100VDC Power bus for LED lamp supply

[treez]

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?

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

 

[betwixt]

If you are talking about arcing across the 100V bus, as long as the contacts are say 0.5mm apart there will be no arcing.
If you mean inrush current as the connectors meet, there may be some arcing but if the LEDs are the only load it shouldn't be severe. LEDs will appear as a resistive load which is probably the least damaging kind. If in doubt, add an NTC thermistor in series with the feed, it will slow the rise of current until it reaches working temperature.

Brian.

 

[treez]

If you are talking about arcing across the 100V bus,

..i dont mean that

If you mean inrush current as the connectors meet

..yes, thats what i mean


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.
An NTC will not be useful at these low average current levels..........yes it will quell the inrush , but then it will be too lossy.......10W = 100V * 0.1A....and 0.1A is too low for an NTC.

 

[betwixt]

In that case an electronic inrush limiter is the solution but I'm not sure a 'manual' start switch is the best way to do it. Probably your cheapest solution is to use a relay with it's coil current delayed a few mS by connecting a capacitor and resitor network in it's supply. Connect the NO contacts in series with the LEDs and bridge the contacts with a resistor of a few Ohms. At insertion, the resistor will limit the current and after a few mS the relay will short it out and give full current flow. It can also be done solid-state but would probably cost more.

Brian.

 

[treez]

Emerge alliance have already given up with the 100V DC bus, and have chosen a 24V DC Bus, precisely to avoid contact sparking....
https://www.crestron.com/downloads/pdf/product_misc/dg_cl_24vdc_emerge.pdf

...are they missing a trick?, why dont they use your discussed inrush tricks and get round contact sparking like that?

 

[betwixt]

Within reason there is no reason why any voltage can't be used. Higher voltage generally means less current and vice versa so one can be traded against the other. Higher voltages pose a greater risk to someone touching them and higher current poses a greater heating risk if shorted out. You should note that there is no inrush current to LEDs themselves but there may be an inrush current to LED inverters. For the most part, the models shown are for selectively controlling LED lighting though, they offer greater flexibility where large areas are covered and it is impractical to place power switches at every point that could need controlling.

Brian.