Body
Hi Sven,
Reconsideration
The small thyristor (SCR) can be used as a non-variable triggering device that trig at its breakdown voltage if the cathode is connected to the gate of the main SCR. The anode is then fed through the current limiting resistor to the opposite side of the capacitor for monitoring the voltage across the capacitor. Perhaps it even can be made variable by some resistor voltage dividing network like shown here if the pasting gets through:
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hello Ole, you're right the series resistor only limits the current not the voltage. I'll probably stay with the 1200v thyristors. The thyristors in the pdf consume 60% less power but only 1000v. I have only measured the resonant coil windings in which I have measured current and voltage and then calculated the inductance via the no-load impedance, only the windings in the one leg. Unfortunately, the Variacs seem to be overwhelmed. One is broken complete insulation fault. Greetings Sven
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Von: "onielsen@... [EVGRAY]"
Datum:09.02.2018 18:23 (GMT+01:00)
An: [email protected]
Betreff: Re: Aw: Re: AW: Re: Re: AW: Re: Re: Re: AW: [EVGRAY] Re: All information about Diode Plug.
Hi Sven,
"Actually, I do not need so high voltage-resistant auxiliary thyristors, the resistor is limited by the applied voltage and is only on the power thyristor."
Resistors don't limit the voltage. They limit the current. When current begins to go through a resistor the voltage across it increases proportionally with the current through it. Thus if the thyristor has a lower breakdown voltage than the voltage being applied to it it will still start conducting without any control.
The small thyristor does see the same voltage as the main thyristor minus the gate cathode voltage of the main thyristor.
"I have several options now:
218.615 mH = 450V Urms max.
882,037 mH = 800V Urms max.
1010,000 mH = 800V Urms max.
2274,000 mH = ??????"
Is this the inductance calculated from the impedance at different loads? At no load the full inductance is available. At heavy load most of the inductance is canceled. At least this is how ordinary transformers work.
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hello Ole,
I think you're right with the power diodes between inductor and capacitor, the circle is not closed or permeable in both directions, so no resonance can arise.
I have again made a part of my triggering for the thyristors. I had to use the 1.1 k resistor because the 2.2 K resistor was too large and the current was not enough to ignite the power thyristor. If I take out the diode and replace it with a resistor, I have to reduce the 1.1 K resistor or just remove the diode. Just as the diode plug circuit now works perfectly almost clean sine only slight distortions could risk it.
Unfortunately, I do not get the Tyn1225 auxiliary thyristors cheap anymore, so I do not want to break that much anymore.
Actually, I do not need so high voltage-resistant auxiliary thyristors, the resistor is limited by the applied voltage and is only on the power thyristor.
Last night I again measured the resonance coil of the 3-phase transformer via the impedance and of course got quite different values as my LCR meter had indicated. I will not grow any more so that works very well.
I have several options now:
218.615 mH = 450V Urms max.
882,037 mH = 800V Urms max.
1010,000 mH = 800V Urms max.
2274,000 mH = ??????
My probe is only up to 2.5 kv, and I have at the penultimate measurement already 2.02 kv peak to peak. Although I think that the probe for the peak voltage is specified but one should not challenge his luck.
Anyway, I've driven with the higher voltage and smaller coupling capacitors and have a much better efficiency, so output to input energy.
I have the feeling that the resonance only up to the max. Anything above increases only the reactive current and the voltage does not increase any further, but this only costs input power.
regards
Sven Gesendet: Freitag, 09. Februar 2018 um 03:00 Uhr
Von: "onielsen@... [EVGRAY]" <[email protected]>
An: [email protected]
Betreff: Re: AW: Re: Aw: Re: AW: Re: Re: Re: AW: [EVGRAY] Re: All information about Diode Plug.
Hi Sven,
If the gate was too sensitive an extra resistor could be placed between the gate and the cathode to form a voltage divider with the gate current limiting resistor.
The reason for the extra diode at the variable inductor could be some leftover from an earlier design from before adding the inductor or choke. At least it can be omitted with the two other diodes in place as the current will never go in the reverse direction. Without the inductor (choke) only one diode is needed. The bottom diode is for charging the capacitor and the one sharing its anode (or cathode) is for 'discharging' or demagnetizing the inductor. I.e. the flyback voltage from disrupting the current through the inductor makes the current 'discharge' to the capacitor which is then being charged.
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hi Ole, I'm afraid that over the Powerthyristor cathode on the gate a reverse voltage destroyed the auxiliary thyristor. before I installed the diodes, the thyristors broke, but at the same time we installed the series resistor on the anode side of the auxiliary thyristor, maybe it is the reason that everything runs stable. Somehow you're right, but why did Hector draw the diodes between Variac and capacitor? Greetings Sven
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Von: "onielsen@... [EVGRAY]"
Datum:09.02.2018 00:10 (GMT+01:00)
An: [email protected]
Betreff: Re: Aw: Re: AW: Re: Re: Re: AW: [EVGRAY] Re: All information about Diode Plug.
Hi Sven,
"There are many auxiliary thyristors gone without the diode a series resistor for current limiting I have installed for the auxiliary thyristor as in the drawing. The ignition of the power thyristors has worked very well so far, my idea is more likely to high sensitive thyristors that can be switched with μA thereby would be wasted little energy for the ignition and perhaps rather the synchrony of the system can be achieved."
Diodes don't limit the current very much as they're good conductors in the forward conduction direction. They have a forward conduction voltage drop of around 0.7V or a little more when at heavy load.
"The diode between reactor (Variac) and discharge capacitor should prevent a resonance that can arise between the reactive components"
The other two diodes at the other end of the variac already prevent the current from going in the opposite direction of the first diode at the top end. The top end diode is in series with the double split diodes and the current form either one of the split diodes also goes through the top end diode. Thus the top diode is only introducing another voltage drop (power dissipation) for current going through the variac. This is the brother in law effect (if one's brother in law sells diodes).
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hi Ole, first of all many thanks for your help, I will consider the change with positive diode plugs the ignition energy is removed after the transformer coil and the left diode directly from the capacitor. The charge curve and discharge curve of the two capacitors are almost identical now perfect, now you can work on the vote.
"The small diodes are protecting the small thyristor as the gates of the thyristor are very low ohmic in both directions."
Use resistors instead of diodes when they start conducting. A slight change in voltage gives a big change in current as they are very nonlinear devices "
There are many auxiliary thyristors gone without the diode a series resistor for current limiting I have installed for the auxiliary thyristor as in the drawing. The ignition of the power thyristors has worked very well so far, my idea is more likely to high sensitive thyristors that can be switched with μA thereby would be wasted little energy for the ignition and perhaps rather the synchrony of the system can be achieved.
I think that is still a long way, but a very interesting experiment.
"And why did you mark the Variacs and the protective diodes at the gate of the thyristor power?"
The variacs have the two bottom diodes prevent any current from changing direction. Thus the top diodes at each variac can be omitted as the current through the variacs never changes direction. The voltage across them will change depending on receiving energy or supplying energy."
The diode between reactor (Variac) and discharge capacitor should prevent a resonance that can arise between the reactive components. I will send you the original circuits.
regards
Sven ...