Puppeteer

Author Topic: High Volt/ Amp DC Switching hacks.  (Read 5949 times)

veggie

  • Keep Calm and Start the Lister !
  • Hero Member
  • *****
  • Posts: 843
    • View Profile
Re: High Volt/ Amp DC Switching hacks.
« Reply #15 on: March 08, 2019, 07:15:14 PM »
Better test that 12V auto starter relay very carefully; gods only knows how well it will work on 300VDC or whatever your PV string voltage is.

My Solar array is 24-36 volts depending on load, and my heating element is a 600 watt, 24 Volt unit with the impedance matched to the array output sweetspot.
Max amps is around 27. I don't see any fire risk with the solenoid being this underloaded. And it is a dedicated DC switch.
The application would be different for everyone but for switching of <100 amps at 12 to 24 volts these units have proven themselves for decades.

They are standard equipment on wind turbine and solar array Load Diversion modules.
« Last Edit: March 08, 2019, 07:25:10 PM by veggie »
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw
- Changfa S195 (Waiting for a project)

BruceM

  • Hero Member
  • *****
  • Posts: 3054
    • View Profile
Re: High Volt/ Amp DC Switching hacks.
« Reply #16 on: March 08, 2019, 09:31:07 PM »
No issues at all for low voltage DC systems using low voltage DC contactors.  They were designed for it, and raising voltage while decreasing amps should be fine. Both voltage an current affect DC arcing so if you are in the voltage range the device was designed for, at lower current, all is well.

It is a different matter for higher voltage DC at moderate currents, the arc length can be quite long, making current interruption a challenge. The relay products designed for it often use permanent magnets to bend the arc to a longer path, and multiple contacts to increase total arc length so the arc on opening will extinguish. 

I've blown lots of switches, breakers and contactors messing with my nominal 120VDC (up to 156V). My home and shop are 120VDC powered, with the shop also having generator or inverter AC.    I used Cooper brand switches that were rated for 150VDC in my house, but those are no longer available.  The Leviton rotary light switches date back to Edison's (110VDC) time in design, and I've tested them for hundreds of cycles switching 4 amps, and only use them for 1 amp.