FAQ

How to dimension the braking units and resistors for Delta frequency inverters
How to dimension the braking units and resistors for Delta frequency inverters

Introduction

In many applications, the braking resistor is necessary, as it helps to stop faster and protect the frequency inverter against overvoltages on the DC link. Some inverters already come with the built-in braking unit and others require one or more braking units.

Identifying the braking resistor and unit.

The simplest way to check the braking unit and resistor model is to go to the braking resistor table found in the user manual. For example, the frequency inverter of the C2000 series was considered.

 

Follow the steps below:

  1. Identify the voltage and power of the VFD. See the chapter “1-2 Model Name”Or the C2000 series catalog.

 

 

  1. Once the voltage and power of the VFD has been identified, see the chapter “7-1 All Brake Resistors and Brake Units Used in AC Motor Drives” in the C2000 user manual. In this chapter it is possible to identify the braking units and resistors according to the voltage and power of the inverter.

 

    1. Example: VFD007C23A (0.7kW / 230Vac)

 

In example “a”, the VFD will need 1 x 80W / 200Ohms resistor that will be connected directly to the frequency inverter without the need for a braking unit.

 

    1. Example: VFD300C23A (30kW / 230Vac)

For example “b”, the VFD will need 2 x braking units (VFDB2015) and 4 x 4000W / 5.1Ohms braking resistors. 2 x resistors in series will be used per braking unit.

 

For more information, see the manual for the braking units of the respective frequency inverter.

 

Grades:

  • It is extremely important that the resistor has a thermal relay (OL) to indicate overtemperature.
  • Note that this resistor is for 10% ED. Check if your application needs a higher percentage of DE.

  • Consider environmental safety factors when installing the braking resistors. If you use the minimum resistance value, consult your local dealer to recalculate the resistor values.
  • When using more than two braking units, the equivalent resistor value of the braking unit in parallel cannot be less than the value in the minimum ohmic resistance column “Minimum Resistor Value (Ω) ”. Read the wiring information in the braking unit user manual completely before operation.
  • The table above is for normal use; if the unit is applied for frequent braking, it is suggested to increase the power in Watts by 2 to 3 times.

Conclusion

These steps apply to other Delta frequency inverter families. Search the user manual and the brake unit manual of the respective frequency inverter to find the information mentioned.