The supplier of the frequency converter braking unit reminds you:
1. The significance of power generation braking during power frequency operation is:
1) For example, when lifting an asynchronous motor, it is dragged to generate electricity at noon during the process of lifting and falling. At this time, the asynchronous motor is in a generating state, and the generated current is the braking current. At this time, the gravitational potential energy of the heavy object is converted into electrical energy and fed back to the power grid;
2) That is to say, how to lift heavy objects when the asynchronous motor rotates forward, and how to lower heavy objects when rotating backward, without worrying about heavy objects falling off when the motor rotates backward;
3) Power generation braking, without the need for any equipment, is a normal operating state of asynchronous motors, that is, a four quadrant operating state. The "electric" or "power generation" is determined by the load carried, automatically switching, stable, safe, and reliable;
2. The significance of energy consumption braking during power frequency operation is:
1) A method used when the motor needs to stop quickly after stopping;
2) After stopping and cutting off the power, immediately apply direct current to the motor winding to generate a constant magnetic field. At this time, the rotor, which is in inertial high-speed motion, will cut the magnetic field lines and generate electricity. The rotor current generated by the rotor's power generation is the braking current, which converts the kinetic energy of the rotor and load's inertial motion into electrical energy, which is then consumed by the resistance of the rotor winding, causing the rotor to heat up;
3. During variable frequency operation:
1) Soft parking belongs to asynchronous motor power generation braking. Asynchronous motors convert the inertial kinetic energy of the rotor and load into electrical energy, which is rectified by an inverter circuit and enters the DC section, causing the DC section voltage to rise because this electrical energy cannot be fed back to the grid;
2) For frequency converters, asynchronous motor power generation and braking can cause overvoltage protection in the DC section, which is a bad thing. The solution is to use braking resistors to burn off this electrical energy;
3) There are also feedback units that can reverse the generated braking energy into AC power and feed it back to the grid, but the effect is not as smooth and effective as when asynchronous motors are directly connected to the grid;
4. During variable frequency operation:
1) During variable frequency operation, if there is a free stop, it means that the inverter stops outputting AC power and supplies DC power to the asynchronous motor;
2) At this time, the winding of the asynchronous motor generates a DC constant magnetic field under the action of DC current, the rotor cuts the magnetic line of force to generate electricity, and consumes the braking energy on the rotor winding, which is the same as the energy consumption braking of the motor during power frequency operation;
3) After the frequency converter stops freely, it no longer outputs AC power but outputs DC power, which is the characteristic of DC energy consumption braking;