Electromagnetic relays are those relays which are operated by electromagnetic action. Modern electrical protection relays are mainly micro processor based, but still electromagnetic relay holds its place. It will take much longer time to be replaced the all electromagnetic relays by micro processor based static relays. So before going through detail of protection relay system. we should review the various types of electromagnetic relays.
Electromagnetic Relay Working
Practically all the relaying device are based on either one or more of the following types of electromagnetic relays.
1. Magnitude measurement, 2. Comparison, 3. Ratio measurement.
Principle of electromagnetic relay working is on some basic principles. Depending upon working principle the these can be divided into following types of electromagnetic relays.
1. Attracted Armature type relay, 2. Induction Disc type relay, 3. Induction Cup type relay, 4. Balanced Beam type relay, 5. Moving coil type relay, 6. Polarized Moving Iron type relay.