GE Industrial Solutions AF-650 GP General Purpose Drive - Manual (Page 23)

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Some of the GE Brake resistors contain a thermal switch. This switch is NC (normally closed) and can be used e.g. coasting stop reverse between terminal 12 and
27. The drive will then coast, if the thermal switch is opened.
The thermal switch must comply with PELV.
The brake is protected against short-circuiting of the brake resistor, and the brake transistor is monitored to ensure that short-circuiting of the transistor is detected.
A relay/digital output can be used for protecting the brake resistor against overloading in connection with a fault in the frequency converter.
In addition, the brake makes it possible to read out the momentary power and the mean power for the latest 120 seconds. The brake can also monitor the power
energizing and make sure it does not exceed a limit selected in par. B-12 Brake Power Limit (kW). In par. B-13 Braking Thermal Overload, select the function to
carry out when the power transmitted to the brake resistor exceeds the limit set in par. B-12 Brake Power Limit (kW).
NB!
Monitoring the brake power is not a safety function; a thermal switch is required for that purpose. The brake resistor circuit is not earth leakage protected.
Over voltage control (OVC) (exclusive brake resistor) can be selected as an alternative brake function in par. B-17 Over-voltage Control. This function is active for
all units. The function ensures that a trip can be avoided if the DC link voltage increases. This is done by increasing the output frequency to limit the voltage from
the DC link. It is a very useful function, e.g. if the decel time is too short since tripping of the frequency converter is avoided. In this situation the decel time is
extended.
AF-650 GP Brake Resistor Design Guide
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