AMETEK Ls Series - Manual (Page 97)

User Manual Lx / Ls Series
93
5. Principle of Operation
5.1 Overall Description
Three-phase input power is routed from the back of the cabinet to a fuse holder terminal block
located in the bottom front of the unit. AC power is converted to a 300 VDC bus using a
switching buck converter. The DC bus is used to power all three DC/AC invertors (amplifiers),
one for each phase. The AC input converter also generates the required DC bias supply
voltages to power the auxiliary circuits of the power source such as the programmable controller
and keyboard display.
The output of each amplifier is fed through an output transformer which steps the output voltage
to the required 150 V AC RMS or 300 V AC RMS output range. The output transformers provide
the required isolation between input and output and also block any DC at the output of the power
source.
The CPU controller / oscillator assembly generates the reference waveforms and provides
frequency, amplitude, and current limit control. A current and voltage sense board is located at
the top right of the unit above the transformers and is used to sense all output current and
voltage for both control and measurement purposes. The current sensor board, in conjunction
with the CPU controller, also supports the programmable RMS current limit function.
To obtain higher power levels, two 4500Lx (4500 VA) power sources are paralleled together to
form a 9000V VA three-phase AC source. This is accomplished through the system interface,
which routes the required analog and digital signals from the 4500Lx master (unit with controller
front panel) to the 4500Lx auxiliary.
5.2 Controller Assembly
The Controller Assembly is located on the front panel the Lx/Ls master unit. The controller
assembly consists of a single printed circuit board that plugs into the backplane motherboard.
The controller contains the main oscillator, which generates the sine wave signal setting the
frequency, amplitude and current limit level. It also senses the output voltage to provide closed
loop control of the output. The controller also handles all user interface and remote control
related tasks. The function of each of the two boards that make up the controller module is
described in the following paragraphs.
5.2.1 Programmable Controller
This board assembly, A7, consists of the components for the CPU (DSP), generating all three
Phase waveform signals to the power amplifier and all of the program, waveform and data
memory. In addition, this board contains the circuits for all measurements. The clock and lock
circuit required to support the clock and lock mode of operation of multiple Lx/Ls units is also on
this board assembly.
5.2.2 Keyboard / Display Board
The keyboard/display assembly is assembly A9 and is mounted to the front panel. If the Lx/Ls
system is used over one of the remote control interfaces, the keyboard functions can be locked
out by asserting the REMOTE state. See the Lx/Ls Series Programming Manual (P/N 9003-961)
for details.