A
Arie de Muynck
- Jan 1, 1970
- 0
"Ken Smith" ...
Zerocrossing turnon does only load the resistor at turnoff - and then the
current wil be very low. No problem for the snubber R.
The circuit can be phase controlled which is a problem for the the resistor.
My problems with sparking resistors were in a phase-controlled motordrive,
mostly running at 50% phase and with a rather big C, so a heavy currentspike
at each turnon.
BTW: you must compute the proper values for a given circuit. Using a
low-impedance snubber with small solonoid controlled valves may cause the
valves to stay activated by the snubber current!
Regards,
Arie de Muynck
So, the spike like current in the resistor is a current that starts equal
to mains/R and then decreases very rapidly.
Does the triac get turned on only at zero crossings in this application or
is it phase controlled? If it is turned on at zero crossings, there is a
reduced requirement on the resistor. In the phase controlled case, the
resistor can end up with 4 spikes of almost a big per cycle.
Zerocrossing turnon does only load the resistor at turnoff - and then the
current wil be very low. No problem for the snubber R.
The circuit can be phase controlled which is a problem for the the resistor.
My problems with sparking resistors were in a phase-controlled motordrive,
mostly running at 50% phase and with a rather big C, so a heavy currentspike
at each turnon.
BTW: you must compute the proper values for a given circuit. Using a
low-impedance snubber with small solonoid controlled valves may cause the
valves to stay activated by the snubber current!
Regards,
Arie de Muynck