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Parameters, types and selection method of electromagnetic re

时间:2019-10-10 17:23
The electromagnetic relay is a kind of component in the automatic control circuit. In fact, it is a kind of automatic switch with low current control. Therefore, it is widely used in electronic devices. The electromagnetic relay generally consists of a core, a coil, consisting of several groups of contacts with reed. The contact points of the movable contact and the static contact point, in the work process can act as the contact, can not act as the static contact.
Electromagnetic relay works like this: when the coil is energized after, core is magnetization generates electromagnetic force is large enough, attract the armature and promote reed, so that the movable contacts and static contacts are closed or separated; when the coil power, the electromagnetic force disappears, armature returning the original position, the movable contacts and static contacts and back to the original closed or separated from the state. When using the need to control the circuit to receive the contact, the use of the relay to achieve the purpose of control.
In the following, the characteristics of electromagnetic relay, type of symbol and application principle are briefly introduced.
Characteristic parameters: the main characteristic parameters of electromagnetic relay are as follows:
1 rated working voltage or rated working current: This refers to the voltage or current of the coil when the relay is working. The structure of a type of relay is roughly the same. In order to adapt to different voltage of the circuit application, a type of relay usually has a variety of rated operating voltage or rated current, and the specification model to be different.
2 direct current resistance: This is the DC resistance of the coil. Some product specifications are given in the rated operating voltage and DC resistance, then can be calculated according to Ohm's law. Rated working voltage can be obtained if the rated operating current and the DC resistance are known.
3 pull current: it refers to the minimum current relay can produce pull action. In actual use, the relay is attracted reliably, a given voltage can be equal to or slightly higher than the rated voltage. Do not generally greater than 1.5 times the rated operating voltage. Otherwise it will burn the coil.
4 release current: it refers to the maximum current of the relay to release the action. If the decrease in attracting state relay current, when the current decreases to a certain degree of relay back to is not energized state, this process is called relay release action. The current release is much smaller than the current.
5 contact load: it refers to the voltage or current of the relay contact. It determines the size of the relay to control the voltage and the current. When the application can not be used to control large current or high voltage with little contact load. For example: the contact load of JRX-13F electromagnetic relay is 0.02A 12V, it can not be used to control the circuit of 220V.
Electric sign and contact form of relay. Relay coil in the circuit with a rectangular box symbol, if the relay has two coils, draw two parallel rectangular box. At the same time in a rectangular box or a rectangular box next to the symbol of the relay of the text symbols "J". There are two ways to express the contact of the relay: one is to draw them directly on the side of the box, which is more intuitive. The other one is according to the requirements of the circuit is connected to all the contacts were painted to the respective control circuit, usually on the side of the same relay contacts and coils are marked on the same text symbols and contact group on the number, to show the difference. Relay contacts have three basic forms:
1 type (H type, foreign: A type) coil is not energized when the two contact is disconnected, power, the two contacts on the closure. The word phonetic prefix "H" said.
2 move off type (D type, foreign: B type) coil is not energized when the two contact is closed, the power after the two contact is broken. With the hyphenation of phonetic prefix "D" said.
3 conversion type (Z type, C type abroad: This is the contact type). This contact group consists of three contacts, that is, the middle is the contact, the upper and lower a static contact. When the coil is energized, the movable contact and one of the static contacts are disconnected and the other is closed. The movable contact is moved, so that the original opening is closed, the original closed state, and the purpose of the conversion is achieved. Such a contact group is called a converting contact. With the "turn" word phonetic prefix "Z" said.
In addition, a relay can also have one or more contact groups, but it is nothing more than three forms. In the circuit diagram, the contact and the contact group of the drawing, the provisions of the state of the state when the power is not.
Relay selection:
1 to understand the necessary conditions: first control circuit power supply voltage, the maximum current can be provided, the voltage and current in the control circuit, the control circuit requires a few groups, what form of contact. Selection of relay, the general control circuit of the power supply voltage can be used as the basis for selection. The control circuit should be able to provide adequate working current to the relay, or relay is not stable.
2 access to relevant information to determine the use of conditions, can find the relevant information to find out the need for the relay model and specification number. If you have the relay, can be used to check whether the data. Finally consider the size is appropriate.
3 to pay attention to the volume of apparatus. If used for general electrical appliances, in addition to the consideration of the case of the volume, the main consideration of the circuit board layout. For small electrical appliances, such as toys, remote control device should be used to select the super miniature relay products.
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