Danfoss Turbocor TT Series, Service Manual, Page: 141 / 294

4.18 Silicone-Controlled Rectifier
The AC input voltage is connected to the SCRs by the Mains Input bus bars. The SCRs are used to convert the AC
voltage into DC voltage. SCRs maintain the high voltage DC bus necessary to provide power to the Inverter to run
the compressor motor.
Using both the AC input voltage and the DC voltage output from the SCRs, the Soft Start Board generates the gate
signal and outputs pulses of 0-12VDC to the SCRs to control the in-rush current when power is initially applied to
the compressor. This is used while the DC capacitors are charging up.
The DC bus voltage output from the SCRs is approximately 1.35 times that of the AC input voltage (460-900VDC).
There are two (2) different styles used for the compressors. Refer to Figure 4-139 SCR Styles for the visual differences.
Figure 4-139 SCR Styles
4.18.1 SCR Connections
Refer to Figure 4-140 SCR Connections - TTS300/TGS230 and Figure 4-141 SCR Connections - TTS/TGS/TTH/TGH Rev.
F and Earlier (Except TTS300/TGS230) on page 142 to locate the following connections to the SCRs:
l
AC input to SCR
l
SCR Gate cables to Soft Start
l
SCR to DC bus
Figure 4-140 SCR Connections - TTS300/TGS230
M-SV-001-EN Rev. H-1/23/2023 Page 141 of 294