hello,
I plan to make an AC testing supply for the bench. Idea is to have some tools in a box :
- line filter,
- galvanic isolation,
- switch neutral to earth
- differential switch
- power/volt meter
- variable or step limiting fuse
- variable voltage not requested but if possible
there are tons of solutions ! At first sight, a Shaffner two stages filter, an isolation transformer with screen, a combi power volt meter and a differential switch on DIN rail... for variable short-circuit may be a selector with differents automatic thermal fuses....
Tell me please if you have another way to answer the need.
Have a nice day.
I plan to make an AC testing supply for the bench. Idea is to have some tools in a box :
- line filter,
- galvanic isolation,
- switch neutral to earth
- differential switch
- power/volt meter
- variable or step limiting fuse
- variable voltage not requested but if possible
there are tons of solutions ! At first sight, a Shaffner two stages filter, an isolation transformer with screen, a combi power volt meter and a differential switch on DIN rail... for variable short-circuit may be a selector with differents automatic thermal fuses....
Tell me please if you have another way to answer the need.
Have a nice day.
It would help if you could discuss what you are trying to accomplish. Fuses will limit current in the sub-cycle range under fault conditions. I am guessing this is not the current limitation scope you are interested in. The application for swapping in different fuses in this manner would be to limit the energy provided to a failed circuit, reducing arc flash hazard and risk of fire.
Another application of current limitation would be the intentional addition of impedance to limit the current available on a continuous basis. This is not done with fuses. Your isolation transformer will do a good job adding in some impedance. If you want further options for reducing available current (not sure why you would) then you would use additional reactors or resistors in series with the source supply.
What is the intent?
Another application of current limitation would be the intentional addition of impedance to limit the current available on a continuous basis. This is not done with fuses. Your isolation transformer will do a good job adding in some impedance. If you want further options for reducing available current (not sure why you would) then you would use additional reactors or resistors in series with the source supply.
What is the intent?
Further to zigzagflux, I recommend you also outline if your vision for testing is just focussing on steady-state power/voltage measurements.
hi friends,
in a few words, I would like a kind of clean power (without usual spikes or others noise from house) with selectable short-circuit limiting (not house 16A breakers);
Madam also appreciate to not be in the dark when a differential fault occurs during my hobby 😎
in a few words, I would like a kind of clean power (without usual spikes or others noise from house) with selectable short-circuit limiting (not house 16A breakers);
Madam also appreciate to not be in the dark when a differential fault occurs during my hobby 😎
You are looking for a coordinated system, where the fuse is guaranteed to blow before the panel breaker?
If so, the optimal solution is to plot out their time-current curves on top of one another, and see if there is overlap. Overlap implies the possibility for miscoordination, where the breaker could trip simultaneously with the fuse clearing time.
Practically, you will find the fuse tends to open very fast, and the breaker does not trip on instantaneous. However, depending on the speed/shape of the fuse, you could miscoordinate in the overload region.
If you can provide actual manufacturer/catalog numbers, I might have the models in my library to plot them out. Otherwise, just select a fuse 25%-50% of the upstream breaker and consider it 'good enough'.
If so, the optimal solution is to plot out their time-current curves on top of one another, and see if there is overlap. Overlap implies the possibility for miscoordination, where the breaker could trip simultaneously with the fuse clearing time.
Practically, you will find the fuse tends to open very fast, and the breaker does not trip on instantaneous. However, depending on the speed/shape of the fuse, you could miscoordinate in the overload region.
If you can provide actual manufacturer/catalog numbers, I might have the models in my library to plot them out. Otherwise, just select a fuse 25%-50% of the upstream breaker and consider it 'good enough'.
Last edited:
My setup is a 48Vdc battery bank running a very high quality 240volt 5kW (12kW peak) pure sine-wave inverter*, then surge protected power outlet, then 1:1 isolating transformer with 2A breaker giving balanced floating mains, followed by Variac with output voltage and current meters, followed by switchable dim bulb setup, followed by the device under test.
The dim bulb setup has two bulbs, one is 60W, the other one is 100W switchable, giving 160W in parrallel, plus for convenience there is a switch to bypass the bulbs. 160W dim bulb is still a little small for working on most class A amplifiers, so I am looking for a 150W or 200W bulb for the big one, but they are hard to come buy now everything has gone LED for domestic lighting.
*My place is off-grid solar powered; a large high quality UPS is another option to get off the dodgy municipal electricity supply.
The dim bulb setup has two bulbs, one is 60W, the other one is 100W switchable, giving 160W in parrallel, plus for convenience there is a switch to bypass the bulbs. 160W dim bulb is still a little small for working on most class A amplifiers, so I am looking for a 150W or 200W bulb for the big one, but they are hard to come buy now everything has gone LED for domestic lighting.
*My place is off-grid solar powered; a large high quality UPS is another option to get off the dodgy municipal electricity supply.
Last edited:
My thoughts followed a similar path, and I ended up with this:
Here is my new E-baby:
It does not provide a galvanic isolation, but part of my lab supply is fed by a ~3kVA low-capacitance isolation transformer having primary and secondary screens, and I have added a substantial EMI filter.
I don't recommend building this thing though: the basic idea is excellent, but the MOS drivers are a nightmare: they need an extreme accuracy combined with a tear-drawing CMRR level.
If you are not looking for such extreme performances, there are probably easier ways to get a simili-AC lab supply, using a regular variac combined with a MOS controlled ballast inside a rectifier bridge.
I think that ~40 years ago, Elektor described something similar, except all the electronics were safely behind a low-voltage transformer.
Nowadays, direct mains operation is possible with suitable MOSfets (but you have to be extra-careful, obviously)
OP, would you mind describing the AC mains system you presently have to your hobby 'bench'? Eg. do you have a protective earth mains distribution with active and neutral wiring from a switchboard, and what protection devices are at the switchboard and at your bench that you then connect to and through?
Can you also describe a typical project where you believe you need to change the standard mains AC interface from one which provides a protective earth connection along with shrouded and insulated mains circuitry and using parts that are compliant with standard mains level operation.
Can you also describe a typical project where you believe you need to change the standard mains AC interface from one which provides a protective earth connection along with shrouded and insulated mains circuitry and using parts that are compliant with standard mains level operation.