A Relay is a switching device that may operate electronically or mechanically. Electromagnetic Relays are widely used in machine tool control, industrial assembly lines, and commercial equipment. They are easily available from relay manufacturing companies.
One of the main reasons why relays are much popular is because they can control a large amount of output. And we are all aware that the output in an electronic device is much higher than the electrical input received.
The implementation of a relay is significant in two given situations -
- When it is important to have a low power signal controlling the circuit
- When there are several circuits aimed to be controlled by the same signal.
Electromagnetic relays apparently are the earliest relays, used since the 1830s. The best attribute about an electromagnetic relay, when compared to other types of relays is that they use less energy.
Now, let us get into the topic and understand the structure of an electromagnetic relay-
An electromagnetic relay is composed of electromagnet, armature, spring, movable contact and a stationary contact.
A relay is capable of handling the high power needed to directly control a load but the difference is of voltage.
Usually, an electromagnetic relay has two circuits - namely low-voltage control circuit and high-voltage working circuit.
The low-voltage control circuit has an electromagnetic relay coil, a low-voltage power supply and also a switch.
Whereas, the high-voltage working circuit consists of a high-voltage power supply, a motor and other contacts of the electromagnetic relay.
Working Principle – Electromagnetic Relays
The working mechanism of electromagnetic relays is simple to understand. The electromagnetic relay operates largely as per the principle of electromagnetic induction, which also means that as the electric current is passed on the conductor, the conductor behaves like a magnet.
So, as you switch on the power in the low-voltage control circuit, the current goes through the coil of the electromagnet and the coil gets activated by a supply system. Thus, generates a magnetic field.
On this, the armature generates a suction force to connect the movable contact and stationary contact.
The power circuit of the motor switches on and it starts to work.
The process of switching off -
When it comes to switching off the power in the low-voltage control circuit, the current in the coil will disappear, the armature under the action of the spring separates the movable contact and stationary contact.
The working circuit is hence, disconnected and the motor stops working.
The aforementioned process was the switching on and off of the electromagnetic relays. However, the ‘on’ and ‘off’ status relies on electromagnets to control the status of operating circuits.
Usually, when a voltage is generated on both the ends of the coil, the coil gets filled with current and generates an electromagnetic effect.
The electromagnet effect attracts the armature to the iron core against the tension of spring in order to pull the movable contact of the armature to the stationary NO (normally open) contact.
In the process to switch off, the attraction of the electromagnet disappears. Further, the armature gets back to its initial position under tension of the spring to part the movable contact from the stationary contact (normally closed contract or NC).
The pulling and releasing activities are conducted to control a simultaneous opening and closing of the circuit.
And how do you understand if the state is on or off?
You could make out from the state of the stationary contact.
When the coil is cut off from the power, then the stationary contact is the ‘on’ state and the coil is connected to the power if stationery contact is in ‘off’ state.
Electromagnetic relays are the oldest type of relays used in the market. Even after many types of additions in the market, the role of electromagnetic relays is constant.
However, there are also the latest electromagnetic relays coming in the market. For which, you can contact a relay manufacturer in India, to know the latest developments.
Check out our various range of products here:
How to test an electromagnetic relay?
Relay manufacturers in India are experts in testing the EMRs. Once you understand the characteristics and working principles of an electromagnetic relay, it is worth knowing the process of testing an electromagnetic relay. Once you are aware of the testing procedure, you will be able to know whether the relay is in good condition, or is there any problem.
Run a quality check with the following steps-
- Testing coil resistance –
The resistance of the coil is most important as it is important for operating voltage and operating current. So, these two parameters could be calculated as per the resistance of the relay coil which can be tested by the use of a multi meter.
- Testing contact resistance –
Similarly, you can test the contact resistance, which is the resistance of the normally closed contact and a movable contact.
How to check – Turn the multi meter to resistance mode to measure. The resistance mode you get here MUST be zero.
- Resistance being zero, is considered ideal.
- Resistance being unstable or bigger than the value, indicates that the contact is under the condition of poor contact.
- The resistance of the normally open contact and movable contact appearing infinite, the condition shall be normally considered as contact adhesion.
This way, the end users can distinguish which one is normally closed contact, which one is normally open contact and whether the relay is in good condition or not. The method is similar for both new and used relays.
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Testing pull-in voltage and pull-in current
This could be done by connecting the regulated power supply by simultaneously putting a set of voltages to the relay.
Next, connect the ampere meter into the power supply circuit for monitoring.
Slowly turn-up the voltage, and on hearing pull-in sound of the relay, note the pull-in voltage and current.
Repeating the process several times gives an accurate answer.
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Testing release voltage and release current
These are some best ways you can carry out the tests. The process is similar to pull-in voltage and pull-in current testing process.
