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M-AP-001-EN Rev. N
The Bearing PWM Amplier supplies current to the radial and axial magnetic bearing
actuators.
The PWM Amplier consists of high-voltage switches that are turned on and o at a high
frequency, as commanded by the PWM signal from the BMCC.
The Serial Driver module performs serial-to-parallel conversion on the stepper motor drive
signals from the BMCC. The module also contains four normally open relays under BMCC
control. Two of the relays drive the motor-cooling solenoids, and the other two are used
to indicate compressor fault status and running status. The status relays can be wired to
external control circuits.
3.4.10 Bearing PWM
Amplier
3.4.11 Serial Driver
The Backplane physically interconnects the on-board plug-in modules with the power
electronics, IGV stepper motor, motor-cooling solenoids, rotor position sensors, and
pressure/temperature sensors. The Backplane also features on-board, low-voltage DC-
DC converters for generating +15V, -15V, +5V, and +17V from an input of +24VDC. The
Backplane receives its +24VDC power input from the High-Voltage (HV) DC-DC Converter
mounted on the topside of the compressor.
The Backplane is also equipped with status-indicating LEDs. All LEDs are yellow except for
the alarm LED, which is green/red. Table 3-1 Backplane LEDs describes the LEDs functions.
3.4.12 Backplane
Table 3-1 - Backplane LEDs
LED Function
+5V, +15V, +17HV,
+24V
LEDs are lighted when DC power is available.
Cool -H, Cool -L LEDs are lighted when their respective coil is energized.
Run LED is lighted when the shaft is spinning.
Alarm LED is green when in normal status, red when in alarm status.
D13, D14, D15, D16 LEDs indicate IGV status and ash when IGV is moving.
Functional Description
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