Don,
I use an ignition transformer for a fuel oil furnace to test breakdown
voltages. These are 120VAC primary and a grounded center tapped
secondary of 6kVAC to 12kVAC. They are readily available, are impedance
protected and made by companies such as LaFrance and Dongan. The model
I have is a Dongan LJH-90A and it has a secondary of 5000VAC-GND-5000VAC
(14kV peak across the entire secondary) and the maximum current it
produces is 23mA AC rms. The output can be shorted indefinitely (which
could happen if the igniter in the furnace was clogged). I use a 3A
variac to power the primary and use some Caddock MX440 5meg ohm
resistors in series with the secondary. These resistors are good for
11kV across them and limit the current to sub-milliamp levels.
I generally limit the current via the resistors and when testing and a
breakdown doesn't cause damage to switch contacts, relay contacts, air
variable capacitors etc. If possible I only use one side of the
secondary and place a multimeter in series with the center tapped lead
(multimeter at ground potential) and can watch the leakage that occurs
prior to a breakdown.
Concerning the breakdown voltage at HF vs 60Hz I have a pdf document
showing a fairly good correlation between testing at HF and at 60Hz. If
you want the document I can send it to you.
73,
Larry, W0QE
On 11/25/2010 7:49 PM, donroden@hiwaay.net wrote:
> Has anyone used neon transformers to build an insulation tester ( Megger ).
>
> I need something to go to around 10KV for testing capacitors ( type 291 )
> under a high voltage /low current condition.
>
> Don W4DNR
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