Parallel and series connection of relay contacts

Current, like water flow, flows from the positive pole to the negative pole.
1. Parallel shunt?

On the main road, the water flow is the highest, that is, the current is the highest.

The water flow on the branch road is equivalent to the diversion of the main road.

The sum of tributaries is equal to the flow of water on the main road.

Therefore, we know parallel shunting.

2. Series voltage divider?

Each resistor is equivalent to a dam gate, and the water flow passes through each dam gate;

The height of the water flow will decrease, which means the water potential will decrease.

The difference in water flow on both sides of each resistor (dam) is the voltage (potential difference).

Therefore, series voltage sharing.

Parallel and series connection of relay contacts

The use of contacts in parallel cannot increase their load current, because the action of multiple sets of contacts in a relay is absolutely different, that is, it is still the load of a set of contacts after switching and increasing, which can easily damage the contacts without contact or welding and cannot be disconnected. Parallel connection of contacts can reduce the failure rate for "breaking" errors, but the opposite is true for "sticking" errors. Due to the main failure mode of contact errors being "break" errors, parallel connection should be recognized for improving reliability and can be used in key parts of equipment. But the voltage used should not be higher than the maximum working voltage of the coil, nor should it be lower than 90% of the rated voltage, otherwise it will endanger the lifespan and reliability of the coil.

The series connection of contacts can increase their load voltage, and the multiple increase is the number of sets of series contacts. The series connection of contacts can improve its reliability (voltage sharing) for "sticking" errors, but the opposite is true for "breaking" errors. In summary, when using redundancy technology to improve the reliability of contact operation, it is important to pay attention to the nature, size, and failure mode of the load.