Selection of a transformer
Plasma, Thu Aug 03 2017, 06:51AMHi I've got a 4ms pulse at 15volt which I'm feeding a lead acid battery, through a transformer, and I'm simulation the battery by a 13volt zener and a 0.1ohm reisistor.
The question is what physical trans to select, the pulse is 3amp,at 13-20volt.
Thanks
Re: Selection of a transformer
Dr. Slack, Thu Aug 03 2017, 04:50PM
Ferrite? I'm not certain I understand exactly what you're asking.
Dr. Slack, Thu Aug 03 2017, 04:50PM
Ferrite? I'm not certain I understand exactly what you're asking.
Re: Selection of a transformer
Plasma, Thu Aug 03 2017, 07:07PM
The pulse is 4ms wide, and happens every 200ms,it is about 3amp,with a voltage of 15-20volt.
What type of transformer to use, ferrite or steel.
The simulation works at 100mH prim/sec
Does the wire gauge need to have a size for 3amp continues.
It will be a pulsed dc, will that effect much.
Cheers
Plasma, Thu Aug 03 2017, 07:07PM
The pulse is 4ms wide, and happens every 200ms,it is about 3amp,with a voltage of 15-20volt.
What type of transformer to use, ferrite or steel.
The simulation works at 100mH prim/sec
Does the wire gauge need to have a size for 3amp continues.
It will be a pulsed dc, will that effect much.
Cheers
Re: Selection of a transformer
Dr. Slack, Fri Aug 04 2017, 08:53AM
There are several limitations on wire. You have to go with whichever bites first, whichever is the most restrictive. There's heating, for which you use RMS current. 3A/mm2 is a rule of thumb for small transformers, though if it's sparsely wound (that is, well cooled) you can go above that a bit. There's voltage drop, for which you use current and resistance, and will depend on your application. Then there's output impedance, where the resistance gets added to your leakage inductance, which also depends on your applciation.
At 4mS, you're probably talking about ferrite, even if the frequency of the pulse train looks to be within the realms of iron. It's more the risetime of the pulse (which you haven't specified yet) that will explore the differences between steel and ferrite.
The pulse length requires a certain area of core, you can't exceed its volt.seconds product, if you do it saturates.
Note that a uni-directional pulse has a DC component. A train of those pulses will saturate a transformer, unless you do something to reset the flux between pulses. AC coupling the pulses into it with a capacitor works, but you may find that distorts the pulses more than you want. If it does, then you may have to do something more complicated, or rethink entirely.
Dr. Slack, Fri Aug 04 2017, 08:53AM
There are several limitations on wire. You have to go with whichever bites first, whichever is the most restrictive. There's heating, for which you use RMS current. 3A/mm2 is a rule of thumb for small transformers, though if it's sparsely wound (that is, well cooled) you can go above that a bit. There's voltage drop, for which you use current and resistance, and will depend on your application. Then there's output impedance, where the resistance gets added to your leakage inductance, which also depends on your applciation.
At 4mS, you're probably talking about ferrite, even if the frequency of the pulse train looks to be within the realms of iron. It's more the risetime of the pulse (which you haven't specified yet) that will explore the differences between steel and ferrite.
The pulse length requires a certain area of core, you can't exceed its volt.seconds product, if you do it saturates.
Note that a uni-directional pulse has a DC component. A train of those pulses will saturate a transformer, unless you do something to reset the flux between pulses. AC coupling the pulses into it with a capacitor works, but you may find that distorts the pulses more than you want. If it does, then you may have to do something more complicated, or rethink entirely.
Re: Selection of a transformer
Blackcurrant, Fri Aug 04 2017, 08:44PM
try looking here it'll give you some ideas also wire size needed etc
do you really need a transformer though as anything above 13v may charge it up?
Blackcurrant, Fri Aug 04 2017, 08:44PM
try looking here it'll give you some ideas also wire size needed etc
do you really need a transformer though as anything above 13v may charge it up?
Re: Selection of a transformer
Plasma, Fri Aug 04 2017, 10:29PM
It's not a transformer persay, but it can isolated two networks, if I have two of the circuit charging the battery, the capacitor discharge at the same time. I'm not sure how to do it, except with a circuit control the discharge of the two circuit at different times.
Plasma, Fri Aug 04 2017, 10:29PM
It's not a transformer persay, but it can isolated two networks, if I have two of the circuit charging the battery, the capacitor discharge at the same time. I'm not sure how to do it, except with a circuit control the discharge of the two circuit at different times.
Re: Selection of a transformer
Dr. Slack, Sat Aug 05 2017, 04:29AM
If it's *not* a transformer, per se or not, then a different design process might apply. What is it? Add a schematic, or a photograph, or a link. Your OP seemed to suggest it was a transformer, in the physical sense.
Dr. Slack, Sat Aug 05 2017, 04:29AM
If it's *not* a transformer, per se or not, then a different design process might apply. What is it? Add a schematic, or a photograph, or a link. Your OP seemed to suggest it was a transformer, in the physical sense.
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