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M-SV-001-EN Rev. G
4.25 High Voltage DC-DC Converter
There are two (2) variants of the DC-DC Converter mentioned in this manual. There is a potted style
which has been in production for years and there is the open frame DC-DC converter that was
released to production as replacement of the potted style in April 2019. The removal and installation
of the two (2) variants are very similar. The open frame style utilizes six (6) mounting fasteners while
the potted style uses eight (8). The open-frame style utilizes three (3) connectors whereas the potted
style uses four (4). The open frame design no longer uses the 15VAC trigger signal from the Soft Start,
thus eliminating the need for J7.
The open frame DC-DC Converter is fully backwards compatible, and it handles all of the voltage
applications. The potted DC-DC Converter is specific to a given voltage; because of that, potted DC-DC
Converters cannot be swapped to a compressor of a different voltage.
4.25.1 DC-DC Converter Function
The DC-DC Converter provides the Backplane with +24VDC (with respect to 0V) and HV+
(+250VDC with respect to HV-) for the Bearing PWM Amplifier.
DC bus voltage (460-900VDC) is supplied to the DC-DC converter through the Soft Start Board F1 fuse.
The Soft Start Board also powers the potted-style DC-DC Converter with 15VAC when the DC bus has
reached minimum level.
Refer to "Figure 4-258 Potted DC-DC" on page 204 and "Figure 4-259 Open Frame DC-DC" on page
204 for the DC-DC Converter input-output (I/O) connections:
Inputs:
• J1 Bus Input
• J4 15VAC (potted version only)
Outputs:
• J2 250VDC
• J3 24VDC (potted) J4 24VDC (open frame)
4.25.2 DC-DC Converter Verification
4.25.2.1 Input Voltage Verification
1. Isolate the compressor power as described in Section "1.8 Electrical Isolation" on page 19.
2. Install the DC bus test harness. Refer to "1.10.1 General Verification and Installation of the DC
3. Turn on the mains power to the compressor.
4. Using the DC bus test harness, verify the expected voltages are present. Refer to "Table 4-19
Expected AC Voltage Range" on page 98.
4.25.2.2 Output Voltage Verification
1. Remove the Service Side Cover. Refer to "4.2.3.1 Service Side Cover Removal and Installation"
2. With mains power on, using a multimeter set for DC voltage measurements, place the
multimeter leads in the HV+ and HV- test points on the Backplane. Refer to "Figure 4-266
Backplane Test Points" on page 209 for this and the following step. The result should be 220 –
280 VDC.
3. Place the multimeter leads in the +24 and 0V test points on the Backplane. The result should
be 22 – 26 VDC.
Summary of Contents for Turbocor TTS Series
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