RE: Bleeder Resistors

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Qndre Qndre" <qndre_encrypt@xxxxxxxxxxx>

Hey Dennis.

1. The resistance is far too low and will waste considerable amounts 
of power. This power will be consumed directly from your LC circuit 
so the oscillation will be damped very quickly. Not a good idea. To 
calculate an adequate resistance value, use the following equation: R 
= t / ( 5 * C ) .. where t is the time you want the capacitor to 
discharge to less than 1% of it's voltage (so if you are throwing 10 
kiloVolts across the cap in use and shut it off in the exact voltage 
peak, it will hold a remaining voltage of less than 100 Volts after 
the time t in seconds). For example if you want your 30 nF capacitor 
to discharge within 5 seconds, you need a resistance of 33 MegOhms.

2. "Hotsticking" as you call it will work for your capacitor. But it 
will not prevent the inner caps of an MMC from floating and still 
holting potential lethal charges. That's why you place a bleeder 
resistor across every single cap in the MMC and not only across the 
outer terminals where you wire it to the tank circuit. Since you are 
not using an MMC I don't see any problem. Just wanted to mention this 
if someone plans to use an MMC.

3. Using a cable to short the outer terminals of the capacitor is 
definitely not wrong since the bleeder resistors may fail (burn, 
break, whatever). Also note that it takes some time to discharge the 
capacitors through the bleeder resistors so they are not safe to 
touch as soon as you shut down the power but will take several 
seconds or maybe a minute depending on capacitor size and value of 
the resistors. Remember the formula you used to calculate your needed resistor.

4. It is recommended to use a bleeder resistor across your PFC cap as 
well in case your NST's primary fails. Note that it is used on the 
low-voltage mains side so you need to calculate the resistor for use 
on mains voltage and not the high-voltage from your power supply transformer.

Regards, Q.

----Original Message Follows----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Bleeder Resistors
Date: Tue, 03 Jan 2006 20:39:11 -0700


Original poster: otmaskin5@xxxxxxx

My wife said don't worry, I don't need bleeder resistors.  But having 
read all your advice on this topic, now I'm a little suspicious of 
her motives.
Thanks for your help.  I do have a couple of other questions...

1.  I have two wire wound power resistors (50W, 1KOhms) not being used.
Would one or both of these make a suitable bleeder resistor for my 
.03uF 35,000v Maxwell cap?

2. I'm hearing, even with bleeder resistors, hot sticking to 
discharge the cap is still adviseable.  I have been holding a stiff 
wire (taped to a length of PVC) accross the Maxwell's 2 terminals for 
5 or 6 seconds.  Is that sufficient discharge procedure?

3. One of the responses also recommended "locking it out."  Can 
someone explain what this means?

4. I also have PFC caps on my coil.  I assume these also need to be 
discharged?  Same procedure as with tank caps, right?  Would you use 
bleeder resistors on PFC (motor run) caps?

Thx, Dennis Hopkinton, MA