Transient Analysis of an Electromechanical Relay Using an FEA Tool

Linear and rotational actuators
By Mohamed Watouti | 15/09/2023


Electromagnet relays are essential components in various electrical and electronic systems, serving as switches or amplifiers for controlling circuits. Understanding the transient magnetic behavior of these relays is crucial for their optimal design and performance. Finite Element Analysis (FEA) tools provide a powerful approach to simulate and analyze complex electromagnetic phenomena, including eddy currents, which play a significant role in relay behavior.

Electromagnet Relays: A Brief Overview

Electromagnet relays are essential components used in a wide range of electrical and electronic systems to control circuits, switch loads, and amplify signals. They are widely employed in various applications, from power distribution and industrial automation to telecommunications and consumer electronics.

The basic working principle of an electromagnetic relay involves the interaction between an electromagnet and a mechanical switching mechanism. When an electric current flows through the coil of the relay, it generates a magnetic field. This magnetic field exerts a force on a movable component, often called the armature or core, causing it to move. This mechanical movement then leads to the opening or closing of electrical contacts, thus controlling the flow of current in a separate circuit.

Applications of Electromagnet Relays

The typical application of electromagnet relays include:

  • Power Distribution: Relays are used in power distribution systems to control the flow of electricity and protect against overloads and short circuits.
  • Industrial Automation: They are integral in controlling motors, pumps, solenoids, and other machinery in manufacturing and industrial processes.
  • Automotive Systems: Relays are used in automotive applications for functions like starting, lighting, wipers, and more.
  • Telecommunications: They play a role in signal routing and switching in communication networks.
  • Consumer Electronics: Relays are used in household appliances, HVAC systems, and entertainment devices.
  • Safety Systems: In safety-critical applications, relays are used to trigger alarms, shutdown systems, and control emergency protocols.
  • Aerospace and Defense: They are employed in avionics, missile systems, and various defense applications.

Role of Eddy Currents in Electromagnet Relays

Eddy currents are circulating currents induced in conductive materials when exposed to changing magnetic fields. Eddy currents play a significant and multifaceted role in the behavior and performance of electromagnet relays. These circulating currents, induced by changing magnetic fields in conductive materials, have both advantageous and detrimental effects on relay operation. Understanding their role is crucial for designing efficient and reliable relay systems. Here's a closer look at the role of eddy currents in electromagnet relays.

Joule Heating

Eddy currents encounter resistance as they flow through conductive materials, leading to Joule heating. This phenomenon can impact relay performance in the following ways:

Temperature Rise: Eddy currents generate heat due to their resistance. In relay components like the core and surrounding metal structures, excessive heat can lead to temperature rise, potentially affecting the relay's functionality and lifespan. Designers must consider thermal management strategies to ensure reliable operation.

Material Consideration: The choice of materials with lower electrical resistivity can help reduce eddy current losses and subsequent heating effects. Soft magnetic materials, which exhibit lower electrical resistivity, are often preferred for the core to minimize these losses.

Electromagnetic Damping

Eddy currents create opposing magnetic fields that interact with the relay's intended magnetic fields. This interaction introduces a damping effect on the relay's mechanical motion. The role of electromagnetic damping includes:

Mechanical Response: Electromagnetic damping influences the mechanical movement of the relay's components. While some level of damping can be beneficial to achieve controlled and smooth relay operation, excessive damping can lead to slower response times and reduced efficiency.

Response Time Optimization: Designers must strike a balance between minimizing damping for quicker response times and maintaining enough damping to prevent mechanical oscillations or "bouncing" of relay contacts during operation.

Impact on Efficiency

Eddy currents, while often considered losses due to the associated Joule heating, can also have a positive impact on relay efficiency:

Reduced Vibrations: The damping effect of eddy currents can help reduce mechanical vibrations and oscillations in the relay's moving components. This results in quieter operation and reduced wear and tear on relay contacts.

Stable Operation: Controlled damping from eddy currents can contribute to stable relay operation by preventing overshooting or bouncing of contacts during opening or closing.

Design Considerations

Engineers and designers need to account for the role of eddy currents during the design phase of electromagnet relays:

Geometry and Materials: Optimizing the relay's core geometry, as well as selecting materials with appropriate electrical and magnetic properties, can help mitigate the adverse effects of eddy currents.

Coil Design: Designing the coil for efficient energy conversion and distribution of magnetic fields can minimize eddy current losses. Coil geometry and the use of insulating materials between winding layers are crucial considerations.

Dynamic Performance: Simulating relay behavior using electromagnetic FEA tools enables designers to visualize the effects of eddy currents during transient states, aiding in optimizing dynamic performance.

Design Solutions for Electromagnet relay by EMWorks

EMWorks provides a suite of powerful simulation tools that can be used for the design and modeling of Electromagnet relays. EMS for SOLIDWORKS is a 3D FEA tool that allow users to accurately simulate the performance and optimize their design, leading to improved efficiency and performance. One of the key capabilities of EMS is its ability to accurately model electromagnetic fields. This is essential for the design of Electromagnet relays, as these devices rely on magnetic fields to generate motion. In addition to these core capabilities, ES also offers a range of advanced features for optimizing the design of Electromagnet relays. For example, users can simulate the effects of different materials and geometries, evaluate the performance of different coil designs, and optimize the control strategy for the relay.

Transient Magnetic Analysis using EMS for SOLIDWORKS

Transient magnetic analysis involves studying the magnetic behavior of a system as it changes over time. EMS for SOLIDWORKS provides a virtual platform for modeling and analyzing these time-dependent behaviors. These tools employ numerical methods to solve complex differential equations governing electromagnetic fields and forces.

The Electromagnet relay is mainly composed of the following components:

  • Coil: The coil is a wound wire that carries the control current. When energized, it generates a magnetic field.
  • Moving Armature: The movable component within the relay that responds to the magnetic field generated by the coil. It is responsible for opening or closing the electrical contacts.
  • Contacts (not included in this simulation): These are metal plates that make or break electrical connections when the core moves. Contacts are designed to handle different levels of current and voltage, depending on the relay's application.
  • Spring: A spring is often used to provide the necessary mechanical force to return the armature to its original position when the coil is de-energized.

Figure 1 shows the 3D model of the electromagnet relay simulated inside EMS for SOLIDWORKS.

Fig. 1. 3D Model of the Simulated Electromagnetic Relay

Finite Element Analysis (FEA) simulations of electromagnet relays provide a wealth of valuable output results that offer insights into the relay's behavior, performance, and interactions between different components. These results aid in optimizing the relay's design, identifying potential issues, and ensuring its efficient and reliable operation.

Here are the main output results that can be interpreted after an FEA simulation of an electromagnet relay:

Attraction force in the movable core

The attraction force in the movable core of an electromagnet relay is a critical parameter that directly influences the relay's operation and performance. It is the force exerted on the movable core or armature of the relay due to the electromagnetic field generated by the coil. This force determines the movement of the core, which in turn affects the opening or closing of the relay's contacts. Understanding and accurately predicting the attraction force is essential for designing relays that function reliably and efficiently. Figure 2 shows the attraction force in the movable core.

Fig. 2. Attraction Force in the Movable Core

Magnetic Field Distribution

EMS provides a visual representation of the magnetic field distribution within and around the relay's components. This output helps identify areas of high and low magnetic flux density, which are crucial for understanding how the magnetic circuit is established and whether the intended magnetic paths are being followed. Figure 3 shows the animation of the magnetic Field inside the electromagnet relay.