SSPA Power Supply - New Thermistor Success!

The new 10 Ohm 18 amp Thermistors performed exactly as I had hoped.  Actually they really exceeded my expectations.  With no step/soft-start 4 of the dps-1200fb's starting up at the same time consume nearly 11 amps of inrush @ 240 vac.  My Supply has 8 of them so that would be abut 22 amps of inrush.  I'm not really comfortable with that much, it's not terrible, but I just didn't like it.

So...I setup a step start that uses Thermistors and a relay to short around them after 3 seconds.  3 seconds is way longer than what's needed, but it just happens that the timer delay's I have start off at 3 seconds, so I'm using them.  It's not hurting anything to let the Thermistors be inline that long.  A lot of designers don't even bother to short around them with a relay.  Thermistors get pretty warm under a load, and if they're hot when the system is turned off, they won't have enough resistance to perform a soft start.  As they got hot they gradually loose almost all their resistance.  

The relays I'm using short around them after 3 seconds allowing them to remain and stay cool so that if them amp has to be turned off and then on again immediately, the soft start will work every time.

SO....to the details...

I replaced the 1 Ohm Thermistors which were getting inrush around 8.5 amps.  I replaced them with 10 Ohm today and the results are really pleasing.  1.4 amps!

And that's repeatable over and over.

SSPA Power Supply - Larger Thermistors

I am swapping out the 1 Ohm Thermistors for some 10 Ohm's.  The 1 Ohm's seemed to only just barely dip the inrush.  I'm looking for something more dramatic.

So we'll see how this effects inrush.  These new ones are 18 amp 10 Ohm.  The 1 Ohm's were rated 30 amp.  

I went about this all wrong to start with.  And I'm learning as I go so please don't laugh too much. :-)  I've never used Thermistors before so this is mostly just so I can have some hands on real world exposure to using them.  

Truth is I don't really think I need this step start / soft start with this power supply.  But it certainly won't hurt anything, and it gives me a chance to learn something new that I'm sure I'll be able to use in the future.

Anyway 1 Ohm @30 Amp Thermistors only dropped inrush by about 1.5 amps @240 vac. 
I'd like to see total inrush really dropped by like 50% or more if I can.  Total inrush was 8.5 amp with the 1 Ohm's.  I'd like to see that cut in half or even more.  

But gut says this still isn't enough to do that...but we'll see.  Here are some pix.  

The 10 Ohm thermisors are the large ones in the photo's below.

SSPA Power Supply - Larger Thermistors

I am swapping out the 1 Ohm Thermistors for some 10 Ohm's.  The 1 Ohm's seemed to only just barely dip the inrush.  I'm looking for something more dramatic.

So we'll see how this effects inrush.  These new ones are 18 amp 10 Ohm.  The 1 Ohm's were rated 30 amp.  

I went about this all wrong to start with.  And I'm learning as I go so please don't laugh too much. :-)  I've never used Thermistors before so this is mostly just so I can have some hands on real world exposure to using them.  

Truth is I don't really think I need this step start / soft start with this power supply.  But it certainly won't hurt anything, and it gives me a chance to learn something new that I'm sure I'll be able to use in the future.

Anyway 1 Ohm @30 Amp Thermistors only dropped inrush by about 1.5 amps @240 vac. 
I'd like to see total inrush really dropped by like 50% or more if I can.  Total inrush was 8.5 amp with the 1 Ohm's.  I'd like to see that cut in half or even more.  

But gut says this still isn't enough to do that...but we'll see.  Here are some pix.  

The 10 Ohm thermisors are the large ones in the photo's below.

SSPA Power Supply - Feedthrough Capacitor

I discovered today that Corcom (now TE Connectivity I guess) made/makes DC Feedthrough Capacitors.  Below are some specifications on the one I'm interested in.

The one I was initially interested in is the 200DFC6-R but I found a batch of 200DFC6-P's for sale at > 50% off new prices on Ebay.  New these run about $165.  The ones I found on Ebay are listed as "New Unused" and cost $75+$6 shipping.  Still a bit pricey if you ask me.  But I think worth a try since between 10-100 MHz Insertion loss is between 50-90db!  90db at 100 MHz.

The "P" model is 1000nF, the "R" that I wanted is 4700nF the "R" model is 70-90db between 10-100 MHz.  

It's good to know these are available at least.

I've ordered the 200DFC6-P from Ebay.

These things are small tho so may be interesting figuring out where to place things around it.  Nearly 6" long and 1.5-2" wide.

Top row is in inches, bottom in mm.

Here's part of the datasheet on them.  Click the image for a large copy or go here to download the whole thing.

SSPA Power Supply - Teflon

Added Teflon sheet to bottom shelf.

SSPA Project - 50Vdc @ 200 Amp - First Power ON

"Smoke test" = OK :-)  So that's good.  I didn't mux anything up.  I checked and tripple checked everything.  Trying NOT to explode anything.  And that effort appeared to pay off.

I worked most of the day on getting things ready to fire up tonight.  The only thing I don't have wired up is "bank2" as well as the Ammeter.  I have the shunt, and wire just have to wire that all up.  I'm waiting for some large battery posts to run DC wire out of the case.

