I'm going to make a bleeder wire resistor with a 12k ohm 2W resistor to bleed some electrolytic capacitors.
Firstly, a guide I found said to use 12AWG wire for this. Is there any need for it to be 12AWG as although the voltages could be 450V+, the current is likely to be very small.
Secondly, is there any minimum voltage of small capacitors non electrolytic that it is not necessary to bleed them? There are many in a circuit.
Firstly, a guide I found said to use 12AWG wire for this. Is there any need for it to be 12AWG as although the voltages could be 450V+, the current is likely to be very small.
Secondly, is there any minimum voltage of small capacitors non electrolytic that it is not necessary to bleed them? There are many in a circuit.
I use a length of flex with crocodile clips on the ends to bleed large electrolytics. The resistor varies with the capacity and voltage. For say 100uF 450V I use 120k 1/2 W, 10,000uF 100V 10k 2W. I have a selection including a 15W 240V pygmy lamp.
12 AWG is vast overkill. 24 gauge would do the job. Yes, use wire with at least 600 volt or better insulation. Common hookup wire is often only good for 300 volt.
Hard to say as a perfect generality. The usual goal of bleeding is personnel and equipment safety, not some arbitrary voltage.
But how? The voltage can't pass through the outer sheath?!
And is it an immediate shock hazard or only after a period of time?
For example, alligator clips have a cover that is probably nowhere near 600V
Never use insulation that is under-rated for the application.
If not specified, assume the insulation is only good for 50V, including the boots on alligator clips.
In general, never connect/disconnect test leads while a circuit is powered.
I won;t but I'm interested in what would happen?
I don;t understand how voltage could "jump" across the insulation or damage it. Only current would overheat the insulation.
Well, you don't know what might happen, that's the point. Only 50V is enough to kill you in the right (wrong) circumstances,
because of current through the heart. Or, a spark that startles you and causes an accident.
https://en.wikipedia.org/wiki/Insulator_(electricity)
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The alligator clips with a flexible insulation, are those 600V rated or must they be much thicker?
What do you generally use for electronics?
If it isn't marked with a voltage rating, assume 50V. Rubber is better and more durable than PVC.
Use wire (in good condition) that is marked with a voltage rating less than the voltage actually present in the circuit.
If the insulation has been damaged, cut, or melted, discard that part. I use 600V wire for circuits less than 450V.
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Hmm. Cannot find any 600V rated alligator clips in the hardware store...
Car parts store maybe?
Maybe then you shouldn't use them. If this is for a DVM, the test leads that came with it should be of adequate rating
for any voltage that the meter can read. I agree that probing circuits can be tricky, but you must do it in a safe manner.
There's the strange thing. The meter is rated for 500V.
The insulation on the leads is at leats the same thickness or even less as that of 12AWG NMD90 cable, which is only 300V rated.
Not a bad idea though, I could get a spare set of DVM cables and solder in the resistor to the connector that normally plugs into the DVM, then put heatshrink around that.
Maybe new leads would be best, at least for high voltages. Or, get some "test probe wire" which is usually rated at 1kV and higher.
Shrink tubing has a similar voltage rating problem, though.
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