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Re: [TCML] The Hammertone Predikter



piranha skrev:
Hi Finn,

I have a question.

As you move the crossover timing from too late to too soon, do you notice that the bridge tends to "lock on" to the correct timing?

When the timing is late, you will have your inductive voltage spikes and all from opening the bridge while current is flowing. You should be able to easily adjust the timing when it is late.

When you reach the perfect timing everything will look fine.

But where it should seem a little odd is if you try to switch the bridge too early. It actually should try not to let you. As you move the timing too early, the IGBTs will almost ignore the timing signal and stay on until the current naturally goes to zero. The IGBT's miller capacitance should try to hold it on. Do you notice that?

I cannot say I have. All I noticed was the voltage waveform forming an upward "dip", I guess telling that no current is being drawn yet. Richie keeps telling me to avoid switching too early, because it will result in current tailing. I am going to look into this, when I get the other big gate transformer core. I am using 2" types for the gate transformer, with 8 strands of wire. 4 of them are seriessed, and fed by a + - 80V square wave gate signal, the secondaries are paralled 2 by 2 , one pair for each brick. so a 4:1 stepdown in voltage. Looks like it has no problem charging the gates, I get the usual looks of signal.

I will probably be able to answer this question thursday evening, when I expect to have the 2nd. core.

You could actually stop the coil's oscillation right there.

By switching it early??

The other IGBT can turn on anytime it wants after that without current spikes or problems.

So it should be that if the crossover timing is a little too early, the thing seems to work very well.

Switching a tad early, is what I have been thinking would be best all the time, and what others have been warning me against.
Going to get interesting to focus on that aspect.


I would be interested if you have noticed anything like this.

Best Regards,

   Terry

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