WS-12-250-DC - Watt/Amp/Volt

[eomedia]

I guess I'm not certain how to confirm this. The WS-12-250-DC switch can take 9-60 VDC power with a 250 watt power supply but can output 48V powered radios - so to accurately predict the Amps under full load I'm guessing that I need to use the VDC IN value for calculation regardless of what the switch does with it.

24V input at 250w = 10.417 Amps max

The reason it's important is because I want to utilize the TPDIN-Monitor-Web (http://tyconpower.com/products/files/TP ... _sheet.pdf) unit to ping/power cycle the switch if needed and the relays support 10A 30VDC which is kind of on the borderline of my math. I can of course always lower the usage on the switch to ensure it's under the value but I want to check with someone who understands this a little better to confirm.


Thanks

[sirhc]

Yes you can power the WS-12-250-DC with from 9V to 60V and it can power 24V and 48V devices.

The table below shows the capacity at a given input voltage.

The full 250 watts is available with as low as 12V DC input.

CLICK IMAGE BELOW TO VIEW FULL SIZE

eff.jpg (69.22 KiB) Viewed 12234 times

The DC to DC power supply has it's own microprocessor and firmware and is in constant communications with the switchboard and it's firmware and if needed will shut down ports to preserve integrity as input voltages drop.

The user specifies POE port priorities so the switch will shut down less priority ports in an attempt to remain up as long as possible as input voltages drop or the unit begins to overheat.

The switch reports the input voltage and watts being supplied by the batteries.

[eomedia]

I think I understood all that, I was more along the lines of understanding what the AMPS would be so that I understand if I'm going to exceed the 10A level of the TPDIN relay. Is the AMPs being drawn by the switch always determined by the input volt/watts used regardless of whether it's outputting 24V or 48VH at the end of the day?

[Dave]

Hi, I am currently out of town & do not have my data with me, but your equation needs to take into account the efficiency of the dc-dc converter, so the fuse rating required for a certain load will also depend on the input voltage (and load of course).

So, using your 24 volts input at 250 watt load, according to the graph efficiency is about 92%. so equation should be:

Amps in = (Power/Vin)/effiececny

Amps in = (250 watts / 24 volts) / 92/100

Amps in = 10.42/.92

Amps in =11.33

But in reality, I doubt anyone will be using anywhere near that heavy a load, but same equation format will apply.

[lligetfa]

But in reality, I doubt anyone will be using anywhere near that heavy a load, but same equation format will apply.

I'm not sure if the OP is looking at worst case scenario or doesn't understand that the amps drawn will vary by the loads the switch will power. Who in their right mind would run at the max 250W load anyway?

Dave, how much should one factor for inrush? I realize that the PoE out is staggered a little to minimize it and each radio will have its own startup characteristic.

[eomedia]

I'm really looking at worst case scenario - I would not expect to be running at full power but I would like to understand how the calculation would work. I'm looking to increase my understanding a bit here and hopefully apply that knowledge going forward.

[Dave]

Les

I am out of town & will be back next week, so I will post up actual inrush numbers then. But just for everyone's info, inrush current is controlled, we basically have a 3 step approach. As soon as someone connects power to the front panel terminals, our main bulk capacitor charges, then after a few seconds, the main controller is enabled, it then ramps up the output voltage slowly ( few milliseconds), and then the switch powers up & will sequence ports on one at a time.

Dave