Braking resistor is a kind of corrugated resistor, which is mainly used in the mechanical system where the inverter controls the motor to stop quickly, to help the motor convert the regenerative electric energy generated by the rapid stop into heat energy.

member

Ceramic tube

It is the skeleton of alloy resistance wire and has the function of radiator at the same time.

Alloy resistance

The flat ribbon has a wave shape, wound on the surface of the ceramic tube, and is responsible for converting the regenerative electric energy of the motor into heat energy.

coating

Coated on the surface of alloy resistance wire, it has high temperature resistance and its function is flame retardant.

principle

1. Principle of the braking unit: The braking unit is composed of a high-power transistor GTR and its drive circuit. Its function is to add an external braking component to speed up the consumption of regenerative power when the capacitor in the discharge current link cannot be stored within the specified voltage range or the internal braking resistor is too late to be consumed and the DC part is "overvoltage". .

2. Principle of braking resistor: The motor will be in a regenerative braking state during the process of decreasing the working frequency. The kinetic energy of the drag system must be fed back to the DC circuit, so that the DC voltage UD will continue to rise, and it may even reach a dangerous point. Therefore, the energy regenerated to the DC circuit must be consumed to keep the UD within the allowable range. The braking resistor is used to consume this part of energy.

3. Braking unit + resistance: The braking unit is composed of a high-power transistor GTR and its drive circuit. Its function is to provide a path for the discharge current IB to flow through the braking resistor.

The following is the action process of the braking unit:

a. When the motor decelerates under the action of external force, the motor runs in a generating state to generate regenerative energy. The three-phase AC electromotive force generated by the inverter is rectified by a three-phase full-control bridge composed of six freewheeling diodes in the inverter part of the inverter, which continuously increases the DC bus voltage in the inverter.

b. When the DC voltage reaches a certain voltage (the turn-on voltage of the braking unit), the power switch of the braking unit is turned on and the current flows through the braking resistor.

c. The braking resistor releases heat and absorbs regenerative energy, the motor speed drops, and the inverter DC bus voltage drops.

d. When the DC bus voltage drops to a certain voltage (brake unit stop voltage), the power tube of the brake unit is turned off. At this time, no braking current flows through the resistor, and the braking resistor is naturally dissipating heat, reducing its own temperature.

e. When the voltage of the DC bus rises again to cause the braking unit to act, the braking unit will repeat the above process to balance the bus voltage and make the system operate normally.

Because the working condition of the brake unit is short-time work, that is, the power-on time is very short each time, and the temperature rise is far from stable during the power-on time; and the intermittent time after each power-on is longer. In the intermittent time, its temperature is enough to drop to the same as the ambient temperature, so the rated power of the braking resistor will be greatly reduced, and the price will also decrease; in addition, because there is only one IGBT, the braking time is ms level, and the power tube is turned on and The transient performance index of the turn-off is low, and the turn-off time is even required to be as short as possible to reduce the turn-off pulse voltage and protect the power tube; the control mechanism is relatively simple and easy to implement. Because of the above advantages, it is widely used in cranes and other potential energy loads and occasions that require rapid braking but are short-time work systems.