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The Types of Common Relay and How to Choose Relay?

Author: Apogeeweb Date: 12 Mar 2019  2607

relay electricity

Warm hints: This article contains about 3000 words and reading time is about 15 mins.


This article mainly introduces the commonly used relays. Firstly, it introduces the role of relays. Secondly, it introduces which kinds of common relays are used and the types of common relays. Finally, how to choose relays is explained. Let's take a look at this article.

Different Types of Relays



Ⅰ The Role of Relay

Ⅱ Types of Relay

  2.1 Relay Classifications Standard

  2.2 Relay Protection

Ⅲ Models of the Relay

  3.1 Circuit Board Relays

  3.2 General Relays

Ⅳ How to Choose the Relay?

  4.1 Selected by Usage Environment

  4.2 Selected by the Input Signal

  4.3 Selected by Input Parameters

  4.4 Selected by the Load

Ⅰ The Role of Relay

A relay is an electronic control device that has a control system (also called an input loop) and a controlled system (also called an output loop). It is usually used in an automatic control circuit. It actually uses a small current to control the larger An "automatic switch" of current. Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit.

New and Old Graphic Symbol for Relays

Figure 1. Common Relay Graphics and Symbols

Electromagnetic relays are generally composed of a core, a coil, an armature, a contact spring, and the like. As long as a certain voltage is applied to both ends of the coil, a certain current flows in the coil, thereby generating an electromagnetic effect, and the armature will absorb the pulling force of the return spring against the iron core under the action of the electromagnetic force attraction, thereby driving the armature. The moving contact is in contact with the stationary contact (normally open contact).


When the coil is de-energized, the electromagnetic suction force also disappears, and the armature returns to the original position in the reaction force of the spring so that the movable contact and the original static contact (normally closed contact) are released. This is sucked and released, thereby achieving the purpose of turning on and off in the circuit. For the "normally open, normally closed" contacts of the relay, it can be distinguished as follows: a static contact that is in an open state when the relay coil is not energized, called a "normally open contact"; a static contact that is in an on state It is a "normally closed contact".


Ⅱ Types of Relay

2.1 Relay Classifications Standard

Based on different classification methods, the commonly used relays have the following types.

(1) According to the principle of operation: electromagnetic type, induction type, electric type, transistor type relay.

(2) According to the measured parameters: current type, voltage type, power type, impedance type and other power relays, as well as temperature type, pressure type and other non-electricity satin appliances.

(3) According to the function: intermediate relay, time relay and signal relay.

2.2 Relay Protection

The relay protection device realizes the protection of the power grid according to the change of the physical quantity of the parameters of the relevant part of the power grid during normal operation and failure. 

(1) The relay protection with changing reaction current has current quick disconnection, timing overcurrent, inverse time overcurrent and zero sequence current protection.

(2) The relay protection with a change in the reaction voltage has low voltage (or overvoltage) protection.

(3) The reaction current and the current and voltage phase angle change, and there is direction overcurrent protection.

(4) The change value of the reaction voltage and current. That is, the distance between the short-circuit point and the impedance (or distance) of the protection installation is protected by distance.

(5) In case of the difference between the input current and the output current, there is transformer differential protection.

electrical relay

 Models of the Relay

3.1 Circuit Board Relays

(1) Model: 4078 (JRC* 19F)

