Electrical – Mechanical Contactor for High Voltage DC – Substitute with Semiconductor

contactorhigh voltagemosfetsolid-state-relayswitches

To switch 1kV DC at 5A, I usually use a mechanical contactor (<- Wikipedia) that switches both highside and lowside of a resistive load.

Any suggestions on a semiconductor (or non-mechanical part) to do the job? For me, especially the high side switch makes it difficult.

Both highside and lowside have to be switched to meet the guidelines.

Schematic

Best Answer

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Combined relay / switch + SSR.

Keep the relay or switch for safe isolation and lockout. A high-voltage DC SSR can be installed on either or both legs of the circuit. You need to meet:

  • Blocking voltage (> 1k V and maybe > 2 kV for safety) for your 1 kV supply.
  • Isolation voltage (> 2 kV) to prevent insulation breakdown between the high voltage and low voltage circuits.
  • Switching current (> 5 A) and allow for any surge due to cold resistance of the load, etc.).

A quick search found Sensitron devices, for example.

Your control system can now turn on RLY1 and leave it on in normal operation while using the SSR for normal control. This gives you the advantages of low cycles and wear and tear on the relay while maintaining the ability to isolate safely.

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