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Forum Index : Electronics : Bleeder Resistors Question
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WindyMiller Regular Member  Joined: 05/04/2011 Location: United StatesPosts: 62 |
GidDay Everyone! I have what must seem like a dumb question from someone who actually knows a great deal about electric generation? Anyway my question is this? For a while I have been dumb founded as to how one knows how to calculate a proper bleeder resistor for a 10 UF oil cap? I have been told I need the following 10 Ohm 5 watt 15 Ohm 2 watt 100 Ohm 2 Watt 7.5 Megaohm My circuit is 120 Volts AC 60Hz 20 amps. the cap is connected across the positive and netural wires between the generator and the outlets. How do I calculate a proper bleeder that will drain my caps quickly but not constantly dissapate 10 watts or so of power to ground which will waste alot of power in my new design. The design is a twist on the induction machine. I was told by someone else that a 1 Megaohm resistor would dissapate a few milliwatts which is what I am looking for if it would work? I have 98 1.6 Megaohm resistors rated for 200 volts atleast. I would like to use one of these since I have them. I would normally just try all of the above, but do to time constraints I am looking for a quicker answer or more of a definite answer if one exist. PS. Sorry for the bad english. It is after midnight and I am beat. Robert |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Robert. How quickly is quickly? You can work out how quickly a resistor will discharge a capacitor using some RC maths http://en.wikipedia.org/wiki/RC_circuit. A 100k 1/2 watt resistor would do. Its only going to be dissapating 0.15 watts, and would discharge a 10uF cap to a save voltage in a couple of seconds. Is it just a safety issue? Making the cap safe to work around once power is removed? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| WindyMiller Regular Member Joined: 05/04/2011 Location: United StatesPosts: 62 |
Glenn, The circuit is switchable between two different modes and if there is a charge in the cap it could damage parts in the other half of the ciruit. I need the cap to completely drain in a matter of seconds. Just enough time to stop the engine and throw the switch and then restart the engine. Do to the amperes the switchover has to be made with the unit stopped to stop from arcing the contacts in the switch and feeding a potentially high voltage spike into a solid state circuit. I also want all of the caps to drain when the machine is stopped for the day. The unit has a excitation circuit and does not need the residual magnetism. Robert |
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MrDelanco Senior Member  Joined: 12/11/2011 Location: United StatesPosts: 101 |
Redesigning the circuit and adding a subsystem too discharge the charge. Show us the circuit design you are working with. Cheers Robert. MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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| WindyMiller Regular Member Joined: 05/04/2011 Location: United StatesPosts: 62 |
The circuit is nothing more than a solid state power supply like that from a computer. I am using one of those battery chargers that is solid state as a transformer type would not work on a induction machine. The generator is being built to supply a set of recepticles or a large battery charging circuit. I will try and draw up a schematic or find something close to it as an illustration of the battery charger. As for the bleeder resistor I figure I need a setup that can bleed the caps in 5 seconds or less and yet not present a significent drain as it would mess up the preformance of the induction machine. Under 1 watt of constant drain is what I am looking for. Not the massive 10 watts that was suggested by someone else to me locally. Robert |
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