Understanding Control Relays: Types, Functions, and Applications
About Control Relay
A control relay is known as a Relay, is a switch, an electromagnetic switch. A control relay allows electrical current to flow through a conducting coil that opens or closes a switch. It also protects the circuit current. With a control relay, users do not need to manually turn the switch to isolate or change the state of an electric circuit. Currently, control relays play a crucial role in today’s electronic devices. They are electronic parts that power electronic parts such as motors, power plants, power supply systems, transistors, and many more. In this article, we will discuss all control relays, from how they work to what they are used for.
Understanding Contact Type of a Relay
Every Control Relay has a Contact type such as SPST-NO but what does it mean?
Poles represent the number of circuits controlled by a switch. Throws represent the number of positions the switch can adopt.
- Single Pole Single Throw (SPST) has two terminals that can be connected and disconnected. Including two for the coil, such a relay has four terminals in total. Single Pole Double Throw, SPDT, has a common terminal that connects either one of two others. Including two for the coil, this relay has five terminals in total. Regardless of whether the coil is active or inactive, either ‘A’ or ‘B’ is always resting while the other needs to be the coil to be powered.
- Double Pole Single Throw (DPST) is equal to two SPST activated by a single coil. Including two for the coil, this relay has 6 terminals in total. Double Pole Double Throw, DPDT is equal to two SPDTs activated by a single coil. Including two for the coil, this relay has 8 terminals in total.
What Are the Parts of an Control Relay?
All control relays come with the following components:
- Mechanically movable contact
- Electromagnet
- Spring
- Switching points
You can make an electromagnet by winding a copper coil on any metal core. The two ends of the copper coil will be connected to the two pins of the relay. Generally, relays have three contact points, also known as switching points. The contacts are known as normally open (NO), common (COM), and normally close (NC) contacts.
A relay can be used in AC as well as DC circuits.
Difference between Normally Open (NO) and Normally Closed (NC) contacts
NO contacts allow current when the relay is energized. This means when there is voltage, the contact closes and allows current to flow through. NC contacts allow current when the relay is not energized. Opposite to NO, NC contact opens and interrupts the current flow. *Change Over (CO) is the same as Double Throw (DT) relay.
Shop for Control Relays
ElectGo offers control relay products from various brands including ABB, OMRON, and SCHNEIDER ELECTRIC, WEIDMULLER. As an authorized distributor in Singapore, we are your trusted source for high-quality control relay products from these leading manufacturers.
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CM-MSS.13S Therm. motor protec. relay 1c/o, 110-130VAC/220-240VACABB
SKU: AB_1SVR730700R2100
Model: CM-MSS.13S
SGD $79.69 -
CM-MPS.41S Three-phase monitoring relay 2c/o, 0,0.1-30s, L1-L2-L3=3x300-500VACABB
SKU: AB_1SVR730884R3300
Model: CM-MPS.41S
SGD $250.94 -
