Hey, guys

What's the role of a brake resistor in the variable frequency drive system, and how to choose one for a 5HP drive?

The main role of the variable frequency drive braking resistor is: when the VFD drive in stop status, the electric motor is still running due to the motor inertia, it makes the motor become a generator, and such high-voltage can damage the inverter module, the brake resistor is installed can in order to prevent this high pressure.

During the fast stop process of the electric motor, it will produce large amounts of renewable energy due to the effect of the motor inertia, it will affect the intermediate DC section of the inverter directly. If this part of electricity can't be consumed, it will result in failure or damage to the variable frequency ac drive. Braking resistor is used to consume those electrical energy.

Every AC drive has a brake unit (small power is braking resistor, high power is high-power transistor GTR and drive circuit), small power is built-in, high-power normally is external connecting.

You can refer to the variable frequency ac drive user manual to configure the brake resistor.

The braking resistor in variable frequency inverter is used to consume the generate renewable energy in the regenerative braking, these renewable energy flow from the freewheeling diode feedback to the DC circuit and can not be feed back to the power grid, it will charge accumulation on the filter capacitor in a short period of time, make DC pressure increase and damage commutation devices. It is mainly used to release current and controlled by the power tube. Select the size according to the manual configuration on the line.

Brake resistor is used to consume the DC bus voltage to achieve variable frequency motor braking action

When the inverter drives motor or other inductive load during stop time, generally adopts dynamic braking, means consume the kinetic energy and the magnetic energy of the motor in the coil inside through a level of energy consumption components, in order to achieve fast stop function. When the power supply is off, the inverter circuit of the variable frequency AC drive reverses connection, and conducting these surplus energy feed back to the inverter DC bus, the DC bus voltage will be increased, and when it goes up to a certain value, the braking resistor will be put into operation, so this part of the electrical energy will be consumed by heating mode, and maintaining the voltage on the DC bus to a normal value.

You need to connect 3 pins on the back of the unit to power it up. It puts out about 12.49V out of the box, uneoadld. You throw a resistor between the voltage adjust pin and + to pull the voltage up, and you can put a resistor between another pin to slow the fan down. It's fairly well documented, just search DPS-600PB or HP ESP135. They're great supplies that can be found for $10-20. The light flashing in this video WAS the generator surging? due to a major air leak.