For frequency converters equipped with the dynamic brake option, two brake IGBTs along with terminals 81(R-) and 82(R+) are included in each inverter module

for connecting an external brake resistor(s).

The function of the brake IGBT (see Illustration Brake Option) is to limit the voltage in the intermediate circuit, whenever the maximum voltage limit is exceeded.

It does this by switching the externally mounted resistor across the DC bus to remove excess DC voltage present on the bus capacitors. Excess DC bus voltage is

generally a result of an overhauling load causing regenerative energy to be returned to the DC bus. This occurs, for example, when the load drives the motor

causing the voltage to return to the DC bus circuit.

Placing the brake resistor externally has the advantages of selecting the resistor based on application need, dissipating the energy outside of the Keypad, and

protecting the frequency converter from overheating if the brake resistor is overloaded.

The Brake IGBT gate signal originates on the control card and is delivered to the brake IGBTs via the MDCIC to each inverter module power card and gate drive

card. Additionally, the power and control cards monitor the brake IGBT and brake resistor connection for short circuits and overloads.

High Power Service Manual for Unit Sizes 6x

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