Body
Hi Sven,
Yahoo seems to be quite unstable at the moment. No attachment and no pasted image neither! Here's the message. The image is pasted below as the message may be truncated after pasting.
Hi Sven,
Just lost my answer. I'll try again.
"The small diodes are protective diodes to protect the small thyristor as the gates of the power thyristors are very low ohmic in both directions. "
Use resistors instead as diodes have very low impedance when they starts conducting. A slight change in voltage gives a big change in current as they are very nonlinear devices.
"I think to remove the dashed line and connect the ignition in front of the transformer coil but on the right is that also so and why is that a monitoring?"
Exactly! The left hand side triggering circuit has one voltage drop more than the circuit on the right hand. It sees the voltage across the primary coil to the left. The right hand side triggering circuit doesn't see the voltage across the primary winding to the right. Thus the left hand side depends on what happens across the primary winding which the right hand side doesn't do.
Monitoring the voltage (U_left or U_right) across each capacitor for triggering the SCRs is what is being done. At least it's being done at the right hand side while at the left hand side the voltage across the capacitor plus the voltage across the primary is being monitored. The rest of the voltage drops (blue arrows) are constants determining the triggering voltage.
"And why did you mark the Variacs and the protective diodes at the gate of the power thyristors?"
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.
Regards
Ole
---In [email protected], <onielsen@...> wrote :
Hi Sven,
Just lost my answer. I'll try again.
"The small diodes are protective diodes to protect the small thyristor as the gates of the power thyristors are very low ohmic in both directions. "
Use resistors instead as diodes have very low impedance when they starts conducting. A slight change in voltage gives a big change in current as they are very nonlinear devices.
"I think to remove the dashed line and connect the ignition in front of the transformer coil but on the right is that also so and why is that a monitoring?"
Exactly! The left hand side triggering circuit has one voltage drop more than the circuit on the right hand. It sees the voltage across the primary coil to the left. The right hand side triggering circuit doesn't see the voltage across the primary winding to the right. Thus the left hand side depends on what happens across the primary winding which the right hand side doesn't do.