Feedback to the unit supplier: Inertial parking of the frequency converter is one of the parking methods for the frequency converter, and the other method is called braking parking.
Free parking of frequency converter
Inertial parking, also known as free parking. After immediately stopping the output of the frequency converter by turning off the power supply, cutting off the operation control signal, etc., the motor continues to slide with the inertia generated during its own operation until it stops rotating. This method does not generate feedback voltage inside the frequency converter.
Our door is equipped with free parking, rotating forward and backward, and then running to 50HZ. After stopping for three seconds, reversing to 50HZ will result in current limiting and no overcurrent reporting. Can this current be limited? How much current is there? I reported an overcurrent during testing. Explanation: The frequency converter is equipped with a motor, and the motor is unloaded. Normal operation with a current of over 30.
After receiving the shutdown command, the frequency converter immediately stops outputting and the load stops freely according to mechanical inertia. The frequency converter shuts down by stopping the output. At this point, the power supply to the motor is cut off, and the drive system is in a free braking state. Since the length of the shutdown time is determined by the inertia of the drive system, it is also known as inertia shutdown.
The frequency converter stops the output and stops the vehicle. At this time, the power supply to the motor is cut off, and the drive system is in a free braking state Due to the fact that the length of parking time is determined by the inertia of the towing system, it is called inertial parking During inertia parking, attention should be paid not to start the motor before it has truly stopped. If you want to start, brake first and wait for the motor to stop before starting This is because the difference between the motor speed (frequency) at the moment of starting and the output frequency of the frequency converter is too large, which can cause excessive current in the frequency converter and damage the power transistor of the frequency converter.
Inverter braking and parking
Braking parking, also known as slope parking. Braking and parking can be divided into DC braking, power braking, feedback braking, hybrid braking, and mechanical braking.
The choice of parking method for the frequency converter depends on the required parking time on site. Usually, when the required parking time is less than the free parking time, braking and deceleration parking should be selected.
Direct current braking (i.e. supplying a certain amount of direct current to the power supply); Power braking (using resistors to dissipate energy); Hybrid braking (DC braking+power braking); Feedback braking (injecting the generated current into the power grid); Brake mechanical braking.
Parking is divided into inclined wave parking and free parking (fast parking is also inclined wave parking, but the slope is steeper).
Braking also includes mechanical braking (such as holding brakes), energy consumption braking (braking resistors, reverse braking, DC braking, etc.), feedback braking, etc. The need for braking is related to the operation status of the motor. When the required parking time is less than the free parking time during oblique wave parking, braking is required; Sometimes braking is also required when the motor is running normally, such as when the hook is lowered.
The working mode of resistance energy consumption braking
The method used for resistance energy consumption braking consists of two parts: the braking unit and the braking resistor, which consume electrical energy in high-power resistors through built-in or external braking resistors to achieve four quadrant operation of the motor. Although this method is simple, it has the following serious drawbacks.
(1) Simple energy consumption braking sometimes fails to timely suppress the pump voltage generated by rapid braking, limiting the improvement of braking performance (large braking torque, wide speed range, good dynamic performance)
(2) Wasting energy reduces the efficiency of the system
(3) The resistor heats up severely, affecting the normal operation of other parts of the system
Supporting braking method: The electric motor drives large inertia loads (such as centrifuges, gantry planers, tunnel cars, and large and small vehicles) and requires rapid deceleration or stopping; Electric motors drive potential energy loads (such as elevators, cranes, mine hoists, etc.); Electric motors are often in a dragged state (such as centrifuge auxiliary machines, paper machine guide roller motors, chemical fiber machinery stretching machines, etc.). The common characteristics of these types of loads require electric motors to not only operate in an electric state (first and third quadrants), but also in a power generating and braking state (second and fourth quadrants)
In the drive system composed of the power grid, frequency converter, motor, and load, energy can be transmitted bidirectionally. When the motor is in the electric motor working mode, electrical energy is transmitted from the grid to the motor through the frequency converter, converted into mechanical energy to drive the load, and the load therefore has kinetic or potential energy; When the load releases this energy in order to change the motion state, the motor is driven by the load and enters the generator working mode, converting mechanical energy into electrical energy and feeding it back to the front-end frequency converter. These feedback energies are called regenerative braking energies, which can be fed back to the grid through a frequency converter or consumed in the braking resistors on the DC bus of the frequency converter (energy consumption braking).
Occasions where braking energy is generated
1. Rapid deceleration process of large inertia load
2. The process of lowering heavy objects in lifting equipment
3. The process of lowering the donkey head of the beam pumping unit