So when the relay is pulled in, slowly reduce the voltage of power supply.
When hearing the release sound of the relay again, note down the voltage and current.
In general, the release voltage of the relay is 10-50% of the pull-in voltage.
If the release voltage is too low it will have a negative impact on the working of the relay. The relay will not be able to perform normally. Reluctantly, there will be a reduction on the stability of the circuit and reliability of the operation may be susceptible.
There would be many instances where you will need to make use of an electromagnetic relay or replace a relay. For an accurate judgment and proper opinion, you must contact Integra Engineering, one of the best relay manufacturers in India.
The working mechanism of electromagnetic relays is simple to understand. The electromagnetic relay operates largely as per the principle of electromagnetic induction, which also means that as the electric current is passed on the conductor, the conductor behaves like a magnet.
So, as you switch on the power in the low-voltage control circuit, the current goes through the coil of the electromagnet and the coil gets activated by a supply system. Thus, generates a magnetic field.
On this, the armature generates a suction force to connect the movable contact and stationary contact.
The power circuit of the motor switches on and it starts to work.
The process of switching off -
When it comes to switching off the power in the low-voltage control circuit, the current in the coil will disappear, the armature under the action of the spring separates the movable contact and stationary contact.
The working circuit is hence, disconnected and the motor stops working.
The aforementioned process was the switching on and off of the electromagnetic relays. However, the ‘on’ and ‘off’ status relies on electromagnets to control the status of operating circuits.
Usually, when a voltage is generated on both the ends of the coil, the coil gets filled with current and generates an electromagnetic effect.
The electromagnet effect attracts the armature to the iron core against the tension of spring in order to pull the movable contact of the armature to the stationary NO (normally open) contact.
In the process to switch off, the attraction of the electromagnet disappears. Further, the armature gets back to its initial position under tension of the spring to part the movable contact from the stationary contact (normally closed contract or NC).
The pulling and releasing activities are conducted to control a simultaneous opening and closing of the circuit.
And how do you understand if the state is on or off?
You could make out from the state of the stationary contact.
When the coil is cut off from the power, then the stationary contact is the ‘on’ state and the coil is connected to the power if stationery contact is in ‘off’ state.
Electromagnetic relays are the oldest type of relays used in the market. Even after many types of additions in the market, the role of electromagnetic relays is constant.
However, there are also the latest electromagnetic relays coming in the market. For which, you can contact a relay manufacturer in India, to know the latest developments.
Check out our various range of products here:
How to test an electromagnetic relay?
Relay manufacturers in India are experts in testing the EMRs. Once you understand the characteristics and working principles of an electromagnetic relay, it is worth knowing the process of testing an electromagnetic relay. Once you are aware of the testing procedure, you will be able to know whether the relay is in good condition, or is there any problem.
Run a quality check with the following steps-
- Testing coil resistance –The resistance of the coil is most important as it is important for operating voltage and operating current. So, these two parameters could be calculated as per the resistance of the relay coil which can be tested by the use of a multi meter.
- Testing contact resistance –Similarly, you can test the contact resistance, which is the resistance of the normally closed contact and a movable contact.How to check – Turn the multi meter to resistance mode to measure. The resistance mode you get here MUST be zero.
- Resistance being zero, is considered ideal.
- Resistance being unstable or bigger than the value, indicates that the contact is under the condition of poor contact.
- The resistance of the normally open contact and movable contact appearing infinite, the condition shall be normally considered as contact adhesion.
This way, the end users can distinguish which one is normally closed contact, which one is normally open contact and whether the relay is in good condition or not. The method is similar for both new and used relays. - Testing pull-in voltage and pull-in currentThis could be done by connecting the regulated power supply by simultaneously putting a set of voltages to the relay.Next, connect the ampere meter into the power supply circuit for monitoring.Slowly turn-up the voltage, and on hearing pull-in sound of the relay, note the pull-in voltage and current.Repeating the process several times gives an accurate answer.
- Testing release voltage and release currentThese are some best ways you can carry out the tests. The process is similar to pull-in voltage and pull-in current testing process.So when the relay is pulled in, slowly reduce the voltage of power supply.When hearing the release sound of the relay again, note down the voltage and current.In general, the release voltage of the relay is 10-50% of the pull-in voltage.If the release voltage is too low it will have a negative impact on the working of the relay. The relay will not be able to perform normally. Reluctantly, there will be a reduction on the stability of the circuit and reliability of the operation may be susceptible.There would be many instances where you will need to make use of an electromagnetic relay or replace a relay. For an accurate judgment and proper opinion, you must contact Integra Engineering, one of the best relay manufacturers in India.