(2) Model: 40982

(3) Model: 4100F (JRC* 21F) 2

(4) Model: 4123 (T73) 3

(5) Model: JQX* 14FC3

(6) Model: JQX* 115FA4

(7) Model: JQX* 115FB4

(8) Model: JQX* 145F (JQX* 14FL) 5

(9) Model: JQX* 146F (JQX* 14FF) 5

(10)Model: JZC* 22F6

(11) Model: JZC* 32F6

(12) Model: JZC* 33F7

(13) Model: JZC* 35F(TV*5)7

(14) Model: T90* 4115 (JQX* 15F) 8

(15) Model: T91* 4138 (JQX* 16F) 8


3.2 General Relays

(1) Model: AS* 2P* U9

(2) Model: AS* 3P* U9

(3) Model: G2R* 1* S10

(4) Model: G2R* 2* S10

(5) Model: HH52P1

(6) Model: HH53P11

(7) Model: HH54P1

(8) Model: JQX* 10F* 2Z (JTX* 2C) 1

(9) Model: JQX* 10F* 3Z (JTX* 3C) 13

(10) Model: JQX* 13F* 2Z13

(11) Model: JQX* 13FS* 1Z14

(12) Model: JQX* 53F* 2Z14

(13) Model: JQX* 53F* 3Z15

(14) Model: LY115 

(15) Model: LY216

(16) Model: LY3 (HH63P) 16

(17) Model: LY4 (HH64P) 17

(18) Model: MK* 2P17

(19) Model: MK* 3P18

(20) Model: MY218

(21) Model: MY319

(22) Model: MY419

(23) Model: PT52* S20

(24) Model: PT54* S20

(25) Model: TYPE55.0221

(26) Model: TYPE55.0421

(27) Model: TYPE56.0222

(28) Model: TYPE56.0422

(29) Model: TYPE57.0223

(30) Model: TYPE57.0423

(31) Model: TYPE58.0224

(32) Model: TYPE60.224

(33) Model: TYPE60.325

(34) Model: TYPE70.225

(35) Model: TYPE70.326


Ⅳ How to Choose the Relay?

4.1 Selected by Usage Environment

The environmental conditions used mainly refer to temperature (maximum and minimum), humidity (generally referred to as maximum relative humidity at 40 degrees Celsius), low air pressure (excluding heights below 1000 meters), vibration and shock. In addition, there are requirements for packaging methods, mounting methods, external dimensions and insulation. Due to different materials and structures, the environmental mechanical conditions of the relay are different. If it is used under the environmental mechanical conditions specified by the product standard, the relay may be damaged, and it may be selected according to the environmental mechanical conditions of the whole machine or a higher level.


It is best not to use AC-energized relays around devices that are sensitive to electromagnetic interference or radio frequency interference. For DC relays, use a product with a coil transient suppression circuit. Where solid-state devices or circuits provide excitation and are sensitive to spikes, products with transient suppression circuits are also selected.

4.2 Selected by the Input Signal

According to the input signal is electricity, temperature, time, light signal to determine the choice of electromagnetic, temperature, time, photoelectric relay, this is no problem.


Here, the selection of voltage and current relays is specifically described. If the whole machine supplies a constant current to the relay coil, the current relay should be selected. For a constant voltage value, the voltage relay is selected.


4.3 Selected by Input Parameters

The input quantity closely related to the user is the working voltage (or current) of the coil, and the pull-in voltage (or current) is the parameter that the relay manufacturer controls the sensitivity of the relay and judges and evaluates it.


For the user, it is just a working limit parameter value. The control safety factor is the working voltage (current) / pull-in voltage (current). If the relay is used under the pull-in value, it is unreliable and unsafe. If the ambient temperature rises or is under vibration or shock conditions, the relay will be made. The work is not reliable.


When designing the whole machine, the no-load voltage can not be used as the basis of the working voltage of the relay. Instead, the coil should be connected as the load to calculate the actual voltage, especially when the internal resistance of the power supply is large.


When the triode is used as the switching element to control the on/off of the coil, the triode must be in the on-off state. For relays operating below 6 VDC, the saturation voltage drop of the triode should also be deducted.


Of course, the higher the working value is, the higher the better. If the rated working value is too high, the impact wear of the armature will increase, the number of contact rebounds will be increased, and the electrical life will be shortened. Generally, the working value is 1.5 times of the suction value. The error is generally ±10%.

4.4 Selected by the Load

Long-term practice at home and abroad has proven that about 70% of faults occur on contacts, which is important to properly select and use relay contacts.


The contact combination form and the number of contact groups should be determined according to the actual situation of the controlled loop. The commonly used contact combinations are shown in Table 6. The moving contact group in the moving contact group and the switching contact group has a lower load returning degree and a larger compensation amount after the contact is ablated, and the load capacity and contact reliability are lower than the dynamic breaking contact. The set of the breaking contact in the group and the switching contact group is high, and the whole circuit can be adjusted by appropriately adjusting the position of the contact, and the moving contact is used as much as possible.


It is important to determine the parameters based on load capacity and load characteristics (resistance, inductive, capacitive, lamp load, and motor load). It is considered that the contact switching load is small and reliable than the switching load. Generally speaking, the relay switching load is rated at a rated voltage, and the current is greater than 100 mA, which is preferably less than 75% of the rated current. If the current is less than 100 mA, the carbon deposit in the contact will increase and the reliability will decrease. Therefore, 100 mA is called the test current, which is the assessment content of the professional standards of the relay manufacturer and the level of the process. Since the general relay does not have low-level switching capability, the relay is used to switch the load of 50mV and 50μA or less. The user should indicate that the relay manufacturer should assist in the selection if necessary.


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