The relative sizes of Wire-Gauges, on the various Windings of the Transformer,
provide a good indication of how much Current that particular Winding is supposed to handle,
as the Current-Capacity goes up, the expected Voltage in that Winding goes down, and vice-versa..

For the purposes of identifying the probable purpose of the Windings ..............
You can think of every Winding as having the same Power, (VA), (Watts), rating,
and since Volts X Amps = Watts ..............
If the Winding is designed to work at a High-Voltage,
then the Winding-Wire will be sized for a lower-Current, (Amps), ( smaller-Wire-Gauge ),
lower-Current means that the Voltage on that Winding would have to be higher to
make the above Math-Formula equal the maximum Power-Rating of the Transformer.
This Winding will usually be the "Primary", or "Mains-Input", Winding,
which may be split into 2 equal Windings to accommodate different Mains-Voltages, ( usually 120V / 240V ).

But if the Winding has has a larger Wire-Gauge,
then it is intended for more Current, and therefore lower-Voltage,
to make the above Math equation equal the maximum Power-Rating of the Transformer.

It is possible to make a "vague guess" as to the Transformer's Secondary-Voltage-Output by
comparing the difference in Wire-Sizes between the Primary and Secondary Windings.
You should actually measure the Wire thicknesses, in Millimetres, with a Caliper, and write them down.

A "Battery and a Light-Bulb" type of cobbled-up "Continuity-Tester"
is sometimes better than an expensive Digital-Multi-Meter for doing this job.
Print this out and start taking notes ..........
It's in both PNG and PDF 8X10 formats for Printing.
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We already know that the transformer is intended to supply either 12 volts or 24 volts after the rectifiers. That comes from the one instruction listing. So that is the high current connection. The question is about the primary, which we know will work with 240 volts, but may actually also be adaptable to 120 volts, by connecting the two halves in parallel.

My plan would be to first discover the current arrangement, and what terminals the 240 volt mains power is connected to. This means not losing information by disconnecting wires, until all of the information is known clearly!

 

@Rocketman12 , did you even look at the link in post #37? they have already went down your path and figured things out.

 

@Rocketman12 , did you even look at the link in post #37? they have already went down your path and figured things out.

He doesn't have a "100-Amp Russian-Battery-Charger" to work with.
The available Transformer needs to be figured-out and measured to have a starting point.
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He doesn't have a "100-Amp Russian-Battery-Charger" to work with.
The available Transformer needs to be figured-out and measured to have a starting point

Doesn't need to be that particular thing just that kind of thing.

I must have missed the point where he said he took his retarder apart and rewired it so the high voltages you and billy keep suggesting will work. The original link to the retarder in question is kind of specific on how it needs to be wired when using the original coils. Letting the smoke out of someone else's parts, that will cost money to replace isn't what I would ever consider doing but you two don't seem to be bothered by it. And because the two of you are going along with the TS from the get go he thinks what you guys are both telling him is OK. And I disagree.

And to start with something that has already caused problems and burnt the circuits? That should be a hint something is wrong from the get go. A link to someone doing this and making it work would be something I would follow or at least look at before changing to a higher than normal voltage. There are many links to people doing this but I'm not going to keep wasting my time fighting with the "real" experts.
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It was me who suggested rewiring, based on very specific information provided in the OEM' spublication. AND, the portions that have failed and burned up were the instrumentation and controls circuit boards, which have now been replaced by a small computer.
The concept still is to use the connection scheme provided by the OEM to connect the three sets of coils each as three 24 volt series connected sets. of coil pairs, and then connect those three sets in series. I am really not sure why that is so complex or so confusing. Three loads in series, with each load requiring 24 volts, will need 72 volts to draw the rated maximum current.

Then, to vary the retarding torque from zero to the maximum amount intended the current will be controlled by adjusting the effective voltage. At this point the applicable integrals get a bit tedious, but others have reduced the solution to straight math.
What we find is that the effective power, which is what does the work, can be varied in a linear manner by means of pulse width modulation. This is a method that has been used for quite a few years and is well documented and understood. It is not my creation by any means.
The TS has already explained, in post #1, in fact, that that is their preferred means of control. Thus suggesting the means to achieve it with reasonable hardware is valid.
I invite all of the qualified watchers to examine the concepts and details of my suggestion and let me know if I have missed anything.
The one challenge remaining is the high powered DC source for the brake system Unfortunately I do not see any convenient way of achieving the maximum torque load without enough voltage to cause the specified maximum current to flow in each coil. I do see some possible options but they are neither simple nor convenient.

