163
JOHNSON CONTROLS
FORM 201.21-NM1 (1223)
6
CHILLER ELECTRONIC COMPONENTS (CON'T)
1L LINE INDUCTOR
LD10612
1L LINE INDUCTOR
The 5% impedance 1L Line Inductor has multiple
functions. 1L forms a low pass LC lter that lters the
pulsating DC from the AC to DC converter, to smooth
DC voltage. The inductance eliminates notches on the
incoming AC line. The inductance also helps protect the
SCR’s from high voltage incoming line transients, which
could damage them. 1L slows down the rate of rise of
current if an internal short circuit occurs, reducing the
potential damage caused by the short. 1L also reduces
the input current total harmonic distortion.
DC TO AC INVERTER
The DC to AC Inverter section converts the rectied
and ltered DC back to AC at the equivalent magnitude
and frequency to run a compressor at a specic speed.
Although a common DC Bus links the compressor drive
outputs, each compressor has it’s own inverter output
module. Each inverter output module consists of 6
IGBT’s (3 modules) and an IGBT Gate Driver Board,
which converts DC to a 3 - phase AC output. The IGBT’s
are mounted to the liquid cooled heatsink designed to
take the heat away from the devices and remove it in
the condenser. The IGBT Gate Driver Board provides
gating pulses to turn the IGBT’s on and o.
LD10613
IGBT'S IGBT'S
LAMINATED BUS STRUCTURE
The Laminated Bus Structure is a group of copper plates
sandwiched together that connects the SCR/Diode Mod-
ules, 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 o. These voltage spikes
can potentially damage the IGBT’s.
LD10614
LAMINATED BUS
STRUCTURE
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