Inverter braking unit and braking resistor selection - Solutions - Huaqiang Electronic Network

RF cable can be customized for other specifications

Single chip microcomputer STM32L151CCU6

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22

Photocoupler

1. For inverters with different voltage levels and capacities, especially those with built-in braking units, the total resistance of the braking resistor must not be less than the allowable value specified by the braking unit.

2. Based on the typical range of commonly used inverters, it is recommended to choose one or two types of braking resistors and power ratings that match the system requirements.

3. When determining the braking power, consider the system's moment of inertia, mechanical load capacity, and the required stopping time. The braking power should be calculated based on the maximum instantaneous power of the braking unit.

3.1 System Inertia: If the system is not under load, you can estimate the inertia of each stage using software like SolidWorks. Since the mechanical system is designed in-house, the total inertia on the motor shaft is known after the design phase. The formula for calculating the total inertia on the motor shaft is: Motor rotor inertia (from the motor manual) + ((Load inertia / i²) + Transmission inertia) / i₁.

4. Braking power can be calculated as K multiplied by the energy consumption. By using series or parallel connections, both the resistance and power dissipation requirements can be satisfied. For example, for a 380V, 22kW inverter requiring a brake resistor of 27Ω, two 56Ω resistors connected in parallel will result in approximately 28Ω, which can meet the requirement of handling an instantaneous power of up to 26kW.

Additionally, when selecting braking components, it's important to ensure that they are compatible with the overall system design and operational conditions. This includes considering environmental factors such as temperature, humidity, and vibration, which may affect performance and longevity. Always refer to the manufacturer's specifications and guidelines to ensure safe and efficient operation.