 

There is no inherent "danger" in connecting Coils in Series.
The manufacturer of the Dyno even does it,
every single Transformer manufacturer does it,
and I've done it numerous times.
I've also done it with Speakers, putting 4 in series, with 4-groups of 4,
all on "1" amplifier, and it's performance was excellent, and worked exactly like the Math said it would.

What exactly do You think is going to go "wrong" ?

Smoked ~40-year-old components does not indicate anything except
that the parts are old, and highly stressed, and operating in a crudely designed Circuit.

Transformers seldom, if ever, go bad, unless they've been seriously abused.
The Transformer in question shows no signs of being "cooked".

A brand-new, custom-wound, 240V to 100V, 1200-VA, Toroidal-Transformer is around ~$400.oo,
so it's worth it to figure out a way to use the original Transformer to good advantage.
( And Hammond-Manufacturing recommends using the 2 default Primary-Windings in series by the way )
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So the two of you think multiple 24V relays or contactors can withstand powering the pull in coils with 80V? That would be similar to what your saying here.

First off I don't remember this being one of the Sun Electric dynos in the first place, that was something billy brought into the conversation, not what the TS has, his is home made.

Earlier I posted a link from Telma about their dyno controllers, this particular retarder wasn't listed as compatible. The ones that were compatible also have high voltage coils as replacement parts, from what I have found this, AE30 doesn't only ones for 12V and 24V. The ones that work with the dyno control go up to the hundreds of volts DC.

So lets say for example the 12/24 coils were used at the much higher volts and shorted out, that would in turn take out the control board. reading the actual manual for this AE30 it says NEVER leave the retarder energised when not being turned by the driveshaft of the truck(and as a DIY dyno that's where this one came from) So say someone leaves the thing on while adjusting his car, and the coils overheat and burn out? Which is what the manual was saying, don't leave it on because of overheating the coils. If this was mine the first thing would be to check out the coils in the retarder for shorts.

Just looking at the wire schematic in the link the TS gave if multiple coils can be wired in series why don't they do it? It states in the fine print of the schematic that there needs to be a North and South polarity of the coils and that is designated by a red shrink wrap on the ground wire. Has nothing to do with wiring any other thing you want to suggest. They use one type of coil and put the red sleeve on a different wire when they make one N and the other one S. A matter of logistics and cost saving. Changing the wiring phasing will not let the retarder work correctly, if it did they wouldn't call it out.

I guess what I'm saying is Telas spent money and time to figure this retarder out and make it work to the parameters it was designed for, so why not keep with them and leave them alone?

 

Evidently shortbus does not understand that putting several identical devices in series across a voltage will lead to the voltage developed across each device being a fraction of the total voltage.

 

Evidently shortbus does not understand that putting several identical devices in series across a voltage will lead to the voltage developed across each device being a fraction of the total voltage.

And you assume he has rewired them to work correctly at the higher voltage. I assume he hasn't, since he can't even measure his transformer output. That and his admission to not having any electronics background.

 

One step at a time,
We haven't gotten there just yet.
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I have presumed that the TS is smart enough to have read the same manuals posted here as I did, and also wise enough to have somebody who does have adequate skill and insight look at what changes I have suggested, and ask for additional advice in any areas that I have left unclear.
I have got Personal Messages from folks asking questions a few times, and I respond as needed. The one exception was one individual who wanted a huge amount of engineering for a project that was a very poor concept from it's start.

 

Sorry for the long delay. Have been away.
Where we are at -
I had some additional advice when i got back and have worked out a few things. Basically the transformer, SCRs, Diodes plates are making up a 24vDC 35a scr controlled power supply. Appears the retarder is wired for the 24v configuration and is ample for our requirements.

