I hope all goes well in your kludge'pedition. Dodging bullets can be a demanding task.

I'm not sure if you are looking for a characteristic of the SCR's or just a part number. The part number they are labeled with is N023RH12. Then there's the small logo and another bit of text "B020."

Westcode Semiconductors
"Convertor Grade Stud-Base Thyristor Type N023R"
PDF Datasheet - N023RH12.pdf

Regarding the BAP1950's J5 connector and its three-phase references lines, the lines should be disconnected from the brake circuit when the BAP1950 is not live and in control of the SCR's?

Are the three lower diodes installed to work as quenching diodes, like would be used in an automotive relay setup? (Possibly called a suppression diode)

I ordered the BAP1950 and the NI USB-6211. The BAP1950 will take four weeks to arrive. The DAQ should be here within five business days.

 

They are good for 1500 volts and 48 amps. I will see about finding some diodes to match the current, but at 600 volts.

Probably a good idea to disconnect those lines when the BAP1950 isn't controlling.

Without some info on the functioning of the BAP1950, I'm not certain why they want them there.

You may need a box to hold the diodes plus the relays. The diodes will need to be mounted on heat sinks - they will be stud mount devices. I'll get you some details. The sinks will be about 4 x 2 inches, and stand another 2" high.

Still having fun - this is a prototype unit, and it isn't really all that functional. What I get for a low quote.

 

Well, that was fun. Vishay makes rectifiers big enough to do the job. Their 70HF(R) series are DO-5 stud mount units. Digi-Key has them as part # 70HFR80 @ $12.10.

I think one heat sink also from Digi will mount them. That's part # 345-1050 @ $19.33. The flat channel is 5.4" long, so it should hold all three diodes. You'll also need 6 pieces of #BER105 insulating washer @ $.88 (or 10/$.79).

The fun part is insulating the studs passing through the sink. I can't find mounting kits anymore - they used to have mica washers plus a teflon insulator that fit over the threads so the stud didn't short to the heat sink. Or you could get teflon washers to stand the heak sink off with so you could just thread the mounting hols for the diode.

Anyway, be careful to meter the diodes to insure they are all insulated from the heat sink, or lots of factory smoke will come out. And we thought this would be easy...

 

I updated the NewDynoControlBoard schematic to include a 3PST relay inline with the three-phase monitoring lines connected to J5 on the BAP1950.

Jan. 19 NewDynoBoard Schematic (jpeg)

I checked out the 70HF diodes on DigiKey. They look serious. The heatsink looks good too. Regarding factory smoke, iIn a relatively high vibration environment, won't the diode studs move within the center of their holes in the heatsink? Some of the big diesels really shake the place. The insulating washers would take care of the top and bottom, but the threads in the middle are exposed like you mentioned.

When faced with a similar decision with mounting the big SCR's, the Sicon techs chose to electrically connect the SCR's to the heatsinks and insulate the heatsinks from the case. The closest thing I could find to an insulated stand-off on Google was a piece from RadioShack. On the other hand, what worked for them in that particular situation may not be the most practical approach now. If the stud and nut are tightened down well, they're might not be any problems.

A picture of the insulated standoffs in the original eddy current controller box.

 

Yeah, those are really gnarly. The kind of heat sink I suggested mounts nicely with those no-longer-available teflon washers. And it is so nice to just tap in the diode and the screw to attach the wire terminal.

Well, a trip through the old Newark Electronics (sort of like McMaster-Carr for electronics) found part #09WX0134. Those are mounting kits for DO-5 stud mount diodes that include the insulating sleeve to keep the threads off the hole through the heat sink. All of $0.26/ea.

Otherwise, look up the drawing for a Wakefield sink and get grommets (Newark page 2093) to fit. They have enough heat sinks to cross your eyes, too.

 

I'm trying to get a better understanding of the purpose of the three regular rectifiers. This is what I have found on Google so far.

Semi-Controlled Rectifier Circuits

 

Control and Power Electronics Java Applets

 

I drew up a schematic showing how the BAP1950 SCR Firing Board will connect to the main portion of the eddy current brake coil circuit.

January 22nd, 2009 - Brake Coil Circuit Schematic

I tried this one in LTSpice after doing the last few in Photoshop. What a difference. Creating custom symbols is nice and straightforward.

The above link shows the circuit as it appears on the original Sicon Eddy Current Dyno Controller schematic. The next link shows a different version of the simplified schematic that incorporates the "bottom half" diodes called for in the BAP1950 example diagram.

January 22nd, 2009 - Brake Coil Circuit *With Diodes* Schematic

Is there any way to know for sure if adding the diodes is necessary? Then the second part, is there any recommend approach to determining what the effect of adding the diodes on the existing manual control circuitry will be?

