Behaviours of a transformer questions.

[Nali2001]

Hi Tim,
How exactly did you determine the efficiency?
And you say:
"I've ordered a variable power supply [0-30v,0-5A] to power the DC transformer shown in the picture above. To be able to take Amp reading from the secondary coil I need some kind of load"

I also then presume you have a pulsing circuit to pulse the coils? I mean how do you intend to measure the output of the secondary with steady dc?
And you absolutely need a scope with a current shunt if you want to know what is going on with dc pulses. Since pulses work with duty cycles and are not 'on' all the time you need devices that take these into account. And a digital or analogue meter will not show good results. See it this way:
watt is volt times amp right? But that is only so in a dc situation. Now if you were to drive a transformer/motor/whatever at 100v dc, and pulse it with 100amps BUT with only a duty cycle of say 10% your meter will probably say something like 100v(or less) and about 75amp, So 7500 watt. But that is bogus. it is more like (100voltx100amps) / 10duty= 1000watt
You can only truly determine these ratios with a scope. Also look up 'Rms' or 'true Rms'

[nwman]

How exactly did you determine the efficiency?

I used a digital multimeter with a max setting to read both the input and output Volts and Amps. I used both a small DC motor and small light bulbs as the load and had both two AA batteries in searies and a 9v. So its not a full proof testing situation and my numbers may be flawed but on most occasions it averaged out to 75%+/- .

I also then presume you have a pulsing circuit to pulse the coils? I mean how do you intend to measure the output of the secondary with steady dc?

Again, not too perfect but I just used a push button switch to pulse the coil by hand. It seems to give fairly consistent readings besides the drain of the batteries. Is there any simple product I could buy that would just keep a constant pulse at the varying V and A?


And you absolutely need a scope with a current shunt if you want to know what is going on with dc pulses. Since pulses work with duty cycles and are not 'on' all the time you need devices that take these into account. And a digital or analogue meter will not show good results. See it this way:
watt is volt times amp right? But that is only so in a dc situation. Now if you were to drive a transformer/motor/whatever at 100v dc, and pulse it with 100amps BUT with only a duty cycle of say 10% your meter will probably say something like 100v(or less) and about 75amp, So 7500 watt. But that is bogus. it is more like (100voltx100amps) / 10duty= 1000watt
You can only truly determine these ratios with a scope. Also look up 'Rms' or 'true Rms'

I'll look into this. I may need to buy a scope but for now I'm taking you advice and taking small steps. Would you have any recommendations on a scope? I have seen people show reading from that look like a software based scope. Is this expensive to  buy?

For now I just want to see a crude test of pulse in and pulse out and see what happens. Input is welcomed.

Tim

[Nali2001]

Hi Tim,
First of all, I know I often sound somewhat direct and such in my answers but I mean no 'harm'
Nice to finally see someone diving into the vast field.

Some answers:
Your meters in this test are more or less useless especially the digital once, analogue would be better but still not all that useful. Any experimenter needs a scope. This makes it all much more clear and makes ya pulses visible as well. But it is a learning curve on it's own so just to remind you that this field is vast, even the basics. But coming back to the scope, there are a lot of second hand scopes on ebay and such. These are often oldish analogue scopes which do not much more than just show the curve and thats it. Now for a few more dollars you can get yourself a hand usb scope that comes with software http://blog.cc-robotics.de/wp-content/uploads/2008/02/dso2090_1.jpg that lets analyze and measure on the fly what your curve is doing. It can also calculate rms valves for easy calculation of wattages. I guess I would recommend the dso-2090,  http://cgi.ebay.com/New-DSO-2090-100Msa-s-USB-PC-Digital-Oscilloscope_W0QQitemZ300263917184QQihZ020QQcategoryZ104247QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
It comes with two probes as well. http://www.partsforhdtv.com/images/tools/dso-2090_02.jpg

Well about the pulsing. It more or less depends on a few things I could send you a circuit digram which will show ya how to build a fet based pulsing system. Or maybe a relay, although don't expect them to last long at such speeds... http://en.wikipedia.org/wiki/Relay

You are right and take the small steps so that they are understandable. That way you have something to show for in the long run.