PWM Start-Up Switching for Lower DC Motor Inrush Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushed DC motors experience high peak start-up currents, leading to increased costs due to the need for high-quality electronic components and a risk of component burning during long-term use, necessitating a reduction in start-up current.
Innovation Solution
A start-up device for DC motors that includes a switching element connected in series with the motor and power supply, controlled by a unit to periodically switch between ON and OFF states using pulse width modulation, with a predetermined time interval to reduce peak start-up currents and maintain the ON state after the interval ends, optionally including overcurrent protection and electromagnetic pulse absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-quality electronic components are used to handle high start-up current, then the motor can start reliably, but product cost increases
Solution Approach 1:
The patent applies periodic switching action through PWM control during motor start-up. The switching element periodically switches between ON and OFF states in a predetermined time interval, creating a controlled start-up current profile that limits peak current while maintaining reliable motor starting. This periodic action eliminates the need for expensive high-current components.
2Reliability
If high-quality electronic components are used to handle high start-up current, then the motor can start reliably, but component burning risk during long-term use increases
Solution Approach 1:
The periodic switching during start-up reduces peak current stress on components. By controlling the switching element to operate in PWM mode during the predetermined time interval, the patent limits the peak start-up current to a safe level, preventing component overheating and burning during long-term use while still achieving reliable motor starting.
Solution Approach 2:
The switching element acts as an intermediary between the power supply and motor during start-up. It mediates the current flow by periodically switching, thereby protecting downstream components from excessive current stress and potential burning while still enabling the motor to start reliably.
3Object-generated harmful factors
If switching element periodically switches during start-up, then peak start-up current is reduced, but control complexity increases
Solution Approach 1:
The control unit automatically generates the PWM control signals and manages the switching element operation without requiring external complex control circuits. The predetermined time interval and switching frequency are internally managed, making the system self-sufficient and reducing overall control complexity despite the periodic switching requirement.
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
The solution effectively reduces peak start-up currents, lowering component stress and costs by controlling the switching element's state transitions and frequency, thereby enhancing the reliability and efficiency of DC motor start-up.
Implementation Method 1
a control unit configured to cause the switching element to periodically switch between an ON state and an OFF state in a predetermined time interval to reduce a peak value of a start-up current flowing through the DC motor
Implementation Method 2
a capacitor connected between positive and negative terminals of the DC motor to absorb electromagnetic pulse components generated by the DC motor
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present application relates to a motor control technology, and in particular to a start-up device (10) for a DC motor (12). The start-up device (10) includes: a switching element (110) connected in series within a circuit comprising the DC motor (12) and a DC power supply (11); and a control unit (120) configured to cause the switching element (110) to periodically switch between an ON state and an OFF state in a predetermined time interval (Ts) to reduce the peak value of a start-up current (Ip) flowing through the DC motor (12), and to cause the switching element (110) to maintain the ON state after the predetermined time interval (Ts) ends.