Have performed a test with a lab power supply with variable current (Set VDC to 24. Set current to 0) connected directly to retarder - and +. Rolled roller by hand and gradually increased current to 5a. Load on roller gradually increased with current.

So now I'm looking for a 1000w 24v Switchmode power supply with variable current based on PWM or some other signal sent by my arduino (Rs232, variable voltage 0-5, usb communication. I can code this).

Or a fixed voltage 1000w power supply with a current limiting circuit thereafter. I'm told I need to be careful with how we restrict the current as a square wave going into the retarder could cause smoke.

Has anyone seen a power supply that would fit this purpose?

 

Scratch that last question. I found one.
1500w Switching Power Supply With Displayer 0-24v 36v 48v 60v 70v 80v 90v 110v 220v 300v 350v Adjustable Dc Voltage& Current - Switching Power Supply - AliExpress
I will remove the A-Adj trim pot and substitute a 5 or 10v (Once measured) analogue voltage.

Hopefully that's problem solved.
Will let you know how I go.

 

Good luck with that supply. One caution is that you should have opto-isolation in the control connection to the computer. And a means to limit the output setting to what your retarder requires. It may even work out better to use a photo-resistive device in place of the control adjustment pot rather than working to interface a voltage for the variable resistance control. That will depend a lot on the control scheme for the power supply.

 

@MisterBill2 Who was right about how it was wired? Still wired as it came from the factory.

 

@MisterBill2 Who was right about how it was wired? Still wired as it came from the factory.

I do not recall offering any guess as to how it might be wired. I did make suggestions about an alternative arrangement of putting all of the coils in series so that the control system would be handling less current and the DC supply would need to supply less current. Those suggestions did not require any awareness of how it had been wired prior to he change.

 

Those suggestions did not require any awareness of how it had been wired prior to he change.

You have a very low retention span of what you say.

 

Hi Everyone,
Looking for some assistance driving an eddycurrent retarder.
My Skills - I have some basic soldering skills and some limited understanding of circuits and their components. Enough to build a timer circuit with Resistor/capacitor and understand basic logic chips jk flipflop ..etc Not enough to build a circuit that uses them. I can write software in many languages.

Essentially I have a very old Dyno for tuning race cars. It has a retarder in it.
This is connected to a slotted disc (12 slots read by optical circuit (Sensor).
This connects to a torsion spring.
This connects to another slotted disc and sensor.
This connects to the roller that the wheels go on.

The current circuit boards used a lot of old chips (1980's) that would measure the rotational speed of 1 disc. It would use the jk flipflop chips to determine the difference in position between the 2 discs. With that information is calculates speed and torque. It feeds a speed signal to a second board that drives the retarder to limit the speed in a desired range.

All the boards are fried so I have purchased an arduino and programmed it. I calculate speed and load based on the input sensors and send a PWM signal output with my desired load for the retarder. This is where I need help -

How do I drive the retarder with my PWM signal? I have approximately 40v coming from the existing transformer. As per the attached pic there is a small circuit board that sends 2 signals to 2 plates (On the left) each plate has
diode and a triac/SCR 2N3898. The SCR connector goes back to the main driver board on the SKA connector. The 2 signals are fed from the 2 resistors just to the right of that and the source of the resistors is the same rail.

So I hope that's enough for someone to understand what's going on. I have purchased one of these in the hopes that it might be what I need. I basically need to know how to take my PWM output from my arduino and drive the retarder through the small circuit board or directly to the plates. I can wire, I can solder. I just can't design the circuit.

Thankyou for any advice. An entire club of race car drivers would sincerely appreciate your help.
BTW we are only driving 1 coil on the retarder.

Also keen to see how this goes. I’ve just recently acquired the same dyno and looking for options to modernise and upgrade.

@Rocketman12

 

I wish you success, a lot of good advice was given to the previous TS. If your intention is to use a computer to control things you will need to first decide how the control scheme will function, because speed and torque are a bit independent from each other.

Then I have the question of just what portions of the original system do you have, and are they able to function as originally intended.?? One choice is to increase the torque load in a linear proportion to speed, another option is to keep the torque load constant as the speed changes, or to hold the speed constant and vary the torque.
And one responder was constantly being very critical as I suggested an alternate arrangement for powering the brake magnets.