Actuator Third Coil for 8/20µs Immunity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electromagnetic actuators in electrical line protection devices face issues with premature tripping due to electromagnetic compatibility tests, particularly from 8/20µs current waves and 1.2/50µs voltage waves, leading to dielectric breakdowns and component deterioration, which current solutions address with additional varistors but at increased cost and reduced compactness.
Innovation Solution
Incorporating a third short-circuited coil interleaved with the differential and magnetic coils to oppose the magnetic field induced by the 8/20µs current wave, reducing the voltage on the differential coil and eliminating the need for additional varistors, thus maintaining compactness and reducing component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional varistor is placed across the terminals of the differential coil to prevent breakdowns from 8/20µs current waves, then the reliability against electromagnetic shocks is improved, but the voltage across the control element increases significantly during 1.2/50µs voltage waves, requiring more expensive components
Solution Approach 1:
A third coil is introduced as an intermediary element between the magnetic coil and differential coil. This intermediate coil, when short-circuited, generates a counteracting magnetic field that mediates the electromagnetic coupling, reducing the induced voltage on the differential coil without requiring additional varistors or resistors
Solution Approach 2:
The invention converts the harmful electromagnetic coupling effect into a beneficial one by utilizing the same coupling mechanism to generate a counteracting magnetic field. The short-circuited third coil transforms the potentially destructive induced voltage into a protective counter-field that reduces the voltage stress on the differential coil and control element
2Reliability
If a resistor is added upstream of the differential coil to limit current through varistors, then the stress on components is reduced, but the compactness of the actuator is compromised
Solution Approach 1:
The third protective coil is merged with the existing magnetic and differential coils within the same spatial envelope. All three coils share the same cylindrical space and are wound on the same core, combining multiple functions (differential protection, magnetic protection, and shock immunity) without increasing the overall actuator volume
3Reliability
If additional varistors are used to protect against 8/20µs current waves, then the immunity to electromagnetic shocks is improved, but the overall device cost increases due to requiring higher voltage rated control elements
Solution Approach 1:
The invention converts the harmful electromagnetic coupling effect into a beneficial one by utilizing the same coupling mechanism to generate a counteracting magnetic field. The short-circuited third coil transforms the potentially destructive induced voltage into a protective counter-field that reduces the voltage stress on the differential coil and control element
Solution Approach 2:
A third coil is introduced as an intermediary element between the magnetic coil and differential coil. This intermediate coil, when short-circuited, generates a counteracting magnetic field that mediates the electromagnetic coupling, reducing the induced voltage on the differential coil without requiring additional varistors or resistors
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents breakdowns from 8/20µs current waves without affecting the actuator's operation during 1.2/50µs voltage waves, allowing for the use of less expensive components and maintaining the actuator's compact design.
Implementation Method 1
by electromagnetic coupling, a high induced voltage appears across the terminals of the first differential coil
Implementation Method 2
a third coil wound in short circuit and interleaved with said differential and magnetic coils, generating a magnetic field opposite to the magnetic field created by the magnetic coil
Data Source
Figure 1~2
AI summary
A line protection electromagnetic actuator, comprising several windings surrounding a movable magnetic core capable of moving from a rest position to an actuating position under the effect of the magnetic field created by the windings, and comprising: - a differential winding (2) generating a magnetic field in response to a differential fault on the current line to be protected; - a magnetic winding (1), engaged with the differential winding (2), and generating a magnetic field in response to a short-circuit fault on the current line to be protected. This electromagnetic actuator is characterised in that it also comprises a third winding (3) wound in a short circuit and engaged with said differential winding (2) and magnetic winding (1), generating a magnetic field opposed to the magnetic field created by the magnetic winding (1).