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Selection of brake resistor in construction elevator
Feb 07, 2018

Selection of brake resistor in construction elevator

As the frequency conversion system used in the construction elevator hoisting and lowering, the design emphasis of the braking resistor lies in the system reliability when the motor is in the feedback braking state, because the failure of such a system often occurs when the cage descends, such as overvoltage , Speeding, rolling the car and so on. Frequency conversion system in the heavy weight down process, the motor is in power generation. The regenerative power is returned to the DC bus of the inverter. In this case, the DC link is usually used to connect the braking unit and the braking resistor to other energy-consuming devices.

Figure can be used to indicate the various parameters of the elevator frequency system in the process of decline in the situation.

The steady-state power consumed by the resistor at a constant drop

Pe = ωmMeδ (2)

Peak power consumption during deceleration

Pm = Pe + δJ (ωm-ωd) / Ta (3)

Where ωm --- decline speed before deceleration

Ωd --- decline speed after deceleration

Me --- load torque

Δ --- drive system reverse efficiency

J --- transmission system of inertia

Ta --- deceleration time

To determine the exact value of these parameters in the early stages of system design is a certain degree of difficulty. Before the product is not completed, it is impossible to accurately measure and calculate the transmission inertia of each component. In actual use, the deceleration characteristic of the system may change according to the needs of the site. So in most cases, the value of experience generally according to motor power between 40% ~ 70%. The braking resistor R calculated by the following range selected

Rmin ≦ R ≦ Vc2 / 0.8P (4)

Rmin ≦ Vc / Ic (5)

Where Vc --- braking unit operating voltage

Ic --- brake unit maximum allowable current

P --- motor rated power