I'm going to try emailing the Applied Power Systems engineering staff to get their input as well. I won't hold my breath for a response.

 

In the first appearance, I thought the added diodes were on the other side of the brake, with their cathodes connected to the SCR's anodes. It would be good to determine which arrangement is correct.

Beats me if the manual control will even notice if they are there. I think it may use the 38 volt transformer as the phasing reference. I still have no idea how it sets firing angle for the SCR's. I suppose you can always place them in circuit and see what, if anything, happens. Do that before wiring in the new controller.

APS should be able to give you a rational reason for the diode addition.

 

I took another look at the half control example diagram from the APS BAP 1950 manual. It looks like the new diodes are in the right place. What I may have to change are the connections for J5. The example diagram shows them tapping into the circuit closer to the three-phase source, not in-between the diodes and and SCR's.

The sites linked a couple posts above mentioned that the "bottom half" diodes counteract a bit of hysteresis caused by the inductive load. That's probably a poor, possibly inaccurate description on my part, but I don't know exactly what to call it.

Is it possible there are similar diodes located inside the multi-phase converter? I can take a look at it tomorrow, but I figured I would ask in case it might be a common occurrence.

 

I spoke to Les at Applied Power Systems. He printed out the simplified brake coil circuit schematic and is going to look it over. On first glance, he said he saw no reason why it wouldn't work but wanted to take more time to make sure. I asked about the J5 reference lines and he said they're fine the way they're currently drawn in.

The NI USB-6211 showed up yesterday, as did a few of the parts from Mouser. It will still be some time before the BAP1950 is ready. If the schematic proves to not be a problem, there will be time to work on the data acquisition and LabView side of the project.

 

I ran up a schematic of how I imagine you would use the relays to switch signals.

 

Wow, now that's a real schematic. It manages to show all parts of the circuit on one page and in a manner that's easy to understand. Thanks, that helps a lot.

Looking at the schematic, I'm guessing you think it's a bad idea to leave the 380V three-phase reference to the 6'024'0 circuit live when switched to "Computer Control" mode? While it's not a big deal, in terms of difficulty of the real-world change, to cut the 380V reference connection to the BAP1950 when switched to "Manual Control," it's a bit more difficult to do the former. The 3-phase references lines to the 6'024'0 circuit are actually metal studs that physically attach the 6'024'0 circuit board to the three large R, S and T aluminum heatsinks. This picture shows the studs electrically connecting the heatsinks to the 3-phase reference terminals of the 6'024'0 circuit. Nothing is impossible, but it would require more than traditional rewiring. A non-conducting plastic stud could be used, and a fourth Mil Spec connector could be added to the Sicon box.

Is D1 the not-yet-installed diode that would make the current Sicon eddy current brake coil circuit resemble the example BAP1950 half-control circuit?

Les at Applied Power Systems got back to me and said the January 22nd, 2009 - Brake Coil Circuit Schematic would work with the BAP1950. He was not a big fan of the January 22nd, 2009 - Brake Coil Circuit *With Diodes* Schematic. This surprised me a bit because I designed the second *With Diodes* schematic to more closely mirror the example BAP1950 half-control circuit. Either way, Les said to use the base schematic without diodes so that's most likely what will be done.

Is CB1 is the relay labeled A05 on the original Sicon controller schematic?

I started adding the new wires and connectors necessary to add switchable computer control to the dyno. The connectors and wires follow the January 17 - Modified Sicon Controller schematic.

Sicon Controller Box Modifications Part One

Sicon Controller Box Modifications Part Two

The original plan was to use a tool that electricians use to punch new holes in electrical boxes, but we couldn't borrow one in time. The general purpose three axis mill couldn't fit the Sicon box. We had to get a bit silly. I forgot to ask what the big green machine is normally responsible for.

I'm interested to hear what you think about the 380V reference wires for the 6'024'0 circuit.

 

In no particular order:

Good, I could not see the point of those added diodes.

Yes, CB1 is part of A05. I may have misinterpreted it as a circuit breaker. I have worked with German and French schematics, but this is my first Italian one.

Why use a slug punch when you have hole saws? No one can hear the chatter over the engines under test.

No, I don't have any problems leaving the 380 volt lines into the old controller in place. I simply switched them with the relay as with the other lines. They can just be switched over to the BAP 1950 as needed through a set of contacts. The BAP 1950 should only use the lines as a phase reference, so light wiring is in order. Check with them, but 16 ga should be way enough.

i should probably think of other intelligent things to comment on, but I have been designing a new PCB and my brain is a bit full. I'll try to look this over again tomorrow.

