[modeleng] Re: Electric Traction Problems

Hi Peter,
    I went down this road a couple of years ago, powering my 1 HP 24 Volt 
Motor for the Diesel Outline 7.25 gauge. and at the end of the day I decided 
to go commercial, using a controller made by Parkside Electronics of Nelson 
Lancs. this gives me regen breaking and has been in regular use passenger 
hauling for two seasons. It works well and has not given me any problems. 
However 90 amps is rather a lot to draw at 12 volts, although at 24 volts it 
would be almost half that current. The cost of the parts is quite expensive 
and at the end of the day I was happy to not reinvent the wheel and use a 
commercial product.
Parkside specialise in Electronic Control Gear and I can recommend them. 
(usual disclaimer). Brian Howorth is the man to talk to if you go down that 
route.
Best wishes
Don.
----- Original Message ----- 
From: "Patrick Coppens-Marian Lynch" <develop@xxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Friday, April 06, 2007 4:45 PM
Subject: [modeleng] Re: Electric Traction Problems


Peter,
90 amps, or 90 milli-amps
The priciple is the same. Yes, you need to get into some industrial
power electronics,if need be, you have to do some parallel switching of
power components, and indeed you need more than a little multi meter,
bought for 10£
As far as your remarks go about the 'TO 220" plastic devices, you are
correct, but i am thinking of a 'SOT 227 package' that cost 20£,
switches 200 amps, can stand 600 volts over the junction (i forget the
type N°...)
And of course you will have to do some serious 'heat-sinking', but the
control circuit can be mounted on a PCB. If an optical way of coupling
the power circuit to the control unit is used, you will not have to
replace the controls but just the power transistor/triac/thyristors if
the give way...
90 amps on 12 Volts is just under 1100 watts so this should be possible...
Patrick
peter.chadwick@xxxxxxxxxxx wrote:

>Patrick said:
>
>
>>If they are, these are quit easy to make your self.
>>
>>
>If you give me the specs, the system they use (pulse I supose...) and
>some time, I will make you a circuit diagram.<
>
>At 90 or more amps, I'm not quite so sanguine about that. For lower
>currents, yes, but anything above 10 to 20 amps isn't quite that easy.
>Certainly wouldn't be printed circuit board stuff, although the drive for
>the switches would be. The other problem is that you'd need more than just
>a multi-meter to trouble shoot it. I must admit my experience with PWM on
>small DC motors was rather disappointing - and I do have a LOT of test
>gear! The switching devices are going to be something, too - you won't
>switch 90 amps with a plastic TO220 device!
>
>Real electronic devices use valves and glow in the dark. Anything else is
>best done with steam and mechanical stuff!!! Although for my work, it
>would be difficult - can you imagine how you would make a steam powered
>heart pacemaker?
>
>Peter Chadwick
>Swindon
>
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