[Amps] SAFETY WITH HIGH VOLTAGE

[DF3KV]

----- Original Message -----
From: "Harold B. Mandel" <ka1xo at juno.com>

> To answer some of the questions:
>
> A beehive is a porcelain assembly that serves to insulate high
voltage as
> it
> feeds through a chassis wall.  Sometimes bigger beehive insulators
> are used to run antenna transmission feedlines through walls.
>
> The bleeder resistor network is (or now, was) composed of four
> pieces, 100K ohms, 50 watt vitreous enamel OHMITE L50J100K
> less than 12 months old, less than 1 hour operation. The resistors
> were megged with a DMM before assembly into the plant.
>
> When examined today, one piece was infinite resistance.
> A second piece is now 29.2 meg. The third resistor is 110K,
> and the fourth, get this: 53.2 ohms.
>
> It sounds to me like there was something of a domino effect.
> However, at the actual HV level of 3804 volts, is nine and
> one-half mils. This is thirty six watts. Fifty watt resistors
> should have handled it, especially mounted with spring clips
> in an airflow. If one resistor shorted to 53.2 ohms, the
> network then was then 12.6 mils. This would have brought
> the dissipation to 48.2 watts. There's a hefty airflow, remember,
> so that may or may not have been the trigger for the
> other devices to fail.
>
> Comments???

Hi Harold,

Most resistors are specified for only 500V, so unless you use special
hv resistors you need at least 8, better 10 resistors serial connected
to form the bleeder bank.

73
Peter