5.3.4 Brake Option
Drives equipped with the dynamic brake option can
connect to an external brake resistor using the brake IGBT
and terminals 81(R-) and 82(R+).
The function of the brake IGBT (see
) is to
limit the voltage in the DC link, whenever the maximum
voltage limit is exceeded. To limit the voltage, it switches
the externally mounted resistor across the DC bus to
remove excess DC voltage from the bus capacitors.
Typically, excess DC bus voltage is a result of an
overhauling load causing regenerative energy to be
returned to the DC bus. This excess occurs, for example,
when the load drives the motor causing the voltage to
return to the DC bus circuit.
External placement of the brake resistor offers multiple
advantages:
•
Selecting the resistor based on application need.
•
Dissipating the energy outside of the control
panel.
•
Protecting the drive from overheating when the
brake resistor is overloaded.
The brake IGBT gate signal originates on the control card
and is delivered to the brake IGBT via the power card and
gate drive card. The power and control cards also monitor
the brake IGBT and brake resistor connection for short
circuits and overloads.
In parallel drive systems, the brake IGBT gate signal
originates on the control card. The signal passes through
the MDCIC, which delivers it to the power card and gate
drive card in each module. The power card and control
card also monitor the brake IGBT and brake resistor
connection for short circuits and overloads.
Internal Drive Operation
Service Guide
MG94A502
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