CR-P230AC2 Pluggable interface relay 2c/o, A1-A2=230VAC, 250V/8AABB
SKU: AB_1SVR405601R3000
Model: CR-P230AC2
SGD $10.42 -
CR-PSS Standard socket for 1c/o or 2c/o CR-P relaysABB
SKU: AB_1SVR405650R1000
Model: CR-PSS
SGD $7.27 -
CT-MBS.22P Time relay, multifunction 2c/o, 24-48VDC, 24-240VACABB
SKU: AB_1SVR740010R3200
Model: CT-MBS.22P
SGD $151.15 -
CM-TCS.11P Temperature monitoring relay Temp.-range -50...+50°C, 24-240VAC/DCABB
SKU: AB_1SVR740740R0100
Model: CM-TCS.11P
SGD $271.89 -
CM-MPS.23S Three-phase monitoring relay 2c/o, 0,0.1-30s, L1-L2-L3-N=3x180-280VACABB
SKU: AB_1SVR730885R4300
Model: CM-MPS.23S
SGD $313.92 - CM-MPS.11S Three-phase monitoring relay 2c/o, 0,0.1-30s, L1-L2-L3-N=3x90-170VAC
ABB
SKU: AB_1SVR730885R1300
Model: CM-MPS.11S
SGD $266.69 -
CM-MSS.32S Therm. motor protec. relay 2c/o, 24VAC/DCABB
SKU: AB_1SVR730712R0200
Model: CM-MSS.32S
SGD $93.50 - CM-MPS.43S Three-phase monitoring relay 2c/o, 0,0.1-30s, L1-L2-L3=3x300-500VAC
ABB
SKU: AB_1SVR730884R4300
Model: CM-MPS.43S
SGD $298.18 -
CM-MSS.23S Therm. motor protec. relay 2c/o, 110-130VAC/220-240VACABB
SKU: AB_1SVR730700R2200
Model: CM-MSS.23S
SGD $87.08 - CM-MPS.21S Three-phase monitoring relay 2c/o, 0,0.1-30s, L1-L2-L3-N=3x180-280VAC
ABB
SKU: AB_1SVR730885R3300
Model: CM-MPS.21S
SGD $261.36 -
CM-MSS.33S Therm. motor protec. relay 2c/o, 110-130VAC/220-240VACABB
SKU: AB_1SVR730712R2200
Model: CM-MSS.33S
SGD $93.50 - CM-MPS.31S Three-phase monitoring relay 2c/o, 0,0.1-30s, L1-L2-L3=3x160-300VAC
ABB
SKU: AB_1SVR730884R1300
Model: CM-MPS.31S
SGD $256.15 -
CM-MSS.12S Therm. motor protec. relay 1c/o, 24VAC/DCABB
SKU: AB_1SVR730700R0100
Model: CM-MSS.12S
SGD $79.69 -
CM-SRS.21S Current monitoring relay 2c/o, B-C=3mA-1A RMS, 220-240VACABB
SKU: AB_1SVR730841R1400
Model: CM-SRS.21S
SGD $198.38 -
CM-MSS.22S Therm. motor protec. relay 2c/o, 24VAC/DCABB
SKU: AB_1SVR730700R0200
Model: CM-MSS.22S
SGD $87.08 -
CM-SRS.11S Current monitoring relay 1c/o, B-C=3mA-1A RMS, 220-240VACABB
SKU: AB_1SVR730841R1200
Model: CM-SRS.11S
SGD $177.43 -
CM-MSS.41S Therm. motor protec. relay 2c/o, 24-240VAC/DCABB
SKU: AB_1SVR730712R1200
Model: CM-MSS.41S
SGD $156.48 -
CM-MSS.31S Therm. motor protec. relay 1n/o+1n/c, 24-240VAC/DCABB
SKU: AB_1SVR730712R1400
Model: CM-MSS.31S
SGD $156.48
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MY4N-GS DC24 Relay and PYFZ-14-E Socket (Set)Omron
SKU: OM_MY4-5509B
Model: MY4N-GS DC24 BY OMZ
SGD $6.65 - MY4N-GS AC220/240 Relay and PYFZ-14-E Socket (set)
Omron
SKU: OM_MY4-5508D
Model: MY4N-GS AC220/240 BY OMZ
SGD $6.65 -
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Socket RXZ - Mixed Contact -10A - < 250V - Screw Clamp -for Relay RXM2.., RXM4..Schneider
SKU: SE_RXZE2M114
Model: RXZE2M114
SGD $5.06 -
Socket RXZ - Mixed Contact - 10A - < 250V - Connector - for Relay RXM2.., RXM4..Schneider
SKU: SE_RXZE2M114M
Model: RXZE2M114M
SGD $5.85 -
Harmony, Modular 3-phase Supply Control Relay, 8 A, 2 CO, 183…528 V ACSchneider
SKU: SE_RM22TG20
Model: RM22TG20
SGD $80.86 -
Harmony, Socket, for RXM2LB Relays, 7 A, Screw Connectors, Mixed Contact.Schneider
SKU: SE_RXZE1M2C
Model: RXZE1M2C
SGD $3.13 -
Socket RXZ - Separate Contact - 12 A - < 250 V - Connector - for Relay RXM2..Schneider
SKU: SE_RXZE2S108M
Model: RXZE2S108M
SGD $4.33 -
