What are electromechanical relays?
These relays are essential devices in numerous electrical and industrial applications due to their ability to control the flow of current through an electromagnetic mechanism. Before delving into the details, it is important to understand the key parameters that define its performance, that is, what are the main parameters of an electromechanical relay.
Physical parameters of conventional electromechanical relays
These products are essential in the switching of electrical circuits and their operation is based on a combination of physical and electromagnetic components. Exploring its physical parameters allows us to better understand its design and operation in industrial and electronic applications.
Physical dimensions (Length, Width, Height, Diameter and Shape)
It is a crucial role in the design and operation within electrical and electronic systems. In short, they are important for four main reasons:
- Mounting Space: May affect the ease of installation and the space required on the electrical panel or device.
- Mechanical Compatibility: The physical dimensions of conventional electromechanical relays must be adequate to fit correctly into the available space and to ensure that contacts and connections are correctly aligned.
- Heat dissipation: They can affect the heat dissipation capacity and therefore its suitability to operate efficiently and reliably, especially in high power or high current applications.
- Mechanical stability: They can guarantee stability and durability, avoiding possible vibrations or unwanted movements that could affect its operation.
Weight
Considering the impact on performance and handling, it is crucial to understand its importance in several aspects:
- Handling and Transportation: Weight may affect ease of handling during installation and transportation. A lighter conventional electromechanical relay may be easier to handle.
- Load capacity: It can indicate its load capacity and robustness. Heavier devices are often designed to handle higher currents and offer greater durability in demanding industrial applications.
- Structural stability: Proper weight can contribute to your structural stability within the electrical system.
Parameters of a conventional electromechanical relay depending on its contacts and circuits
The configuration of the contacts and internal circuits is essential to define their operating characteristics. The parameters to take into account are the following:
Current
It is the maximum current that the electromagnetic device can withstand safely and without being damaged when opening and closing its contacts. Selecting a conventional electromechanical relay with an appropriate current rating is essential to ensure optimal performance.
Contact forms
Defines the configuration of the circuits, poles, relay outputs as well as its behavior. The basic data is as follows:
- Pole: It is the input of the circuit switch.
- Number of poles: Defines the number of individual circuits that the device can manage.
- Throws from each relay circuit.
Instead, the contact forms of a relay are defined by:
Shape
The configuration of the relay based on its poles, circuits and outputs. Its coding is determined using the following format: P (Number of Poles) and T (Number of Throws).
By other hand, the number of poles and outputs can be defined with a letter or a number: S (Single or 1 pole), D (Double or 2 poles), 3 (3 poles) and so on. The most common classifications are:
- SPST (Single Pole Single Throw): It is the simplest, a switch with 1 input and 1 output.
- SPDT (Single Pole Double Throw): It is a switch, 1 input and 2 outputs.
- DPDT (Double Pole Double Throw): 2 poles and therefore 2 circuits, 2 outputs per circuit.
- 3PDT (3 Poles Double Throw): 3 poles and therefore 3 circuits, 2 outputs per circuit.
- 4PDT (4 Poles Double Throw): 4 poles and therefore 4 circuits, 2 outputs per circuit.
Shape
Defines the behavior of the conventional electromechanical relay circuits when it is at rest and when it comes into operation. It is not important whether the magnetic field is generated by the coil after applying its working voltage or, in the case of Reed switches, by bringing a magnetic field close to the bulb.
Its coding is determined using the following format: [Number of poles] Form (x). The number of poles is an optional data depending on the manufacturer. If the information has been included in the form, the number of poles may not be included in the form. The defined forms are:
- A: Normally Open Contacts (NO - NO Normally Open) when the coil is at rest, or when there is no nearby magnetic field in the case of Reeds ampoules.
- B: Normally Closed Contacts (NC - NC Normally Closed) when the relay coil is at rest, or when there is no nearby magnetic field in the case of Reeds bulbs.
- C: Contacts Normally Open in one circuit and Normally Closed in another when the relay coil is at rest, or when there is no nearby magnetic field in the case of Reeds bulbs. In type C, at the moment the coil starts acting, the circuit that is Normally Closed at rest will become open. Next, once the start time has expired, the one that did not change its status and was open will become closed. Form C guarantees that, for a moment, all contacts are open (BBM - Break-Before-Make).
- D: It is similar to Form C except for the behavior of the instant of action. In Form C, at the moment the coil starts acting, all the circuit contacts will be closed (MBB - Make-Before-Make).
Parameters related to a relay coil
These parameters are crucial roles in the operation and performance of various electrical applications. The configuration and characteristics of the coil are fundamental elements that influence its activation capacity, power consumption and compatibility with different operating voltages and frequencies. Below are the most relevant ones:
Working voltage
It is the nominal voltage at which the coil is designed to operate. Ensuring that the working voltage is adequate is essential to avoid possible risks of short circuits, overloads or failures in the electrical circuit. An incorrect voltage could compromise the integrity of the electrical system as a whole and endanger the safety of equipment and users.
Minimum voltage
It is determined by the manufacturer and is required for the electromagnet to start operating due to the magnetic effect generated by the coil, without altering other parameters such as the activation time. Too low a minimum voltage can cause erratic operation of the conventional electromechanical relay or even its complete failure. It must be compatible with the voltage available in the circuit in which it will be used
Maximum tension
Determined by the manufacturer, it is the voltage that can be applied to the coil on a regular basis without damage. Insufficient maximum voltage can cause the relay to overload, which could result in excessive heating, premature degradation, or even device failure. It is important to ensure that it is high enough to avoid any risk of overloading under normal operating conditions.
Voltage type or current type
It is important to choose the type of voltage that can be applied to activate the relay. It is possible to choose between the following typologies:
- Vac: Designed for alternating current.
- Vdc: Designed for direct current.
- Vac / Vdc: Designed for operation in both alternating current and direct current.
Coil resistance
It is a critical parameter that influences its efficient activation, electrical compatibility and power consumption, ensuring optimal and reliable performance in a variety of electrical and electronic applications.
Power
It is a crucial factor that ensures its switching capacity, electrical compatibility and durability in a variety of electrical and electronic applications. It is important to select a relay with adequate power to ensure optimal performance and safe operation of the system in which it will be used.