Electronic Overload Relays IEC

More Information about Electronic Overload Relays

Electronic overload relays are advanced devices used in motor control circuits to provide reliable motor protection against excessive heat and overloads. These relays utilize electronic components and technology to monitor the motor's current flow and detect abnormal conditions. Here are some key aspects and features associated with electronic overload relays:

Motor Protection

Electronic overload relays are designed to protect electrical motors from various types of faults, including overloads, phase loss, and excessive heat. By continuously monitoring the motor current, these relays can detect abnormal conditions that could potentially harm the motor.

Trip Function

When the electronic overload relay detects an abnormal current condition, it initiates a trip function to interrupt the power supply to the motor. This helps prevent damage to the motor and ensures safe operation.

Reset Options

Electronic overload relays offer different reset options. Some relays reset automatically once the abnormal condition is resolved and the motor current returns to normal. Others are reset manually by an operator after troubleshooting and resolving the underlying issue.

Trip Class

Electronic overload relays often come with selectable trip classes, allowing users to set specific response times based on the motor's characteristics and the desired level of protection. Trip classes determine how quickly the relay will trip in response to an overload condition.

Compact Design

These relays are typically designed as single compact devices that combine motor protection functions in one unit. They are often integrated with other motor control components such as contactors and control circuitry.

Communication Capabilities

Some electronic overload relays feature communication capabilities, allowing them to integrate with control systems and provide real-time monitoring and diagnostics. This enables remote monitoring and enhanced system management.

Installation and Wiring

Electronic overload relays come with clear installation instructions to ensure proper integration into the motor control circuit. They are wired in series with the motor starter and may require additional connections to an auxiliary contact or control devices.

Suitable for Industrial Applications

Electronic overload relays are widely used in various industrial applications where precise and reliable motor protection is required. They are compatible with three-phase motor systems and suitable for a range of motor sizes and types.

Temperature and Life Monitoring

Some advanced electronic overload relays incorporate features for monitoring temperature and motor operating conditions. This information can be used for preventive maintenance and optimizing motor performance.

Reliable Protection

Electronic overload relays offer accurate and reliable motor protection, helping to prevent costly motor damage, downtime, and potential safety hazards. Their electronic components and thermal modeling ensure effective operation and consistent performance.

Motor Control Basics

Motor control allows operational control of electrical motors in various environments. 

Motor control circuits provide a safe way to operate electrical motors. Back when motor control circuits were in their infancy, it would have been common to see a simple disconnect switch that would be used to turn on and off a motor. Depending on the size of the motor and how much voltage was required, operating this disconnect would have been dangerous, with a very high possibility of arcing or electrocution. Not to mention that when the disconnect was actuated, the large amount of inrush current would have damaged the motor over time.

In today's motor control circuits, there are a few common pieces of hardware. 

A circuit breaker is used to protect the motor and any hardware downstream. A contactor and an overload relay are connected together and function in tandem to allow for remote and safe operation of the motor. The contactor functions much like a relay, allowing for a smaller electrical circuit to remotely close the motor contacts, starting the motor. The overload relay is designed to protect the motor in the case of a prolonged overcurrent event. These two devices are wired in series, so that if the overload relay detects an overcurrent event, the contactor will open the motor contacts, shutting off power to the motor.

The other two most common types of motor control hardware are a soft starter and a Variable Frequency Drive (VFD). 

Both of these devices function in a similar way to the motor circuit with some added functions. The soft starter is designed to reduce large inrush current to the motor upon startup. This “soft starting” of the motor will prolong its life and allow for safer operation. The VFD performs the soft start functions, but also allows for speed control of the motor. This speed control is critical in many different environments and has made VFDs one of the most common and safe to use motor control circuits today.