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The supply unit connects to the AC supply network. The supply unit converts the AC voltage
into DC. The DC voltage is distributed through the DC bus to all inverter and brake units.
The inverter unit, consisting of one or more inverter modules, converts the DC back to AC
that rotates the motor. The brake unit, consisting of one or more brake chopper modules,
conveys energy to brake resistors whenever needed.
Brake module hardware
￭
General
A brake unit contains one or more 3-phase brake chopper modules connected in parallel,
together with the necessary auxiliary equipment such as control electronics, fusing and
cabling. All brake modules have coated circuit boards as standard.
The modules run on wheels, and can easily be removed from the cubicle for cable installation
or service.
The output connection is via a quick connector at the back of the module that couples when
the module is inserted into the cubicle. Each parallel-connected module is cabled separately
to the brake resistors.
The internal control electronics of the module must be powered from an external auxiliary
voltage. The cooling fan is automatically speed-controlled according to the loading of the
brake module. The fan is supplied from the DC input. A direct-on-line fan, supplied from an
external 3-phase source, is optionally available.
Internal du/dt filtering is included as standard.
Each parallel-connected brake module is controlled by a dedicated control unit. The control
unit is installed separately from the module. The control unit is connected to each brake
module by a fiber optic link. The control unit can be powered from a brake module, from an
external 24 V DC supply, or both for redundancy. Each control unit contains the basic I/Os
and slots for optional I/O modules. Other equipment is primarily installed on separate
mounting plates.
￭
DC connection and capacitor charging
The module must be equipped with external DC fuses.
A DC switch/disconnector can be installed if quick isolation of the module from the DC bus
is required.
A capacitor charging circuit must be fitted if:
•
the module is connected to the DC bus through a DC switch/disconnector, or
•
the module is directly connected to the DC bus and the supply unit of the system does
not have a charging capability.
The charging circuit design presented in this manual consists of a charging switch, resistors
and a charging controller. When the module is connected to an energized DC bus, the
charging switch is closed first. When the charging is finished, the main DC
switch/disconnector can be closed and the charging switch opened. The module will not
start if the charging switch is closed.
Common mode filtering is implemented by running the DC bus through ferrite cores at the
input of the module.
Operation principle and hardware description 17
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