4.22 Inverter
The function of the Inverter is to take the DC bus voltage as an input and generate the AC output voltage to the
compressor motor at the required fundamental frequency to generate the requested shaft speed. Voltage to the
motor is also controlled to provide the appropriate motor torque.
The Backplane sends +24VDC and gating signals to the Inverter from the BMCC. In return, the Inverter sends current,
temperature, error, and DC bus voltage information to the BMCC via the Backplane. Motor currents and voltages
displayed in the SMT cannot be directly compared or correlated to incoming 3-phase AC values.
In the event of a 3-phase voltage power loss while the compressor is running, the Inverter switches to Generator
Mode, acting as a rectifier to maintain the DC bus voltage until the shaft comes to a complete stop and de-levitates.
4.22.1 Inverter Connections
Figure 4-189 Inverter Connections
4.22.2 Inverter Verification
This procedure only verifies the Inverter high-power diodes. The Inverter Control Board cannot be verified in the
field unless an inverter tester is used. A faulty Inverter may also appear as an “Inverter Error” fault.
1. Isolate the compressor power as described in Section 1.8 Electrical Isolation on page 22.
2. Remove the Soft Start Module. Refer to Section 4.14.3 Soft Start Removal and Installation on page 117.
3. Remove the DC Capacitor Bus Bar Assembly. Refer to Section 4.21.3 DC Capacitor Bus Bar Assembly
Removal and Installation on page 168.
4. Remove the Copper Tubes and fasteners connecting the motor bus bars to the Inverter Module. Refer
to Figure 4-195 Inverter Copper Tube Removal on page 180.
5. Disconnect the Inverter ribbon cable from the Inverter Module.
• • • CAUTION • • •
A faulty Inverter module could be the result of a faulty Stator. If an Inverter module is found to be faulty, the Stator must be verified as
well.
6. Using a multimeter set for diode measurements, place the red (+) multimeter lead on the phase 1 AC
terminal and the black (-) multimeter lead on the DC+ terminal. The measured value should be 0.275V –
0.4V. Refer to Figure 4-190 Inverter Diode Measurements (Skiip 613 Shown) on page 177 for this and
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Summary of Contents for Turbocor TT Series
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