What is a Relay - Jim Asks
Top three images -
Smart Contactors. Timer, Thermostat. Over Current or Voltage. Trip or Limit. Three Phase Trip. High Power. Solenoid hammer.
Power Contactors. High Power. Nut-Bolt Mounting. Solenoid hammer. Special Contacts. Special Plastics. Heaters and Motors.
Din Rail Contactors. High Power. Easy Replace Rail Mount. Solenoid hammer. Heaters and Motors. Modular, Stackable. SCADA, Control Panels.
Bottom Three images - Relays are much smaller, they are power switching relays and signal switching relays. They are mounted on PCBs or on cabinets/enclosures.
Then we have power relays, like the three above. They may be mounted on PCBs or Inside the Cabinets. They switch currents upto 5 Amps and voltages upto 230V. These are used in Home Automation and in Instruments. The Signal from these drive Contactors in Large Power Systems.
The PCB Versions should not be used for high currents, use for signalling contacters or driving Lamps and Hooters in Annunciation and Alarm systems.
Medium Power. Solder Terminations. Panel Mount. Solenoid hammer. Low Cost. Time Tested Design. Commercial.
Low Power DPDT. PCB Mount. Solenoid hammer. Visual Isolation. Switches Two Loads. Industrial.
Low Power. Small Footprint. Solenoid hammer. Communications. Appliance Control. Low Cost.
In image below - see top three images
Medium Power. Panel or Rail Base Mount. Solenoid hammer. Visual Isolation. Easy Replace, Plugin. Industrial.
Medium Power. PCB Mount. Solenoid hammer. Visual Isolation. Switches Two Circuits. Industrial.
Low Power SPDT. PCB Mount. Solenoid hammer. Visual Isolation. Controls Contactor. Industrial.
Bottom three images are Analog or Digital Signal Relays, means very low current, Low voltage. It is used in Instrumentation, Communications and circuit multiplexing.
Micro Power. Telecommunications. Analog Signal Switch. Low Capacitance. Low Inductance. Reed Relay.
Micro Power. Analog Signal Switch. Small Footprint. Reed Relay. Instrumentation. Communications.
Micro Power. Analog Signal Switch. Small Footprint. Reed Relay. Communications. Low Ripple Pickup.
Choosing a relay- A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts.
Relay Timing - The text covers electronic circuit to sequence and speed separate relays (like dual vacuum relays) and describes how to sequence mechanically ganged contacts like those in open frame relays.
Relay - Wikipedia - A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts,