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Registered Member #3792
Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136
Yes it was entered, i %$&#@ with the Ext. Resistance field, thank you very much Adrenaline for pointing this out!!! Coilgun Simulator already calculates the coil resistance and you only need to add the REAL external resistance, not the coil resistance (in this case 30 mOhms - the ESR of the capacitor). That means 185 mOhm for the coil and 30 mOhm for the external circuit resistance. But i'm stupid and i added again the coil resistance (185 mOhm + 215 mOhm).....
Wiring resistance is negligible (less than 1 mOhm).
Below is the new system simulation (the correct one).
It seems that the velocity results are much more promising now (49 m/s instead of 41 m/s). And if i implement the V-Switch topology, i may reach the 55 m/s (as indicated by the Coilgun Simulator in the Max Velocity field)!!!
Registered Member #3792
Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136
It has been a long time since the last time i made progress with the project. I came up with an idea for the V - Switch and i need evaluation.
The schematic diagram follows. It works exactly like the original V -Switch. I only changed the voltage rating of C2.
C1 is the main storage capacitor. C2 is the quench capacitor. L1 is the main acceleration coil. D1 and R1 are the BEMF quench components. SCR1 are the main switching thyristors. SCR2 is the quench switching thyristor.
The idea is to turn off the SCR1 not at the time when the current peaks. Instead, we switch it off when the voltage of C1 has reached a certain voltage (here, 100 VDC).
A is the SCR1 turn off point (and SCR2 turn on point). The current drops to 0 (at t = 2 ms) and the voltage of C1 remains at ~100 VDC. That means we have reduced the pulse width time from Toff = 2.7 to Toff = 2 ms, with further reduction of the suckback effect and an increase of the projectile speed.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714
PSCG wrote ...
C1 is the main storage capacitor. C2 is the quench capacitor. L1 is the main acceleration coil. D1 and R1 are the BEMF quench components. SCR1 are the main switching thyristors. SCR2 is the quench switching thyristor.
The idea is to turn off the SCR1 not at the time when the current peaks. Instead, we switch it off when the voltage of C1 has reached a certain voltage (here, 100 VDC).
A is the SCR1 turn off point (and SCR2 turn on point). The current drops to 0 (at t = 2 ms) and the voltage of C1 remains at ~100 VDC. That means we have reduced the pulse width time from Toff = 2.7 to Toff = 2 ms, with further reduction of the suckback effect and an increase of the projectile speed.
Respectful critiques: 1) your schematic shows J2, a 2 pin connector for the SCR triggers. Don't we need two connections for each trigger current source? Here, the cathode connections are common, so a 3-pin connector would suffice for J1. Less importantly, the schematic is missing the capacitor-charging details.
2) Why is C2 so large? It only needs to supply the coil current long enough for SCR1 to turn off. Suppose it were an unpolarized capacitor of 1 to 10 uF, such as a motor-run capacitor? Then D1 and R1 would be un-necessary. As drawn, they protect C2 from back-EMF, and protect C1 from back-EMF if SCR2 is not triggered soon enough.
3) your annotation of point A on the chart doesn't match your description. At 2.0 ms, the voltage on C1 has fallen to zero, and the coil current is still 320 A. That's the current we switch to SCR2 and C2 to turn off SCR1. To do that when V_C1 is 100 volts instead of 0, you need to fire SCR2 at about 1.3 ms, when there's still about 800 amperes in the coil.
Registered Member #3792
Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136
1) The schematic i draw is not a real one. It is just for representation purposes (just to show off the general idea if that helps).
2)The C2 value was chosen as the 1/10 of C1 value, as suggested from Evgenij Vasiljev. Again, this can be changed accordingly. D1 and R1 are included in the case that i cannot find an unpolarized capacitor in my junk box.
3)This is an error i made yesterday while i was making the modification on the simulation (i was too hurried) with the position of the point (it was placed at the wrong section - current instead of voltage graph). The correct simulation follows:
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Reluctance Coilgun Sniper Rifle
