I'm designing a PCB with a PIC micro-controller that has to switch some contactors. This PIC drives some NPN BJT transistors and these transistors drive some Relays that switch the contactors.
I'm trying to minimize EMI interference and sparks in my circuit and for thus i have to decide what coils to use on the contactors (and snubbers but thats not related to the question).
Seaching for contactors I've got two models (for the coil):
1) 7VA, cos(phi)=0.3 (50Hz), 24VAC.
2) 7VA, cos(phi)=0.3 (50Hz), 220VAC.
What's the comparison between both voltage spikes when the coil is suddenly opened ? (How much higher, how much longer, frequency, etc)