Relays serve several functions:
1. Expand the control range: for example, when the control signal of multi-contact relay reaches a certain value, the multi-circuit can be changed, broken and put on at the same time according to different forms of contact group.
2, amplification: for example, sensitive relays, intermediate relays, etc., with a very small amount of control, can control a large power circuit.
3. Integrated signals: for example, when multiple control signals are input into multi-winding relays in a prescribed form, the predetermined control effect is achieved through comparison and integration.
4, automatic, remote control, monitoring: for example, the relay on the automatic device, together with other electrical appliances, can form a control circuit, so as to achieve automatic operation.
Relay (English name: relay) is a kind of electric control device, which causes predetermined step change of the controlled quantity in the electrical output circuit when the change of the input quantity (excitation quantity) reaches the specified requirements. It has an interactive relationship between the control system (also known as input loop) and the controlled system (also known as output loop). Usually used in automatic control circuits, it is actually a "automatic switch" that USES a small current to control a large current. Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit.
Influencing factors of relay reliability:
1. Influence of environment on relay reliability: the average time between failures of the relay operating under GB and SF is the highest, reaching 820000h, while under NU, it is only 60000h.
2. Influence of quality grade on relay reliability: when the relay with A1 quality grade is selected, the average time between failures can reach 3660000h, while the average time between failures of the relay with C grade is 110000, with a difference of 33 times. It can be seen that the quality grade of the relay has a great influence on its reliability.
3, the influence on the reliability of the relay contact form: relay contact form will also affect its reliability, single throw the reliability of the relay type were higher than the number of the same knife type double throw relay, reliability gradually reduce with the increase of the number of knife at the same time, is the average time between failures single-pole single-throw relay four knife double-throw relay of 5.5 times.
4. Influence of structure types on relay reliability: there are 24 structure types of relays, all of which have influences on their reliability.
5. Influence of temperature on relay reliability: the operating temperature range of the relay is between -25 ℃ and 70℃. With the increase of temperature, the mean time between faults of relay decreases gradually.
6. Influence of operation rate on relay reliability: with the improvement of relay operation rate, the mean time between failures basically presents an exponential downward trend. Therefore, if the designed circuit requires the relay to operate at a very high speed, the relay needs to be carefully tested during circuit maintenance so that it can be replaced in time.
7. Influence of current ratio on relay reliability: the so-called current ratio is the ratio of the working current of the relay to the rated load current. Current ratio has great influence on the reliability of the relay, especially when the current ratio greater than 0.1, the average time between failures drops rapidly, and the current ratio is less than 0.1, the average time between failures, so should choose rated current in circuit design larger load in order to reduce the current ratio, which can guarantee the relay and the whole circuit is not due to the fluctuations of the working current and lower reliability.