MAGNETIC MATERIALS
FOR RELAYS
KRISHNA JYOTHI NADELLA
Magnetic Materials for Relays
Relay: A relay is an electrically operated switch . Many relays use an electromagnet to operate a switching mechanism. Relays are used where it is necessary to control a circuit by a low power signal or where several circuits must be controlled by one signal.
Relays were used extensively in telephone exchanges and early computers to perform logical operations.
Relays
Simple electromagnetic relay
Different types of relays
New magnetic materials for relay designes
Ceramic Magnets
1) They are the least expensive magnets.
2) They are very resistant to corrosion.
3) They are stable up to approximately 300°C.
1) They are difficult to machine.
2) They have a low energy product (3MGOe).
3) They have a low/moderate coercivity (2KOe).
Alnico Types
1) They are relatively inexpensive.
2) They are stable up to very high temperatures (550°C).
3) They are very resistant to corrosion.
1) They are very difficult to machine.
2) They have a low coercively (1KOe).
3) They have a moderate energy product (5MGOe).
Samarium-Cobalt family
Advantages: 1. Very high energy product
(30MGOe)
2. Very high coercivity (10KOe)
3. Stable at high temperatures
(3500C)
4. They are very resistant to
corrosion .
Disadvantages: 1. They are most expensive
2. They are difficult to machine.
Samarium-Cobalt family
Neodymium-Iron-Boron magnet:
2. High coercivity (15KOe)
3. Relatively easy to machine
4. They are relatively inexpensive.
2. They are not stable above 1500C.
Future developments
MAGNETIC MATERIALS
FOR SENSORS
Magnetic materials for Sensors
Sensor: Sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument.
Ex: 1. Mercury in glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube.
2. A thermocouple converts temperature to an output voltage which can be read by a voltmeter.
Applications of sensors
Permanent magnetic materials for sensors
Specifications of Sensor
Sensors
Definition: a device for sensing a physical variable of a physical system or an environment
Classification of Sensors
Magnets can be used to sense