Relay Basics: Technology

Types of Coils

Coils are classified according to the types of magnetic circuits and operational functions.

1. Magnetic circuit

Non-polarized: Operating coils do not have polarity
Polarized: Operating coils have polarity

2. Basic Function

Relay is classified into two basic functions: single-side stable relay and latching relay (also called "Keep" relay)

Single-Side Stable Relay

The contacts turn ON or OFF only when an input signal is received.

Latching (Keep) Relay

The contacts turn ON or OFF when an input signal is received but maintains its contact position during power interruptions.

Select the optimal relay that meets your application and sequence requirements.

Types of Contacts for Electrical Relays

Contacts are classified according to the types of contact forms and contact reliabilities.

1. Contact Forms

There are three types of contact forms: Form A contacts, Form B contacts, and Form C contacts.

Form A contacts ("Make contacts")

This is normally open contact and closes when a voltage is applied to the coil.

Form B contacts ("Break contacts")

This is normally closed contact and opens when a voltage is applied to the coil.

Form C contacts ("Transfer contacts")

Combines the Form A and Form B contacts in a single relay and when a voltage is applied to the coil, Form C contact moves away from Form B contact and connects with Form A contact (for single-side stable relays).

2. Electrical Relay Contact Reliability

Contact configurations are classified into three types according to the reliability level: Single contact, Twin contact and Cross-bar Twin contact.

Types of Terminals for Electrical Relays

The terminal configurations are classified as follows:

Types of Terminal	Terminal configuration	Typical Relay Model
Plug-in terminal	on maintenance,Lineup of dedicated sockets	MY
PC board terminal	PC board (through hole) mount type	G5NB
Screw terminal	Emphasis on maintenance,Screw terminal connection	G7Z
Surface-mount terminal	PC board (surface-mount) automatic mount type	G6K(-F/G)
Quick connect terminal	Emphasis on maintenance,Tab terminal connection	G2R-T

Enclosures for Electrical Relays

The terminal configurations are classified as follows:

× : Penetration exist
○ : No penetration
△ : Penetration may exist

Enclosures	Characteristics	Atmosphere Conditions		Typical Relay Models
Enclosures	Characteristics	Dust and dirt	Harmful gas	Typical Relay Models
Flux resistant type(PCB relay)	This type of structure prevents solder flux penetration into the interior.	△(Protects from large amounts of dirt and dust)	×	G2R
Palstic Sealed(PCB Relay)	This type of structure prevents solder flux and cleaning solvent penetration.	○	○	G5Q
Unsealed(Plug-in Relay)	This type of structure places the relay inside a case to protect against foreign substances.	△	×	MY
Plastic Sealed(Plug-in relay)	This type of structure places the relay with resin case and cover to minimize corrosion effects.	○	○	MYQ
Hermetically sealed(Plug-in relay)	This type of structure places the relay in a corrosion resistant sealed case using metal or glass purged with inert gas (N2) to protect from corrosive gas penetration.	○	○	MYH