Figure 3-22 Braking Chopper Design - ABB ACS1000i User Manual

3.4.12.1. Control principle
If the DC-link voltage rises above a preset limit, the control system of the ACS1000i
automatically activates the braking chopper. A rise of the DC-link voltage can be caused by
a machine, feeding into the DC link or by an increase of the voltage in the rectifier of the
ACS1000i.
Figure 3–22 Braking chopper design
1) Semiconductor stack
3.4.12.2. Monitoring and protective functions
Current monitoring
Input currents of the braking chopper are monitored for overcurrent and imbalance in order
to detect any defective component in the circuit. The current can become imbalanced if one
of the IGCTs conducts a current permanently or if an IGCT fails to be switched on.
If a short-circuit or an imbalance is detected in the braking chopper, the drive is shut down.
Thermal protection
The braking chopper and the braking resistors are monitored for over-temperature by
the ACS1000i.
In addition, an external thermal protection device can be connected to a digital input. As
soon as the temperature of the braking resistors exceeds the response threshold of the
external thermal protection device, the operation of the braking chopper is disabled and an
alarm message is displayed on the control panel of the ACS1000i. Braking is then only
possible when the temperature falls below the threshold.
PRODUCT
ACS1000i
DOCUMENT KIND
User manual
POWER ELECTRONICS AND CABINET FEATURES
1
DOCUMENT ID.
3BHS206977 E01
REV. LANG. PAGE
J en 39/146