The definition of the relay: Relay is an automatic control system component that produces a jump change in cardiac output when the output (electricity, magnetism, sound, light, heat) reaches a certain value.
When the output (such as voltage, current, temperature, etc.) reaches the standard value, the household appliance that makes the controlled output power circuit turn on or off. It can be divided into electrical equipment quantity (such as current, voltage, frequency, output power, etc.) relays and non-electricity (such as temperature, working pressure, speed, etc.) relays. It has the advantages of fast posture, stable work, long service life, and small size. It is widely used in power engineering maintenance, automation technology, fitness sports, remote control, precision measurement, and communication equipment.
Relay is a kind of electronic device control element. It has an automatic control system (also called an input control loop) and an automatic control system (also called output control loop). It is generally used in fully automatic control loops. In fact, it uses smaller Electric current is a kind of "control switch" that manipulates large currents. Therefore, it has the functions of automatic adjustment, safety maintenance, and conversion of the power circuit in the power circuit.
1. The principle and characteristics of electromagnetic induction relay
Relay type Automatic Voltage Regulator AVR
Inductive relays are generally composed of transformer cores, coils, current coils, and contact springs. If a certain voltage is applied to both sides of the coil, a certain current will pass through the coil, which will cause electromagnetic effects. The flowing coil will get rid of the effect of the magnetic field force and return to the elastic tensile force to attract the transformer iron. The core, and then push the moving contact and the static contact (open and close contact) of the flow coil to attract.
When the coil is turned off, the adsorption force of electromagnetic induction also fades, and the flow coil will return to the original position under the rebound force of the yellow spring so that the moving contact and the original static contact (normally closed contact) are attracted. That way, it pulls in and releases it, and then achieves the purpose of on-off and off in the power circuit. Regarding the "open and closed, normally closed" contacts of the relay, it can be distinguished as follows: the static contact that is in the off state when the relay coil is not connected to the power supply is called "open and closed contact"; The static contact of the situation is called "normally closed contact".
2. The principle and characteristics of the thermistor reed relay
The thermistor reed relay is a new type of thermal switch that uses thermistor permanent magnet material to inspect and manipulate temperature. It is composed of a temperature sensor magnetic ring, constant magnetic ring, dry reed tube, heat transfer mounting sheet, a plastic substrate, and some notes. The thermistor reed relay does not need a coil excitation regulator, but the magnetic driver power switch posture caused by the constant magnetic ring. Whether the constant magnetic ring can show the magnetism to the reed switch is determined by the temperature control characteristics of the temperature sensor magnetic ring.
3. The principle and characteristics of the solid-state relay (SSR)
The solid-state relay is a kind of two wiring terminals as input terminals, and the other two wiring terminals are output terminals with four-terminal components. The protective components are selected in the middle to complete the electrical protection of the output.
Solid-state relays can be divided into communication AC type and DC type according to the type of load switching power supply. According to the form of the power switch, it can be divided into on and off type and normally closed type. According to the protection from, it can be divided into composite type, transformer protection type, and optical protection type, with the most number of optical protection type.
1. Measuring the contact resistor
Use the resistor file of the multimeter to accurately measure the normally closed contact and the moving point resistor. The resistance value should be 0, (the contact resistance value can be measured within 100 milliohms with a more accurate method); The resistance value of the close contact and the moving point is infinite. It can be distinguished that which is a normally closed contact and which is an open and close contact.
2. Measuring coil resistor
The resistance value of the relay coil can be accurately measured with a multimeter in the R×10Ω file, and then it can be distinguished whether the coil has a leading condition.
3. Accurately measure the pull-in voltage and pull-in current
11 relay-type automatic voltage regulators
Find an adjustable regulated power supply and an ammeter, enter a set of voltages for the relay, and string an ammeter into the control loop of the power supply system for testing. Gradually increase the switching power supply voltage, and when you hear the sound of the relay, record the pull-in voltage and pull-in current. Can be accurate, can try several times to find the average.
4. Accurately measure the released voltage and released current
It is also connected and tested as described. When the relay is closed, slowly reduce the voltage of the power supply system. When you hear the relay beep again, record the voltage and current at this time. You can also try a few more times. And obtain the average value of the released voltage and release current. Under normal circumstances, the released voltage of the relay is about 10-50% of the pull-in voltage. If the released voltage is very small (less than 1/10 of the pull-in voltage), it cannot be used normally. The reliability of the circuit leads to threats and unreliable work.
The electrical marking and contact mode of the relay:
The relay coil is represented by a long box symbol in the power circuit. If the relay has two coils, draw two long frames side by side. In addition, mark the letter symbol "J" of the relay inside or beside the long frame.
There are two ways to express the contacts of the relay: one is to draw them immediately on the side of the long frame, which is more visualized. The other is to draw each contact into a separate control loop according to the power supply circuit connection. Generally, the same letters and symbols are marked on the contacts and coils of the same relay, and the contact groups are grouped. No. to show the difference.
1. The two contacts of the moving-on (H-type) coil are disconnected when the power is not connected. After the power is connected, the two contacts are closed. It is expressed with the pinyin prefix "H" of the ligature.
2. The two contacts of the movable-break (D-type) coil are closed when the power is not connected, and the two contacts are broken after the power is connected. Use hyphenated pinyin prefix "D" to express.
3. Conversion type (Z type) is a contact group type. There are three contacts in this type of contact group, that is, there is a moving contact in the middle and a static contact on the left and right. When the coil is not connected to the power supply, the moving contact and one of the static contacts are broken and the other is closed. After the coil is connected to the power supply, the moving contact will move, so that the originally broken will be closed and the previously closed contact will be broken.