Relays

Relays have a wide range of application in industry.Even with the advent of electronic control such as PLC and other solid state devices such as thyristors,the electromechanical relay still retain a high level of acceptance.

We can found relay in every where such as control panel,equipment and machinery.It is common use for automation and motor control application.

The reason for this is that for simple types of control,relay offer a cost effective solution.They are available in a large range of configurations from small of only 10mm in length with multiple contact pair for data communication,to large relay called contactor for carrying heavy current loads in applications such as switching 3 phase motors.

 

Introduction for relay

A relay has certain characteristics :

1) Low maintenance

2) Able to switch a number of independent circuit paths

3) Easy adaptable to various operating voltages

4) High operating speed ( short switching times )

A small amount of energy applied to the relay coil can control a larger energy flow through the relay contact.In the control panel,relay are generally used as signal processor.

Rather than switch solenoid directly via limit switches and potentially overloading current,the relay contacts act as a buffer,carrying the larger amout of current.Another important function of the relay in circuity is as a logic or interlocking device.

Relays operation

 

When voltage is applied to the coil (5),an electric current flow through the winding,a magnetic field builds up and pulls the armature (3) against the core (7) of the coil.The armature is mechanically joined the contact (1) and is pulled against the contact (4).It have 2 types of contact; Normally OPEN and Normally CLOSE.

This switching position is maintained as long as the voltage is applied.When the voltage is removed,the armature is restored to the original position by a spring (6) in the initial position the contact (2) is active.

Coil ratings

Now in market,it have a various coil rating for relays. They have in Alternating current ( AC ) and Direct current ( DC ) voltages.Here i`m list a voltage rating available in market :

Alternating Current ( AC ) ~ 50 /60 Hz

• 6 v
• 12 v
• 48 / 50 v
• 110 / 12o v
• 220 / 240 v

Direct current ( DC )

• 6 v
• 12 v
• 24 v
• 100 / 110 v

Note:

1. The rated current and coil resistance are measured at a coil temperature of 23°C with tolerances of +15%/–20% for rated currents and ±15% for DC coil resistance.
2. Performance characteristic data are measured at a coil temperature of 23°C.
3. AC coil resistance and impedance are provided as reference values (at 60 Hz).
4. Power consumption drop was measured for the above data. When driving transistors, check leakage current and connect a bleeder resistor if required.
5. Rated voltage denoted by “*” will be manufactured upon request.

For more details, please visit relay manufacture website or refer products catalog.