Re: MOT current

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>

Hi Ted,

> Original poster: tesla <tesla@xxxxxxxxxxxxxxx>
>
> Hi Team, Ted L in NZ here
>
> The question in my view is actually deceptively tricky.
>
> The answer depends on the reactance of the MOT load and of course the size
> of the MOT. Recently appreciated the effect of the effective source
> impedance of a MOT. Due to  the magnetic shunts in the MOT the O/P Z is
> effectively a voltage generator of about 2kV in series with an inductor of
> about 6 Hy and a series resistance (I think of about 200ohms). In an
> experiment some time ago I fed a MOT into a single capacitor (0.33uF) with
a
> static gap across it and measured the peak charging current back into the
> cap when the SG had fired at 3 amps. The peak current will depend very
much
> on the value of the capacitor and the value of the O/P inductance. If the
> value of C is such as to tune out ALL the inductive reactance of the
source
> then the pk current will be maximised. I've test jigged this up and
> certainly the mains current with a short circuit load in series with a
near
> resonant capacitive load goes ballistic.
>
> Because tesla coilers often feed capacitve loads and are interested in how
> much peak current can be fed into the capacitor I believe this type of
> approach to considering the current available from a MOT is more relevant
> than what can be delivered into rms into a resistive load of about
0.5amps.
> The maximum power O/P will be obtained from a conjugate load at 50Hz where
> the resistive component is the same as the MOT source.

Yes but do you want to draw 5A? That's 5kW dissipated in the MOT and 5kW in
the load.
assuming 200ohm and 2kV for the source.
>
> Shortly (after I repair an exploded ASRSG) I intend to try some
experiments
> with a DC resonant charging 4 MOT stack using a series capacitor (another
> MOT cap array) to 'tune out" the effect of the O/P inductance from the MOT
> source. I have found that a bridge rectifier load into a capacitor filter
is
> not a good "match" load compared with a conventional AC tesla. My maximum
> current draw from the MOT's was much reduced to that when running the same
> tesla as an AC excited machine.

Why bother to tune out the L? Just knock the shunts out.
Better yet for AC put extra shunts in where the heater winding was so the
ballasting is a better match to the kVA rating of the MOT. You can then use
a LTR cap without drawing say 5kVA.
>
> Best
> Ted L in NZ
>

Robert (R. A.) Jones
A1 Accounting, Inc., Fl
407 649 6400