Types of Overload Relay Components

Overload relays protect motors from problems that can cause heat damage. They are connected in series with the motor and are designed to trip when a specific current rises. This causes the circuit to open between the power source and the motor. The relay can be manually or automatically reset after a predetermined duration.

Thermocouple

A thermocouple consists of two different types of metal wires that are joined together to form a temperature measuring junction. The differences in the metals cause electrons to move differently when they are exposed to heat. This creates an electromotive force (EMF) that is measured in millivolts. The EMF is then projected as a temperature reading. The thermocouple is used to measure temperature in many applications, including industrial processes.

Thermocouples are used in motor circuits to protect them from overheating and tripping the relay switch. The current flowing through the motor passes through the bimetallic tripping element and causes it to bend. When the electrical coil reaches a certain temperature, it triggers the relay to open and shut down the circuit. The time it takes for the relay to cool down and reset depends on a number of factors, including ambient temperature and air flow.

Thermocouple sensors are available in a wide range of types and configurations to suit different environments and uses. To choose the right thermocouple for your application, first consider what the maximum and minimum temperature ranges are. You also need to know the expected usable sensor lifespan and whether the environment will be oxidizing or inert. Once you have these answers, refer to the Thermocouple Types table to select a suitable sensor. There are also extension wires that allow you to extend the signal of a thermocouple and connect it to instrumentation. These are typically marked ’KX’ or ‘JX’ and are designed to work at lower temperatures than the thermocouple itself.

Bimetallic strip

This is a device that converts a temperature change into mechanical displacement. It works by bonding two strips of dissimilar metals with different thermal expansion coefficients together and then heating them. As they warm up, one of the strips expands faster than the other, causing the strip to bend. It is then switched off when it cools down. This type of sensor is used in a variety of electrical and mechanical devices, including overload relays.

Overload relays are a popular form of heat-sensitive switch. They are designed to open when the current flows through isolated gate driver them exceeds a set limit, such as the maximum temperature rise in a motor. They are available in both electromechanical and solid state models. Solid-state relays are less expensive than their electromechanical counterparts and offer the added advantage of being able to operate in explosive environments.

A bimetallic strip is an essential component of an overload relay. It combines two strips of metal with different expansion characteristics and is attached to a pair of normally closed contacts. When it is heated, the bimetallic strip bends and operates a set of spring-loaded contacts to interrupt the current flow. This type of relay is often used in small circuit breakers to protect motors from overcurrent.

In the case of an overload condition, Quadrant Divider and Multiplier the eutectic alloy tube in a bimetallic relay is heated by the heater winding and triggers a series of contact closures to prevent current from flowing to the coils that activate the overload mechanism. This is a safety feature that gives an operator time to determine the cause of the overload without jeopardizing the motor or exposing them to injury.

Contactor

A contactor is a large relay used to switch current to an electric motor or other high-power load. It also protects the motor from overcurrent damage by monitoring the current flow through the circuit. Overload relays contain overload heaters and overload contacts that operate when the current exceeds a set limit. Some types of overload relays use Hall effect sensors or current transformers to detect the sum of current flowing through the circuit. These relays do not require a bimetallic strip and can be considered solid-state relays.

Overload relays are usually wired in series with the motor. This means that the current that flows to the motor must first pass through the overload relay. If the current reaches an excessive level, the overload relay will trip, which opens the circuit between the power source and the motor. The relay can be manually or automatically reset after a predetermined time period.

Overload relays can be divided into different classes according to their tripping times. The tripping time of the relay depends on the temperature of the bimetallic strip, which can be measured with a thermocouple. It is important to understand the working of the thermal-type overload relay so that you can properly use it.

Reset button

The reset button is an important feature in many electronic based devices/ systems. It is used to restart the device in case of any error or power loss. It is also a feature in some smart devices like smartphones. There are two types of reset buttons – soft and hard. A soft reset is a more controlled and graceful way of restarting the device, allowing ongoing processes to terminate properly. A hard reset is a more forceful way of restarting the device, often performed through hardware buttons or switches.

The overload protection relay protects the motor against problems like overheating by switching off the circuit between the power supply and the motor. When the relay senses that there is a problem, it trips at a predetermined level and breaks contact. It can be manually or automatically reset after a specified period of time.

These thermal overload relays are primarily designed to mimic a heating prototype of an electric motor and can be used in both 1 and 3 phase electrical motors. Some of these relays are even designed to ensure protection from internal phase losses. They also come with rotary knobs for adjusting the rated current. In addition, they come with internal trip class selection buttons for easy operations. Moreover, they are highly durable and long-lasting, making them an ideal choice for commercial use.