So there are basically 2 'banks' (1 and 2) each 'bank' had 4 dps-1200fb supplies running 12.5vdc in series.  Which equals 50.0vdc.  Then the two banks are setup in parallel.  Each bank is capable of 100 amps, combined the entire system is capable of 200 amps.

The new Step-Start works, but needs some tweaking.  It has the INRUSH down from 11 amps to 8.5.  But I think with some more attention to it I can get that down below 1/2 of that.  I didn't have anything setup as a jig to test that function until now, so I should be able to make some good progress on that.

I'm using 2 AWG to run < 6 ft up to where the Amps will be located.

Here is a video showing the state of things during the test.  And how it went.

SSPA Project - 50Vdc @ 200 Amp Distribution Blocks

SSPA Project - 50Vdc @ 200 Amp Panel Meters

Inexpensive 12vdc LED string (Blue)

SSPA Project - 50Vdc @ 200 Amp Power Supply UPDATE

Top left to bottom right....

40A 240v Relays on heatsinks

40A 240v Relays w/Thermistors (relays short after 3 seconds)

Center 240v 60A EMI Filter

400A/50mv ammeter shunt

250A Distribution Block

12vdc Supply

(2) Timers (for 40a/240V RELAYS)

-------

(4) dps-1200fb (2 banks) 

SSPA Project - 50Vdc @ 200 Amp Power Supply UPDATE

Top left to bottom right....

40A 240v Relays on heatsinks

40A 240v Relays w/Thermistors (relays short after 3 seconds)

Center 240v 60A EMI Filter

400A/50mv ammeter shunt

250A Distribution Block

12vdc Supply

(2) Timers (for 40a/240V RELAYS)

-------

(4) dps-1200fb (2 banks) 

SSPA Project - 50Vdc @ 200 Amp Power Supply CASE

Over the weekend I started building the case for this power supply.  It's a 4U Computer Server Case that I got for $70.00 off Ebay from NewEgg.  I gutted it completely and using some aluminum angle stock I made some pseudo rails.  Using bits from the guts that came with the case I was able to 'stack' the dsp-1200fb's so that air can flow around them a bit, and still gives me room for other things require to operate this power supply.

Here's some Photos of where the project is now.  Everything is still rough as I'm just test-fitting all the bits and pieces still.  But you'll get the idea.

SSPA Project - 50Vdc @ 200 Amp Power Supply CASE

Over the weekend I started building the case for this power supply.  It's a 4U Computer Server Case that I got for $70.00 off Ebay from NewEgg.  I gutted it completely and using some aluminum angle stock I made some pseudo rails.  Using bits from the guts that came with the case I was able to 'stack' the dsp-1200fb's so that air can flow around them a bit, and still gives me room for other things require to operate this power supply.

Here's some Photos of where the project is now.  Everything is still rough as I'm just test-fitting all the bits and pieces still.  But you'll get the idea.

SSPA Project - DPS-1200fb INRUSH TESTING

Just got my Fluke 376fc Meter.  Tested INRUSH on four of the HP dps-1200fb supplies being turned on at one time.

Results ranged between 9.5 and 10.9 amps @ 240v.  Once INRUSH is over they settle down to <= 1 amp.  So for 8 of them these numbers would be 2x.

In case your curious how I did this...here's a short video...(warning it's a little clumsy :-)

SSPA Project - DPS-1200fb 50VDC (200 AMP!) - Well almost

So I've got the hard work done on the 200 amp 50 VDC supply.

Believe it or not making those #6 AWG battery cables was like hard labor.  Crimping them with a small hand crimper then soldering them....sucked.

So the next phase of this is two get the step-start built, and I have to run a second 240v line to the shack.  I'm going to use 2 each 240v @ 30A lines to run this supply.  

I'm still thinking about my options for mounting all of this.  I have a large 4U computer server case I could use...it'd be kinda nice for this as it has built in fans already as well as dust filters (a must here!).  That's probably what I'm going to use.

It took me about 48 hours (with sleep mixed in there :-) to modify all of these and create the jumpers.

SSPA Project - DPS-1200fb 50VDC Smoke Test Results

Today I make my mini-jumpers from #6awg and lugs, and wired up the Main and it's 3 "Floaters" (DPS-1200fb's).  Plugged the DPS-1200fb's into my new PDU which was plugged into the 240vac outlet.  Turned it on, and wah-friggin-lah 50VDC!

Smoke Test Video

SSPA Project - DPS-1200fb "floater" mods

This set of mods creates a 'Floating' Supply.  Where the 12.5v output ground is not connected to the case.  This is a requirement for 3 of the 4 supplies in the 50v series I'm building.  This page describes what I'm doing somewhat.

Here's a video showing ever detail...

First thing to do is add a 500-1000 Ohm Resistor between these two pins.  This enables the device.  Simulating what would occur when it's placed inside a computer server case.

Top right adjustable pot (in the string of 3 above my thumb, top of the board).  Adjust this from stock 12.3vdc to 12.5vdc.

Next dremel off the metal stand off's and then lightly drill them until the remainder falls out.

  Add some nylon bolts, spacers, and nuts

Add lugs that'll be used to make power connections