Braking Units; Internal Braking Unit - gefran SIEIDrive AVy Series Quick Start Up Manual

5.8. BRAKING UNITS

In oversynchronous or regenerative operation, the frequency-controlled three-phase motor feeds energy
back to the DC link circuit via the Drive. This leads to an increase in the intermediate circuit voltage.
Braking units (BU) are therefore used in order to prevent the DC voltage rising to an impermissible value.
When used, these activate a braking resistor that is connected in parallel to the capacitors of the intermediate
circuit. The feedback energy is converted to heat via the braking resistor (R
deceleration times and restricted four-quadrant operation.
_
R
BR
BU
Drive sizes 1007 up to 4185 have, as standard configuration, an internal braking unit.
Drive sizes 4220 up to 5550 can have an optional internal braking unit (see section 3.1.2 "Inverter type
designation") factory mounted. All the standard AVy... drive can be equipped with an external braking unit
(BU-32...) connected to the terminals C and D.
N !
When the internal braking unit is present, or when circuit terminals C and D are con-
OTE
nected to external devices, the AC Input must be protected with superfast semiconductor
fuses! Observe the mounting instruction concerned.
For braking resistor connection (terminals BR1 and C) a twisted cable has to be used. In
case the braking resistor is supplied with thermal protection (klixon), it may be connected
to the "External fault" drive input.
W !
The braking resistors can be subject to unforeseen overloads due to possible failures.
ARNING
The resistors have to be protected using thermal protection devices.
Such devices do not have to interrupt the circuit where the resistor is inserted but their
auxiliary contact must interrupt the power supply of the drive power section.
In case the resistor foresees the precence of a protection contact, such contact has to be
used together with the one belonging to the thermal protection device.

5.8.1. Internal braking unit

The Internal Braking Unit is included as standard (up to size 4185). The braking resistor is optional and has
always to be mounted externally. For parameter setting refer to the optional "AVy-Function description and
parameters" instruction manual (available on CD), section 2.15.9 Braking unit. The figure below shows
the configuration for internal brake unit operation.
Figure 5.8.1.1: Connection with internal Braking Unit and external braking resistor
Figure 5.8.1: Operation with Braking Unit (Principle)
U
ZK
Braking
Unit
F1
3Ph~
—————— Wiring procedure ——————
), thus providing very short
BR
M
3
AC Motor
Braking
resistor
E
81 Ch.5