Inverter braking unit and braking resistors - News - Global IC Trade Starts Here.

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1. Braking torque = ((motor moment of inertia + motor load measured to the motor measured moment of inertia) * (pre-brake speed - brake speed)) / 375 * deceleration time - load torque under normal circumstances, When the motor is braked, there is a certain loss inside the motor, which is about 18%-22% of the rated torque. Therefore, if the calculated result is less than this range, there is no need to connect the brake device;
2. The resistance of the braking resistor = the square of the operating voltage value of the braking element / (0.1047 * (brake torque - 20% motor rated torque) * motor speed before braking)
During the operation of the brake unit, the voltage rise and fall of the DC bus depends on the constant RC, R is the resistance of the brake resistor, and C is the capacity of the internal electrolytic capacitor of the inverter. Here, the braking unit operating voltage value is generally 700V.
3. Selection of braking unit When the braking unit is selected, the maximum operating current of the braking unit is the only basis for selection. The calculation formula is as follows:
Brake current instantaneous value = brake unit DC bus voltage value / braking resistance value
4. The nominal power of the braking resistor Because the braking resistor is a short-time working mode, according to the characteristics and technical specifications of the resistor, we know that the nominal power of the resistor will be less than the power consumption during power-on, which can be obtained by the following formula: Braking resistor nominal power = braking resistor derating factor X average power consumption during braking X braking usage %
It should be noted that: The advantage of energy braking (resistive braking) is that the structure is simple, and the disadvantage is that the operating efficiency is reduced, especially when frequent braking, a large amount of energy will be consumed, and the capacity of the braking resistor will increase.