Do you mean a brief surge, which then goes back to zero?
If so, that's from the capacitors charging, and is normal.
If so, that's from the capacitors charging, and is normal.
I will try it, but I would think nothing, since neither chokes go to ground. If they were somehow shorted already, would they not just get warm (at full voltage)? the caps are polyprop. and do not have a pos/neg per se; so having "chosen" their pos/neg orientation, it is unlikley that any of them are put in incorrectly.
I will let you know about shorting the chokes.
Thanks
I will let you know about shorting the chokes.
Thanks
Allow me be clear with your answer: Are you suggesting that the ac comes in from the wall and then goes into into the variac first or to the transformer first?
Variac connects to nominal mains Vac. Depending on the variac's range of output, the following transformer can be energised with Vac ranging from at or near 0Vac, to at or just above mains level Vac.
The mains AC feed will experience an in-rush current when connecting to the variac, which could be significant if the variac has a high power capability, as the variac core is typically a toroid. I use a 300VA variac, which covers all my benchtop test requirements.
I also use a plug-in cheapo digital power meter with the mains input to the variac, as it tells me nominal mains voltage and mains current (which includes a contribution from the variac itself, which I then subtract from the current level when the DUT is connected). The variac dial indicates nominal Vac presented to the DUT/transformer, which I only need to generally know, as I am more concerned with what the current level would be going into a device/transformer.
The mains AC feed will experience an in-rush current when connecting to the variac, which could be significant if the variac has a high power capability, as the variac core is typically a toroid. I use a 300VA variac, which covers all my benchtop test requirements.
I also use a plug-in cheapo digital power meter with the mains input to the variac, as it tells me nominal mains voltage and mains current (which includes a contribution from the variac itself, which I then subtract from the current level when the DUT is connected). The variac dial indicates nominal Vac presented to the DUT/transformer, which I only need to generally know, as I am more concerned with what the current level would be going into a device/transformer.
Thanks. I asked because when I wired it up that way, I don't seem to get much of a transformation from the ac to the dc output even though there is a significant transformer between the ac mains and the recitfier: 750-0-750. (Mind you, I don't turn up the variac all the way out of concern that it will short somewhere). Is there a threshold point where the transformer has to reach a "critical inductance" in order to show its true output voltage? I even checked the a/c going in and out of the transformer and found that there was not much in the way of a transformation. This btw, is using the variac at 1/2 voltage.
Perhaps start with an accurate schematic sketch of the parts you have connected, as your first 'schematic' showed a low voltage power supply, but now you are referring to 750-0-750. You are also making measurements on high voltage levels, so the meter, and your experience, and aspects of safety are all concerns.
If the transformer secondaries are all unloaded, then the Vac of a secondary should be pro-rata voltage to its rating as the variac output is raised to its mains Vac output level. That assumes the transformer is ok, an there are no connection or measurement errors. If you are feeding the transformer with 50% of mains level, then the 750-0-750 winding should measure at about 375-0-375Vac. Do you get that response for starters?
Are you able to measure the mains current, as that should only rise to a fairly low level with the variac only on, and then similarly shouldn't rise to too much more with the transformer connected (and no secondary loading).
Perhaps when that is sorted then the topic of chokes, and regulation, can be elaborated on imho.
If the transformer secondaries are all unloaded, then the Vac of a secondary should be pro-rata voltage to its rating as the variac output is raised to its mains Vac output level. That assumes the transformer is ok, an there are no connection or measurement errors. If you are feeding the transformer with 50% of mains level, then the 750-0-750 winding should measure at about 375-0-375Vac. Do you get that response for starters?
Are you able to measure the mains current, as that should only rise to a fairly low level with the variac only on, and then similarly shouldn't rise to too much more with the transformer connected (and no secondary loading).
Perhaps when that is sorted then the topic of chokes, and regulation, can be elaborated on imho.
More info please!
- Variac power rating and adjustable range
- Transformer power rating and input/output voltage
- Rectifier voltage rating, bridge or 4 diode?
- Filtering capacitors capacitance and voltage rating
- Choke inductance and current rating
What is the current consumption and how you measure it? Is it possible that one or more capacitors are shorted internally?
