JOHNSON CONTROLS
192
FORM 201.23-NM2
ISSUE DATE: 09/25/2020
SECTION 6 - TECHNICAL DATA
Laminated Bus Structure
The Laminated Bus Structure is a group of copper
plates sandwiched together that connects the SCR/Di-
ode Modules, Bus Filter Capacitors, and IGBT’s. The
purpose of the Laminated Bus Structure is to reduce
the inductance that would be present in wiring or bus
bars often used to connect high voltage components
in VSD’s. Removing inductance in the circuit reduces
the voltage spike that occurs when the IGBT’s turn
off. These voltage spikes can potentially damage the
IGBT’s.
LD10614
LAMINATED BUS
STRUCTURE
VSD Logic Board
The VSD Logic Board controls VSD functions/op-
erations and communicates through a serial commu-
nications line with the Chiller Control Board. Safety
and shutdown information stored in the RTC (Battery
backed RAM) is reported back to the Chiller Control
Board via the communications link. The VSD Logic
Board converts the speed and run commands from the
Chiller Control Board into the necessary voltage and
frequency commands to operate the inverter section.
The VSD Logic Board also controls the converter sec-
tion of the VSD (AC to DC conversion) by controlling
the pre-charge function.
The VSD Logic Board contains a second microproces-
sor for motor control, which generates the PWM sig-
nals that control the IGBT’s in the inverter section of
the VSD.
LD13120
RTC
FIGURE 47 - NEW BOARD P/N 031-02507-000
The VSD Logic Board contains an FPGA (Field Pro-
grammable Gate Array) which handles the hardware
safeties and can shut down the VSD much faster than
the software safeties, since they are not dependent upon
running program loops in software. The VSD handles
all VSD related safeties including high motor current,
overload, DC Bus voltage faults, etc.
FIGURE 48 - OBSOLETE BOARD P/N 031-02477-000
LD10615
RTC
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