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Re: [TCML] MOT Measurements



Hi Team

Couple of observations.

I agree in a standard AC design MOT resonance due impact of magnetic shunts generating leakage inductance is not an issue relating to resonating with the Tesla primary cap unless it is really really big. However in a DC system where MOT's are rectified and MOT's "see" filter capacitances or where secondary side capacitive ballasting is being incorporated all bets are off and the impact of the significant inductance needs to be considered (about 6Hy per MOT at operating currents and with primary side shorted which is equivalent cct when feed by mains). Worth noting in many stacked designs the MOT leakage inductances are all in series resulting in an even larger inductance thru which the equivalent voltage generator is required to "see" the load..


I've found it very difficult to get power out of a MOT (real grunt) unless they see a conjugate impedance (at least a moderatly capacitive load) and specifically designs requiring short pulses to charge the filter caps at the peak of the cycle have been unsuccessful for me. I interpret the situation as being one where getting short current pulses "thru" the leakage inductance simply results in the large reactance of that inductance limiting the charging current not to mention the high required currents thru the diodes and in and out of the filter caps)

The exception being the design (scopeboy et al) where the MOT is AC coupled to +ve and -ve peak clamps to generate 2 x pp which works well because those designs do provide a correct value capacitive component in the load seen by the MOT.

For those who may have interests I have looked quite closely at the impact on Secondary inductance in MOT's of DC in the winding for DC inductive charging use. (They saturate really quickly and must be gapped s if this is to be avoided and even then getting large L and high current capability is a real balance)

Best
Ted in NZ

----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, December 31, 2008 2:08 PM
Subject: [TCML] MOT Measurements



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