electromagnetic relay. description electrically controlled switch current through coil magnetises...
TRANSCRIPT
Electromagnetic relay
Description
• Electrically controlled switch• Current through coil• Magnetises soft iron core• Soft iron armature moves• Contacts join
Normally Open [NO] Relay
• No current flowing through the coil • Contacts are not made• Coil must be energised for switched circuit to work
Normally Closed [NC] Relay
• No current flowing through the coil • Contacts are made• Coil must be energised for switched circuit to stop working
In a circuit
• Low current flows through coil
• Attracts armature• Switched circuit connected• Lamp lights• BUT Coil is an inductive load
– Add protection diode– Prevent high voltage
spike
dt
dILV
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• Reed relay• Electromagnetic relay• Magnetic switch