RE: [TCML] Are safety gaps necessary? TerryFilter MOVs

["Lau, Gary" <Gary.Lau@xxxxxx>]

For a 12kV NST, I think you may want to remove one MOV per side.

The 1800V figure is certainly misleading.  One really has to read the data sheet carefully, or simply have faith in Terry's original design.

Per Terry's original documentation:
NST     MOV's per side
9kV     6
12kV    7
15kV    8

The spec sheet (http://www.panasonic.com/industrial/components/pdf/awa0000ce2.pdf) gives several parameters for this MOV:
Varistor Voltage (Measuring Current of Varistor Voltage=1.0 mA): 1800V
Maximum Allowable Voltage(RMS): 1000V
Maximum Allowable Voltage(DC): 1465V

Apparently these devices do not have a sharp threshold.  At 1800V it will be conducting 1mA, which is actually a lot, and will cause the device to get hot (1.8Watts, the rated power is only 1.0W) if it did so continuously.  It's the continuous Maximum Allowable voltage one must look at when determining how many to stack.  For a 15kV NST, there's 7.5kV RMS per side, so a stack of 8 will be safe at up to 8kV RMS.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of b alex pettit jr
> Sent: Friday, June 20, 2008 12:41 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: [TCML] Are safety gaps necessary? TerryFilter MOVs
>
> On a related topic,
> How may MOVs are required for safe operation in the
> Terry Filter ?
>
> I have 8 per leg for the 12KV/60ma - just used the
> full set of MOVs provided in the kit, maybe too many ?
>
> Since they are rated at 1800v, 6000/1800 = 3.33
> per side, but seems as if most use many more than that ... ??
>
> Whats the consensus ?
>
> Thanks,
> Alex P
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