Contactor Coil Control via PWM Switching
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Solution Overview
Problem
Classic DC drives with electronic coil control suffer from continuous current flow through resistors, leading to heating and unnecessary power loss due to constant energization, which is inefficient and wasteful.
Innovation Solution
A contactor with an energy-efficient coil drive control using a comparator to generate a variable switch-on pulse, controlling field effect transistors to manage the coil's power, allowing for adjustable switching frequency and current flow duration, reducing retaining power without additional loss, and eliminating the need for a controller or firmware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DC drives continuously power the coil, then the contactor operates reliably without error messages, but unnecessary power is consumed and heating occurs
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation (PWM) to energize the coil in periodic pulses rather than continuous DC power. The electronic coil drive controls the duration and frequency of current pulses through the coil, allowing the contactor to maintain operation with intermittent power supply. This reduces average power consumption while ensuring the coil reaches sufficient magnetic field strength during each pulse to actuate the contactor reliably.
2Reliability
If a resistor is connected in parallel to the contactor to solve electronic coil control issues, then the control problem is addressed, but current constantly flows through the resistor causing heating and power loss
Solution Approach 1:
The patent extracts and eliminates the problematic parallel resistor configuration from the circuit. Instead of using a resistor to address coil control issues, the invention employs an electronic coil drive with PWM control that directly manages coil energization. This removes the source of continuous power loss through the resistor while maintaining reliable electronic coil control through the semiconductor-based switching circuitry.
3Adaptability or versatility
If electronic coil drives with high short-term pull-in power are used, then the contactor can be controlled by low-current PLC outputs, but the holding power remains constant and energy-consuming
Solution Approach 1:
The patent applies dynamics by making the holding power adjustable rather than fixed. The electronic coil drive incorporates control circuitry that can vary the PWM duty cycle and frequency to optimize holding power based on actual operational needs. This allows the system to reduce holding power consumption while maintaining sufficient magnetic field strength to keep the contactor actuated, adapting the power level dynamically rather than maintaining constant high power.
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 solution reduces retaining power to freely selectable values, is cost-effective, and can be integrated into existing DC contactors, minimizing space and energy consumption while avoiding unnecessary heating and power loss.
Implementation Method 1
A current in the excitation coil generates a magnetic flux through a ferromagnetic core and a movable ferromagnetic armature. A force is exerted on the armature across an air gap
Data Source
Figure 1
AI summary
The invention relates to a contactor with an energy-efficient coil control, wherein the coil control has connections A1/A2 (1, 2) which, after application of a control voltage, control a coil (3) by means of a switch-on pulse (4) which is formed by a comparator 1 (5), and wherein a comparator 2 (6) is designed as a multivibrator and wherein the comparators 1 and 2 (5, 6) alternately control field-effect transistors FET1 and FET2 (7, 8) on the output side.