Harmony, Miniature Plug-in Timing Relay, 5 A, 2 CO, 0.1 S..100 H, On-Delay, 230 V ACSchneider
SKU: SE_REXL2TMP7
Model: REXL2TMP7
SGD $40.62 -
Voltage Control Relay RM17-U - Range 65..260 V AC/DCSchneider
SKU: SE_RM17UBE15
Model: RM17UBE15
SGD $140.10 -
Harmony, Modular 3-phase Supply Control Relay, 5 A, 2 CO, 380...480 V ACSchneider
SKU: SE_RM22TA33
Model: RM22TA33
SGD $161.31 -
Socket RXZ - Separate Contact - 10 A - < 250 V - Connector - for Relay RXM4..Schneider
SKU: SE_RXZE2S114M
Model: RXZE2S114M
SGD $5.85 -
Harmony, Modular 1-phase Voltage Control Relay, 8 A, 2 CO, 1…100 V AC/DC, 24…240 V AC/DCSchneider
SKU: SE_RM22UA32MR
Model: RM22UA32MR
SGD $187.24 -
Harmony, Miniature Plug-in Timing Relay, 5 A, 4 CO, 0.1 S..100 H, On-Delay, 230 V AC.Schneider
SKU: SE_REXL4TMP7
Model: REXL4TMP7
SGD $42.82 -
Metal Maintaining Clamp - for Miniature Relay Socket RXZSchneider
SKU: SE_RXZ400
Model: RXZ400
SGD $11.37 -
Harmony, Socket, for RXM2LB/RXM4LB Relays,7 A, Screw Connectors, Mixed Contact.Schneider
SKU: SE_RXZE1M4C
Model: RXZE1M4C
SGD $3.92 -
Harmony, Modular 3-phase Undervoltage Control Relay, 8 A, 2 CO, 380…480 V ACSchneider
SKU: SE_RM22TU23
Model: RM22TU23
SGD $111.90 -
Harmony, Modular 3-phase Voltage Control Relay, 8 A, 2 CO, 380...480 V ACSchneider
SKU: SE_RM22TR33
Model: RM22TR33
SGD $161.31 -
Socket RXZ - Separate Contact - 10 A - < 250 V - Connector - for Relay RXM3..Schneider
SKU: SE_RXZE2S111M
Model: RXZE2S111M
SGD $5.85 -
Harmony, Modular Timing Relay, 8 A, 1 CO, 0.05 S…300 H, Power On Delay , 24...240 V AC/DC.Schneider
SKU: SE_RE22R1AMR
Model: RE22R1AMR
SGD $92.89 -
Harmony, Modular Timing Relay, 8 A, 2 CO, 0.05 S…300 H, Power On Delay , 24...240 V AC/DC.Schneider
SKU: SE_RE22R2AMR
Model: RE22R2AMR
SGD $120.35 -
power relay plug-in - Harmony RPF - 2 CO - 24 V DC - 30 ASchneider
SKU: SE_RPF2BBDBB
Model: RPF2BBDBB
SGD $13.69 -
miniature plug-in relay - Zelio RXM4L - 4 C/O - 110 V DC - 3 A - with LEDSchneider
SKU: SE_RXM4LB2FD
Model: RXM4LB2FD
SGD $6.05
Frequently Asked Questions (FAQs)
1. How do control relays work?
The main principle on which an electronic relay function is that of electromagnetic induction. When current passes through the electromagnet, a magnetic field is created around it. There is the use of a switch for applying direct current (DC) to the load. When there is the application of direct current (DC) in the coil, it attracts contact. This is known as energizing the relay and when there is the removal of the supply, the relay reaches back to its original position. This is called the de-energizing of the relay.
Interestingly, there are relays, where the contacts are initially closed. The circuit only opens when there is an electrical supply.
Solid state relays come with sensing elements for detecting the input voltage and switching the output with the use of a technique called Opto-coupling
2. What are control relay devices used for?
The main function of a control relay is to allow the flow of electric current through a conducting coil, which closes or opens a switch. It also plays a role in protecting the circuit from current surges. When there is a control relay in place, there is no need to operate the switch manually to change or isolate the state of the electric current.
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