I'm not getting this. Why are all three taps shorted together at the output ?
The second two have both ends shorted together. What is the point of that ?
raschemmel:
I'm not getting this. Why are all three taps shorted together at the output ?
The second two have both ends shorted together. What is the point of that ?
Perhaps to demonstrate that even inductors are capable of outputting the magic smoke when you shorten together their turns
Whatever form of switch is used it must be "break-before-make" and as has already been suggested, relays really are the way to go
raschemmel:
I'm not getting this. Why are all three taps shorted together at the output ?
The second two have both ends shorted together. What is the point of that ?
It's badly drawn
Only one box is on at a time
jackrae:
Perhaps to demonstrate that even inductors are capable of outputting the magic smoke when you shorten together their turns
Whatever form of switch is used it must be "break-before-make" and as has already been suggested, relays really are the way to go
Current method uses large lumps of iron and copper.
Also working voltage will be 10 X 40 v and large expensive caps are also required.
If i used relays which would be expensive to get a useful life they would need to be mercury whetted.
Main point of the exercise is to get weight and cost down.
fabelizer:
You could switch with properly rated and properly protected FETs. (flyback diodes, snubber networks)
So, what is the problem you are trying to solve?
Need a variable voltage that is electronically selectable?
This thingamabob puts out 40Vac and I need to reduce it to read different scales?
What?
-fab
Its a psu smoothing circuit.
It's being fed from an IMAG generator and I cannot use capacitive filtering as it kills the excitation current.
In one variant (wind) the input will be varying frequency (and voltage )and the circuit becomes very inefficient hence the desire to switch inductors.
Last time I looked at this it was unfeasibly expensive but I think that using an arduino its do able now
Then use heavy duty relays (aka contactors) with suitably rated contacts for DC. 10amps is chicken feed. You are looking for problems where they really don't exist.
Boardburner2:
It's being fed from an IMAG generator and I cannot use capacitive filtering as it kills the excitation current.
In one variant (wind) the input will be varying frequency (and voltage )and the circuit becomes very inefficient hence the desire to switch inductors.
It took (just) a little research to figure out what on earth you were talking about.
I think you need to justify the part about "becoming very inefficient". In general, a choke input filter should be just fine with the maximum inductance, so please explain that. (Back to the XY problem.)
Clearly, the usual way to approach this is to rectify the generator output and feed it to a switchmode converter to deliver the desired output voltage I am not quite sure how you optimise the generator V/I curve however - is this what you are looking at?
Boardburner2:
All this mention of relays makes me think that folks around here are thinking that the op should stop playing with matches and go boil an egg.
No idea where to find one these days as transformer kits have disappeared.
20H ??!!! That could be storing up to 1000 joules, so any naive switching scheme will
be toast. You need some sort of path for the 10A at all times or you'll cause
an explosion - that's enough stored energy to vaporize a relay's entire contacts I think.
However you've probably got 10's of volts AC between taps - perhaps massive MOV
or TVS diodes across each relay/MOSFET? They will have to take 100's of watts
during switchover, so MOSFET wins for that by fast switching time.
jackrae:
Perhaps to demonstrate that even inductors are capable of outputting the magic smoke when you shorten together their turns
Whatever form of switch is used it must be "break-before-make" and as has already been suggested, relays really are the way to go
Explode before make with a 20H load I should think!
Seriously this size of inductor is extremely dangerous if mishanded, any kind of interruption
of 10A through 20H could lead to voltages far beyond what mains-rated components
can stand and at instantly lethal currents.