32 •• Appendix A.
Device Selection :
As a guide in selecting R and C,
R : 0.5 to 1 Ω per 1V contact voltage
C : 0.5 to 1 µF per 1A contact current
Value vary depending on the properties of the capacity C acts to
suppress the discharge the moment the contacts open. Resistor R
acts to limit the current when the power is turned on the next time.
Test to confirm. Use a capacitor with a breakdown voltage of 200 to
300V. Use AC type capacitors (non-polarized) for AC circuits.
2. Diode Circuit
This circuit is suitable for DC application. The diode connected in
parallel causes the energy stored in the coil to flow to the coil in the
form of current and dissipates it as joule heat at the resistance
component of the inductive load. This circuit further delays the
release time compared to the RC circuit.
Contact
Inductive
Load
Diode
Device Selection :
Use a diode with a reverse breakdown voltage at least 10 times the
circuit voltage and a forward current at least as large as the load
current. In electronic circuits where the circuit voltages reverse
breakdown voltage of above 2 to 3 times the power supply voltage.
3. Diode & Zener diode Circuit
This circuit is also suitable for DC application. Effective when the
release time i the diode circuit is too long.
Contact
Inductive
Load
Diode
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