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I moved to a new company that makes very big old-style controlled rectifiers. They asked me to make a new modified, and enhanced thyristor-controlled rectifier. The strangest problem I faced is that they use a high-side shunt resistor to measure the current of the rectifier. Besides that, the rectifier output could reach 450 VDC.

They had an old controller from which I reverse-engineered the voltage and current measurement circuit and I was shocked.

To measure the high-side shunt, they connected the GND of the circuit to the (I-) side of the shunt resistor which could reach 450VDC.

Is this a good or even an acceptable design?

Please check the schematic below:

enter image description here

I think the jumpers are there to choose between high-side or low-side shunt systems.JP7 & JP8 do not make any sense to me, they connect JP7 & JP8 & JP5 when using the high-side shunt.

My new design will have a programming connector and a Bluetooth module connector to be noted.

Is there a good way to measure a high-side shunt in the new design I will make without an isolated op-amp?

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  • \$\begingroup\$ Is R141 rated in excess of 10 watts? Maybe the whole of the monitoring circuit is floating? \$\endgroup\$
    – Andy aka
    Feb 20, 2023 at 15:10
  • \$\begingroup\$ no, it's a normal 1/4 w Res! yes, All the control and monitor circuit is floating because it is isolated. \$\endgroup\$ Feb 20, 2023 at 15:12
  • \$\begingroup\$ Then the whole of the monitoring circuit must be floating and won't care if it's grounded at one point to the 450 volts. \$\endgroup\$
    – Andy aka
    Feb 20, 2023 at 15:14
  • \$\begingroup\$ The circuit is 2 PCBs above each other and in the size of a 12" tablet, connecting the GND of the whole thing to a 450V potential just to be able to measure a high-side shunt is a very strange idea to me. \$\endgroup\$ Feb 20, 2023 at 15:19
  • \$\begingroup\$ @JRE thanks for the corrections \$\endgroup\$ Feb 20, 2023 at 15:37

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