What is an Conventional Electromechanical Relay?
A conventional electromechanical relay is an electromechanical Relay that manages circuits between 6 and 16 A.
Although you can find a more detailed explanation of relays and electromechanical relays on our Relays page, due to their importance we detail the important parameters to take into account when choosing them.
What are the main parameters of a relay?
The parameters of a relay are:
Determine basic issues as with any object: size, weight and physical shape:
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Length.
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Broad.
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Height.
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Diameter.
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Weight.
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Physical form.
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Parameters of a relay depending on its contacts and circuits
It is the maximum current that the relay can withstand safely and without being damaged when opening and closing its contacts.
Defines the configuration of the circuits, relay poles and throws and its behavior. The basic information are:
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- The pole is the input of the circuit breaker.
- The number of poles will define the number of individual circuits that the relay can manage.
- The throws that each relay circuit has.
The contact forms of a relay are defined by:
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- Format : The configuration of the relay based on its poles, circuits and outputs.
Its encoding is determined using the following format:
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- (Number of poles) P (Number of throws) T
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- The number of poles and throwscan 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:
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- SPST (Single Pole Single Throw): It is the simplest, a switch with 1 input and 1 throw.
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- SPDT (Single Pole Double Throw): It is a switch with 1 input and 2 throws.
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- DPDT (Double Pole Doble Throw): 2 poles and therefore 2 circuits, 2 throws per circuit.
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- 3PDT (3 Poles Doble Throw): 3 poles and therefore 3 circuits, 2 throws per circuit.
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- 4PDT (4 Poles Doble Throw): 4 poles and therefore 4 circuits, 2 throws per circuit.
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- Form: Defines the behavior of the relay circuits when it is stopped and when it comes into operation. The magnetic field is generated by the relay coil after applying its working voltage, or by an external magnetic field in Reeds relays.
Its encoding is determined using the following format:
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- [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:
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- A: NO - Normally Open Contacts when the relay coil is stopped or de-energized, or when there is no nearby magnetic field in the case of Reed relays.
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- B: NC - Normally Closed Contacts when the relay coil is stopped or de-energized, or when there is no nearby magnetic field in the case of Reed relays.
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- C: Contacts Normally Open in one circuit and Normally Closed in another when the relay coil is stopped or de-energized, or when there is no nearby magnetic field in the case of Reed relays.
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- In type C, at the moment of the coil's ignitioning, the circuit that is Normally Closed when is stopped or de-energized then will become open, and then once the start of ignition time has elapsed, the circuit did not change its state and was open, it will be closed.
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- Form C guarantees that for an instant, all contacts are open (BBM - Break-Before-Make).
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- D: It is similar to Form C except for the behavior of the ignition time. In Form C, at the moment the coil starts to work, all the contacts will be closed. (MBB - Make-Before-Make).
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Parameters in relation with relay coil
It is the nominal voltage at which the coil is designed to operate.
Minimum voltage determined by the manufacturer, and is the one 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.
Maximum voltage determined by the manufacturer, which can be applied to the coil in the usual way without being damaged.
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Voltage type or current type
Type of voltage that can be applied to activate the relay:
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- Vac: Designed for alternating current.
- Vdc: Designed for direct current.
- Vac / Vdc: Designed for operation in both alternating current and direct current.
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Coil resistance
The internal resistance of the coil.
It refers to the coil consumption.