Final answer:
To design an R-C contact protection network for the given circuit, we need to calculate the value of the resistor (R) and capacitor (C) that will provide adequate protection to the platinum contacts of the switch.
Step-by-step explanation:
To design an R-C contact protection network for the given circuit, we need to calculate the value of the resistor (R) and capacitor (C) that will provide adequate protection to the platinum contacts of the switch. The relay coil has a resistance of 400 ohms and operates from a 30V DC supply. One way to protect the contacts is by using an R-C snubber circuit. A snubber circuit is commonly used to suppress voltage spikes and protect the contacts from arcing.
First, we need to calculate the value of the resistor (R). We can use Ohm's Law (V=IR) to determine the current flowing through the coil. Since the supply voltage is 30V and the resistance of the coil is 400 ohms, we can calculate the current using the formula I=V/R. I=30V/400ohms = 0.075A.
Now, we can calculate the value of the capacitor (C) using the time constant formula. The time constant (T) of an R-C circuit is given by the formula T=RC, where R is the resistance and C is the capacitance. Typically, the time constant is chosen to be at least 5 times the contact bounce time for effective protection. The contact bounce time is the time it takes for the contacts to settle down after being closed. Let's assume a contact bounce time of 10ms. The time constant (T) should be at least 50ms (5 times the contact bounce time).
To calculate the value of the capacitor (C), we rearrange the time constant formula to solve for C: C = T/R. C=50ms/400ohms = 0.125uF.