Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx> Hi Gerry,Bipolar twins can be run with the secondaries independently grounded, connected together and then run to a single ground, or merely connected together. The latter configuration often results in the best performance. However, as Steve mentioned in his post, the main problem with running ungrounded is often unacceptably high voltage swings that create secondary-primary flashovers. Most coilers simply run with both bases grounded to avoid this problem even though it can reduce performance a bit. Steve's suggestion to run the common base connection to ground through a resistor bank to perhaps get the best of both worlds, and it may also simplify system tuning. Another option might be a safety gap between the common base connection and a solid RF ground.
Bert Tesla list wrote:
Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Bert,This would make sense. When the two bases are connected together, I presume that they are not grounded?? This would be sorta like a bipolar where the center of the secondary is not grounded. Any problems with flashover between secondary and primary in these configurations with no grounded secondary??Gerry ROriginal poster: Bert Hickman <bert.hickman@xxxxxxxxxx> Hi Gerry,I suspect that, since the bases of the twin coils are normally connected together, they should remain synchronized via this connection. When the bottom current is exiting the base of one secondary, a significant portion (or even all of the current if you run with the common base connection ungrounded) will be going into the base of the other resonator. The current flows into and out of the bases should help to keep the coils in sync (~180 degrees out of phase) even after the primary circuit has quenched...Bert Tesla list wrote:Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Steve,I do believe that the primary keeps them in "proper" phase when sufficient energy is still in the primary. My question was addressing what happens once the primary quenches (should be at maximum energy in the secondary). I'm thinking that phase drifting begins at this moment in time if not before. I guess I'm assuming these two coils are side by side and not a bipolar coil. Even with a bipolar coil, if the center turn is grounded, I dont know if the magnetic coupling will keep them properly phased. Maybe Antonio can shed some lite on this.Gerry R.Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx> Gerry, Like you say, the series connected primaries force the secondaries to stay about 180 degrees out of phase with each other and at the same frequency. Once the secondaries have discharged and are ringing down, they probably do exhibit relative phase shift, although there is still some fairly strongelectrostatic coupling between the two top loads until the voltage dies off.But so what if their phase wanders during the last part of their ring-down. The next "bang" from the primary jolts them back into the proper phase to unleash connecting leaders again. --Steve Y.