￭
Brake chopper
A brake chopper can be used to handle the energy generated by a decelerating
motor. When the DC voltage rises high enough, the chopper connects the DC circuit
to an external brake resistor. The chopper operates on the pulse width modulation
principle.
The brake chopper (43.6) can be enabled with the overvoltage controller (30.30)
still active. In such case, make sure the overvoltage controller limits are set high
enough not to limit before the full braking power is reached. This function in certain
applications avoids unnecessary overvoltage trip and implements a simpler control
logic if the resistor cannot absorb enough energy or when the resistor breaks
during breaking.
Some ACS880 drives have an internal brake chopper as standard, some have a
brake chopper available as an internal or external option. See the appropriate
hardware manual or sales catalog.
The internal brake choppers of ACS880 drives start conducting when the DC link
voltage reaches 1.156 ×
U
DCmax
. 100% pulse width is reached at approximately 1.2
×
U
DCmax
, depending on supply voltage range – see table under Voltage control
and trip limits above. (
U
DCmax
is the DC voltage corresponding to the maximum
of the AC supply voltage range.) For information on external brake choppers, refer
to their documentation.
Note: For runtime braking, overvoltage control (parameter 30.30) needs to be
disabled for the chopper to operate.
Settings and diagnostics
Parameters: 1.11 DC voltage (page 135) and 30.30 Overvoltage control (page 312).
Parameter group: 43 Brake chopper (page 359).
￭
DC voltage boost
This section describes the use of the DC voltage boost function for the drives
which has separate IGBT supply unit control.
The DC voltage boost require drive derating. See hardware manual of the drive for
derating factors.
Description of the DC voltage boost function
The regenerative and ultra low harmonic drives can boost their DC link voltage. In
other words, they can increase the operating voltage of the DC link from its default
value.
The user can take the DC voltage boost function in use by:
1. Adjusting the user-defined DC voltage reference value (94.22) and
106 Program features
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