power to the power grid); dynamic braking (using resistance to consume energy); mixed braking (DC braking + dynamic braking); regenerative braking (injecting the generated current into the power grid); mechanical braking with brake.

Stopping is divided into ramp stop and free stop (fast stop is also ramp stop, but the ramp is steeper).

Braking also includes mechanical braking (such as brake), energy consumption braking (brake resistor, reverse braking, DC braking, etc.), regenerative braking, etc. Whether braking is needed depends on the operating state of the motor. When the required stop time is less than the free stop time during ramp stop, braking is required; braking is sometimes required when the motor is running normally, such as when the hook is lowered.

In the drive system composed of power grid-inverter-motor-load, energy can be transmitted in both directions. When the motor is in the motor working mode, the electrical energy is transmitted from the power grid to the motor through the inverter, converted into mechanical energy to drive the load, and the load therefore has kinetic energy or potential energy; when the load releases this energy in order to change the state of motion, the motor is driven by the load and enters the generator working mode, converting the mechanical energy into electrical energy and feeding it back to the previous inverter. This feedback energy is called regenerative braking energy, which can be fed back to the grid through the inverter or consumed in the braking resistor on the inverter DC bus (energy consumption braking).

Occasions where braking energy is generated

1. The process of lowering heavy objects in lifting equipment

2. The process of rapid deceleration of large inertia loads

3. The process of lowering the donkey head of a walking beam pump