100VDC Bus and arcing contacts in connectors?

[Flyback]

Hello,

We are supplying twenty 10W LED lighting fixtures from a 100VDC bus.........is it true that when we connect a fixture to the 100VDC bus, there will be such severe arcing between the metal contacts of the connector that the connector will not last more than a few months?

Can we alleviate the problem by using some kind of inrush protection , whereby the arcing current is limited by a resistor which gets switched out after the initial arc?

 

[tcmtech]

At .1 amps and not being a highly capacitive or inductive load it's not likely to be an issue.

 

[Flyback]

I think it is an issue because there will be inrush into the input capacitor of the LED lamp....

Does the attached schematic offer a solution?.....ie it gives us a chance to make the contacts when there is no current flowing because the PFET is OFF........then there can be no contact arcing because the contacts are already closed before current starts flowing?

Non arcing HVDC switch?
https://i44.tinypic.com/23wryba.jpg

Also scm attached

 

[alec_t]

If the input capacitor is the 22uF shown then inrush protection is hardly justified IMO.

 

[Flyback]

..but the input voltage is 100V DC..and as we know from the failure of the 42V auto system, DC voltages of >24V are not practical and cause severe arcing in switches/connectors. AC is different, as every 20ms it goes through zero, and the arc is extinguished then.

 

[alec_t]

The energy to charge 22uF to 100V is ~110mJ; not enough to cause significant heating of the connector contacts. Charge time is likely to be less than 1ms (dependent on source impedance).

as we know from the failure of the 42V auto system

You might know, I'm afraid I don't . Can you post a link?

 

[tcmtech]

..but the input voltage is 100V DC..and as we know from the failure of the 42V auto system, DC voltages of >24V are not practical and cause severe arcing in switches/connectors.

It all depends on the design. I work on large industrial electromagnetic crane systems and they are typically running 280 - 320 VDC open circuit system voltages and switching between 50 - 80 amps of highly inductive loads with nothing more than big mechanical double pole switches and all of the control circuits run at the same system voltages as well using normal open frame type relays.

To me switching 100 VDC at .1 amps is trivial at best. If it was me I would just put a 50 ohm resistor in series with the load that would limit the inrush current to 2 amps but at .1 amps load current would only produce a 5 volt drop and 1/2 a watt of power loss when the circuit is running.

Personally I think you are just way over theorizing and engineering a simple circuit.

 

[Flyback]

Hello,
I think you all have underestimated the problems of switching a DC voltage of 100V.
(the average involved current is low, but its that initial sparking that does the damage)

The following is a spec for a worldwide proposed 24V lighting system....
https://www.electro-tech-online.com/custompdfs/2013/06/dg_cl_24vdc_emerge.pdf

...it would be more efficienct if it was a 100V DC bus, but they chose 24V for the sole reason that 24V gives manageable break/make contact sparking, and the involved damage to contacts that this causes.

 

[ronv]

What is the source impedance of the DC buss?

 

[ronv]

If there is time between plugs a thermistor would work.

https://www.electro-tech-online.com/custompdfs/2013/06/cantherm_mf72.pdf

 

[Flyback]

What is the source impedance of the DC buss?

Its the output of an LLC resonant converter, so it'll be low, due to the output capacitor bank.

 

[ronv]

What do you think about the thermistors then? Little less burdensome than the PFET.