There are two types of inverter parking.

One form is called "free parking". As the name implies, it is to quickly "power off" the motor, and let the motor coast to stop by its own inertial force (OFF2 stop);

Another form is called "brake parking". Then this "brake to stop", there are more ways. For example, OFF1 parking means stopping at a certain ramp deceleration, or OFF3 "emergency braking" parking (stopping according to the motor's limit braking capacity).

Inverter free stop

Inertial parking is free parking. After turning off the power supply, cutting off the operation control signal, etc., the inverter immediately stops output, the motor will continue to slide with the inertia generated during its operation until it stops. This method will not generate feedback voltage to the inverter.

Our door is set to free stop, forward and reverse rotation, and then run to 50HZ, three seconds after parking, reverse 50HZ, there will be a current limit, and no over-current is reported. Can this current be limited? How much current is there? I reported overcurrent when I tested it. Note, the inverter is equipped with a motor, and the motor is unloaded. More than 30 currents in normal operation.

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

The inverter stops by stopping the output. At this time, the power of the motor is cut off, and the drag system is in a free braking state. Since the length of the parking time is determined by the inertia of the drag system, it is called inertial parking. It should be used during inertial parking. Note that the motor should not be started when it has not really stopped. If you want to start, you should brake first and start after the motor has stopped. This is because the motor speed (frequency) at the moment of starting is too far from the output frequency of the inverter, which will cause the frequency conversion Excessive current of the inverter damages the power tube of the inverter.

Inverter brake to stop

Braking parking is a slope parking. Braking parking is divided into DC braking, dynamic braking, feedback braking, hybrid braking, and mechanical braking with brake.

The parking mode selected for the inverter is related to the parking time required on site. Normally, when the parking time requirement is less than the free stop time, select braking to decelerate to stop.

DC braking (that is, a certain amount of direct current is supplied to the electricity); dynamic braking (energy consumption by resistance); hybrid braking (DC braking + dynamic braking); feedback braking (injecting the generated current into the grid); holding brake Mechanical brake.

Parking is divided into ramp parking and free parking (fast parking is also ramp parking, but the ramp is steeper).

Braking also includes mechanical braking (such as holding brake), dynamic braking (brake resistance, reverse braking, DC braking, etc.), feedback braking, etc. Whether or not braking is required is related to the running state of the motor. In ramp parking, when the required parking time is less than the free parking time, braking is required; sometimes when the motor is running normally, braking is sometimes required, such as when the hook is lowered.

Working mode of resistance energy consumption braking

The method used for resistance energy consumption braking is the braking unit and the braking resistor, that is, the electric energy is consumed in the high-power resistor through the built-in or external braking resistor to realize the four-quadrant operation of the motor. Although this method is simple, it has the following serious disadvantages.

(1) Simple energy-consumption braking sometimes cannot suppress the pump voltage generated by rapid braking in time, which limits the improvement of braking performance (large braking torque, wide speed range, good dynamic performance)

(2) Waste energy and reduce the efficiency of the system

(3) The resistance heating is serious, which affects the normal operation of other parts of the system

Supporting brake mode: the electric motor drives large inertia loads (such as centrifuges, gantry planes, road vehicles, large and small vehicles, etc.) and requires rapid deceleration or parking; electric motors drive potential loads (such as elevators, cranes, mine hoists, etc.) Motors, etc.); motors are often in a state of being dragged (such as centrifuge auxiliary machines, paper machine guide roller motors, chemical fiber mechanical drafting machines, etc.). The common characteristics of the above types of loads require that the motor not only run in an electric state (1 , Three-quadrant), and must run in the power-generating braking state (two and four-quadrant)

In the drive system consisting of power grid-frequency converter-motor-load, energy can be transferred in both directions. When the motor is in the motor working mode, the electrical energy is transferred from the grid to the motor via the frequency converter, and converted into mechanical energy to drive the load. Therefore, the load has kinetic energy or potential energy; when the load releases this energy to change the state of motion, the motor is driven by the load and enters The generator working mode converts mechanical energy into electrical energy and feeds 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's DC bus (energy-consumption braking).

Where braking energy is generated

1. The rapid deceleration process of large inertia load

2. Decentralization process of lifting equipment

3. The lowering process of the donkey head of the beam pumping unit