 

Had to work on a separate job last week. Back to work on the dyno starting yesterday. I spoke with Les at Applied Power Systems and the BAP1950 board might be ready as soon as this Friday. There's no guarantee, but it's sooner than expected which is good to hear.

I started planning the new rackmount enclosure that will house both the data acquisition and SCR control parts. It looks like there will be at least seven connections on the back panel. On the front, there is currently only the illuminated rocker switch for selecting manual or computer control.

Data Acquistion
* Load Cell (Force -> Torque)
* Variable Reluctor (RPM)
* USB (PC Connecdtion)

Dynamometer Control
* Manual Input (Manual Controller Output Signals)
* SCR Control (SCR Input Lines)
* 3 Phase Ref (Three-phase References Lines)
* 120 VAC Supply (BAP1950 & Relay Power Supply)

A rackmount case was ordered from Mouser. It's a "BUD Rak-Mount Chassis" that's 5.25" tall and 17" deep, with a solid bottom panel and vented top panel. This is the respective Mouser catalog page. (pdf)

Mouser Stock No.
* 1x 563-RM-14212 - Front, Rear and Side Panels
* 1x 563-TBC-14252 - Solid Bottom Panel
* 1x 563-TBC-14262 - Vented Top Panel
* 2x 563-H-9111-B - 4" Front Panel Handles

Aluminum standoffs were also ordered to mount the BAP1950 0.75" off the base of the rackmount case. The BAP1950 mounting holes are 0.171" in diameter and so should fit 8-32 screws. I checked with Les and the holes in the circuit board are insulated from the rest of the circuitry. The grounds and other traces supposedly do not come near. If the head of the 8-32 screw proves too wide, 6-32's and new standoffs can be used.

Also order Tyco AMP Mate-N-Lok connectors for the connections to the BAP1950 board. J3 is a 12 pin Mate-N-Lok, and J4 and J5 are 5 pin Mate-N-Lok's.

There are going to be a lot of different wires in the enclosure. Any recommendations on an effective labeling system?

 

We always used peel-off wire markers, but they fall off with time. India ink on a white sleeve under clear shrink-fit would be good.

 

Ah, that's a good idea. I'll have to pick up a bit more clear shrinkwrap.

I spent a bit of time on Google looking at what's used commercially and I found that just a label printing machine itself costs around $700. Then there's the label supplies, ink and other parts that probably bring the total around one thousand. If I were going to make lots of these, it might make sense, but not for a one-off.

I realized last night that I hadn't ordered a 3PST relay for the BAP1950 3-Phase Reference connection. I checked the Omron MK Series white paper and they don't seem to have a plain 3PST relay. I have three MK3P5-S relays. Can I use a 3PDT relay as a 3PST relay by not connecting anything to the "Normally Closed" terminals? It seems straightforward and likely to work, but I've made simpler incorrect assumptions before. Should that be okay?

 

If the contacts are good for the voltage and current, there should be no problem. Your controller shouldn't draw much at all.

 

Thanks, I forgot to check the voltage capacity. I'm lucky you mentioned it because the MK relay's voltage rating is indeed insufficient.

Omron
General Purpose Relay MK
Specifications
CONTACT DATA
Max. operating current 10 A
Max. operating voltage 250 VAC, 250 VDC

Now to look for a 3PST relay with a higher voltage rating.

 

At first, it looked like the inexpensive and abundant, off-the-shelf industrial relays only ran up to 220-240VAC. I found a few Hartman relays that handle 380VAC, but they were $3,000-$7,000+ pieces designed for aerospace applications. Unless the next Mars rover sports a CAT 3116, I think we are going to have to pass on that one.

Hartman B-312CS, 100A @ 380VAC Contact Rating

I started digging through Google searches for a "380VAC relay" and found another relay product line from Omron. The "General Purpose Plug-In Relay, MJN Series" fits the bill.

Push-to-operate button & LED indicator
3PDT
MJN3C-IN

Omron MJN3C-AC120 3PDT Relay

UL and CSA recognition as motor controllers through 600 VAC.

10 amp @ 28 VDC and 120/240 VAC at 80% pf, 1/3 hp @ 120 VAC, 1/2 hp @ 277/240/480/600 VAC
36 LRA--8.5FLA at 18 VDC, 3 amp @ 480/600 VAC at 80% pf, 10 amp @ 277 VAC resistive

It's great to find another Omron relay since the other two relays are Omron pieces, but also because Omron provides CAD drawings for their relays.

There's the MJN socket also.

Omron PTF11PC MJN Series Plug-In Relay Socket