Usage rate

The use rate of the braking resistor specifies the use efficiency of the braking resistor to avoid overheating and damage to the braking resistor, which will affect the braking effect of the braking unit. The lower the usage rate of the braking resistor is set, the smaller the heating degree of the resistor, the less energy is consumed on the resistor, and the worse the braking effect. At the same time, the capacity of the braking unit has not been fully utilized. Theoretically, when the braking resistor utilization rate is 100%, the capacity of the braking unit is fully utilized and the braking effect is the most obvious. However, this requires a larger braking resistor power, and the user should consider it comprehensively. Under the premise that the resistance and power of the braking resistor have been determined, for a slower deceleration large inertia load, a lower resistance usage rate will achieve better results. For loads that need to be stopped quickly, a larger braking resistor utilization rate should be selected.

Derating options

The braking resistor power calculated according to the above method is sufficient, and it can be further derated according to the nature of the load.

Non-repetitive braking

The so-called non-repetitive braking means that the drive system has only one deceleration and braking process in a relatively long period of time. Therefore, the braking resistor only consumes energy once during this period, and the power of the braking resistor can be further improved. Decrease, the magnitude of the decrease depends on the impact resistance of the braking resistor and the action time of a single deceleration braking. Regardless of the impact resistance of the braking resistor, in a non-repetitive braking system; when the braking time is less than 10S, the power of the braking resistor can be derated below 20%.

Repeat braking

Some machinery requires repeated braking, such as hoisting machinery and gantry planers. In the case of repeated braking and short braking time, the selection of braking resistor power P and the braking duty cycle (each braking The ratio tb/tc) between the time tb and the time interval tc between two brakings has an approximately linear relationship. The smaller the braking duty cycle, the greater the derating of the braking resistor power (P selection/P rating is smaller).

(Note: When the braking time is long and braking is repeated, the selection of braking resistor power should consider leaving a certain margin).