How does a bimetallic overload relay work?

How does a bimetallic overload relay work?

Bimetallic Overload Relay These bimetallic strips are heated by a winding around the bimetal strip, which carries the current. Both of the metal strips will expand due to the heat. However, the metal with a high coefficient of expansion will expand more in comparison to the metal with a low coefficient of expansion.

What is bimetallic relay?

Bimetallic thermal overload relays (sometimes referred to as heater elements) are made of two metals, with different coefficients of thermal expansion, that are fastened or bonded together. A winding, wrapped around or placed near the bimetallic strip, carries current.

How does a thermal relay work?

A thermal relay works depending upon the above mentioned property of metals. The basic working principle of thermal relay is that, when a bimetallic strip is heated up by a heating coil carrying over current of the system, it bends and makes normally open contacts.

What is the function of 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 the bimetal how it is used for protecting motors?

Thermal motor protection relays contain three bimetal strips together with a trip mechanism in a housing made of insulating material. The bimetal strips are heated by the motor current, causing them to bend and activating the trip mechanism after a certain travel which depends on the current-setting of the relay.

What are two types of thermal overload relays?

There are two major types of overload relays: thermal and magnetic. Thermal overloads operate by connecting a heater in series with the motor. The amount of heat produced is dependent on motor current. Thermal overloads can be divided into two types: solder melting type, or solder pot, and bimetal strip type.

What causes thermal overload?

Causes may include a large change in load (e.g., a scrap grinder is fed too much at a time), misalignment, a broken drive gear, or improper motor drive settings. Power problems (e.g., low voltage or low power factor) also may cause an overload condition.

What is bimetal how it is used?

Bimetals are used for temperature indication as in the spiral or helix actuated pointer thermometers. Such thermometers help measure temperatures in offices, refrigerators, and even on aircraft wings.

What is a bimetallic?

Definition of bimetallic 1 : relating to, based on, or using bimetallism. 2 : composed of two different metals —often used of devices having a part in which two metals that expand differently are bonded together. Other Words from bimetallic Example Sentences Learn More About bimetallic.

Which relay is used for motor protection?

The EMR-5000 motor protection relay measures the current and voltage unbalance and either can be used to alarm or trip the motor before damage occurs . The EMR-5000 has 2 voltage and 2 current unbalance elements .

How does motor protection relay work?

What are the two major types of thermal overload relays?

How does a bimetal thermal fuse work?

Bimetal thermostats can also be outfitted with a thermal fuse. Designed to detect high heat, the thermal fuse will automatically break the circuit, which can save the device to which it’s attached. Bimetal thermostats come in a variety of sizes and shapes.

What is bimetallic effect?

As many metallurgists will know, the bimetal effect, or bimetallic corrosion as it is sometimes referred to, will only happen when two metals of a dissimilar nature come into what is termed electrical contact with one another and they are bridged by liquid that is electrically conductive.

On what principle does a bimetal strip operate?

of thermal expansion
Definition: A bimetallic strip works on the principle of thermal expansion, which is defined as the change in volume of metal with the change in temperature.

What causes motor overload?

Electrical overload or over-current is caused by an excessive current flow within the motor windings, exceeding the design current which the motor is able to carry efficiently and safely. This can be caused by a low supply voltage, resulting in the motor drawing in more current in an attempt to maintain its torque.

What is a bimetallic overload relay?

The bimetallic overload relay consists of a small heater element wired in series with the motor and a bimetal strip that can be used as a trip level. A bimetal strip is made up of two dissimilar metals permanently joined together.

What is a bimetallic thermostat based relay?

Bimetallic thermostat based relays are used for detecting the over current in electric devices to protect them from over current. The current flowing through circuit or device is passed througha heating coil which heats the bimetallic strip.

What happens to the bimetal when the ambient temperature changes?

As the ambient temperature changes, both bimetal strips will bend equally and the overload relay will not trip the motor. However, current flow through the motor and heater element will affect the primary bimetal strip. In event of an overload condition the primary bimetal strip will engage the trip unit.

What is the working principle of bimetal?

An electrical contact is connected on free end of bimetal, which moves with the expansion and bending of bimetal. At normal temperature, this moving contact makes the contact with fixed contact as shown in figure below.