What is OL in motor control?

The letters often represent the type of device, such as M for motor starter, CR for control relay, OL for overload relay or TR for timing relay.

How does a motor overload relay work?

The overload relay is wired in series with the motor, so the current that flows to the motor when the motor is operating also flows through the overload relay. It will trip at a certain level when there is excess current flowing through it. This causes the circuit between the motor and the power source to open.

What is the function thermal overload relay?

Thermal overload relays are economic electromechanical protection devices for the main circuit. They offer reliable protection for motors in the event of overload or phase failure. The thermal overload relay can make up a compact starting solution together with contactors.

What is a solid-state overload relay?

Solid-State x Thermal (Bimetallic) Overload Relays Thermal overload relays are designed to mimic the heat actually generated in the motor. In solid-state overload relays, the motor current is measured by current transformers and then converted into an electronic signal.

Why contactors are used?

A contactor is an electrical device which is used for switching an electrical circuit on or off. These contacts are in most cases normally open and provide operating power to the load when the contactor coil is energized. Contactors are most commonly used for controlling electric motors.

What is a seal in relay?

The Seal-in relay is energized by the Sudden Pressure Relay micro switch; its purpose is to close alarm and/or trip circuits and seal itself closed until manually reset by the reset pushbutton.

What are 2 types of overload relays?

Overload Relay Types. These are classified into two types namely thermal overload relay and magnetic overload relay.

What is contactor and relay?

Contactors and Control relays are electrically operated switches used for switching of loads and for controlling the electrical circuit respectively. Contactor and Control Relay work on same principle. They are basically electrically operated solenoid switches that are designed for the switching or control the loads.

What relay is used in mercury?

mercury displacement relay
A mercury relay (mercury displacement relay, mercury contactor) is a relay that uses mercury as the switching element. They are used as high-current switches or contactors, where contact erosion from constant cycling would be a problem for conventional relay contacts.

What is a thermal relay?

A relay that opens or closes contacts with a bending mechanism as a result of the difference in the expansion coefficients of a bimetal, which is heated by the current. The thermal relay switches a magnetic contactor to protect a motor from overload.

What are DC contactors?

A DC contactor is an electrically controlled device designed to switch current on and off. DC contactors control current in DC circuits by closing and opening internal contacts. DC contactors control much lower voltages than AC circuits and offer the benefit of minimal arcing as the circuit opens and closes.

What is difference between contactor and relay?

Control Relay: It is a device through which contacts in one circuit are operated by an alteration in conditions in the same circuit or in associated circuits. Contactor: It is a device which is used for repeatedly establishing and interrupting an electric circuit under normal conditions.

What is a so relay?

So relay is a switch which controls (open and close) circuits electromechanically. The main operation of this device is to make or break contact with the help of a signal without any human involvement in order to switch it ON or OFF.

What is a relay in Electrical Engineering?

Electrical Relay Definition Relays are electrically operated switches that open and close the circuits by receiving electrical signals from outside sources. Some people may associate “relay” with a racing competition where members of the team take turns passing batons to complete the race.

What are the parts of a contact relay?

Contact Arrangement:The combination of contact forms that make up the entire relay switching structure. Contact Housing:The part that provides means for mounting fixed contacts on a supporting structure. Contact Material:Substance or combination of substances used as constituents in the manufacture of the contacts.

What is a MOS FET relay?

The combination of fixed and movable contacts opens and closes the control circuit. One of the major characteristics of a MOS FET relay is that it utilizes semiconductor so the contacts do not mechanically open/close.