Brake Options - Siemens COMBIMASTER Reference Manual

7.4 Brake Options

Pulse Resistor Braking Unit
(Only available for CS B Inverters)
The pulse resistor braking unit gives the
COMBIMASTER increased immunity to over
voltage trips, and can also be used to provide
up to 7kW (peak) of braking power for stopping
the system more quickly than would otherwise
be possible.
The braking unit fits in place of the standard
cover for the inverter unit. It houses the braking
control electronics, and a 7kW (peak) braking
resistor with heat sink. Full IP65 environmental
protection is maintained.
Technical Overview
The electronics operates completely
independently of the inverter electronics,
monitoring the DC link voltage. During braking,
the motor will regenerate, causing the DC link
voltage to rise. When a set threshold is
reached, the unit switches the resistor onto the
DC link, causing the regenerated energy to be
dissipated as heat in the resistor, and
preventing an over voltage trip.
50
COMBIMASTER & MICROMASTER Integrated
While the resistor is switched on, its
temperature will rise. When a threshold
temperature (Tmax) is reached, the unit will
limit the power in the resistor to approximately
5% of the peak power. (350W). If the
temperature continues to rise, the resistor will
be disabled completely, until the temperature
has reduced. The following diagrams show the
relationship between braking power, and
resistor temperature with time.
P1
P2
T1 T2
Tmax
T1 T2
Figures given below are for a 7kW (peak)
braking unit. T1 and T2 are variable,
depending on ambient temperature. However
typical figures are given.
P1 - 7kW
P2 - 350W
T1 - 5 Seconds typical
T2 - 100 Seconds typical
Protection
In the event of a braking unit fault, it is possible
for the resistor to become permanently
connected, and to overheat. The resistor
temperature is monitored by an internal circuit,
and if it becomes too hot , this is indicated by a
fault relay. This relay should be used to control
an external contactor, to remove power from
the COMBIMASTER. See the braking unit
installation instructions for more information.
Siemens plc. 1999
© | G85139-H1731-U300-D2
REFERENCE MANUAL