PCB Motor Controller Using Point-On-Wave Relay Switching
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Solution Overview
Problem
Conventional motor controllers for industrial applications are costly and complex, with recent 'hybrid' devices using solid-state switches that are expensive and offer limited advancements in cost or packaging efficiency.
Innovation Solution
A motor controller system utilizing a printed circuit board with three-phase conductors, a power supply, and control circuitry, along with single-pole relays that employ point-on-wave switching to manage three-phase AC power, allowing for precise control and efficient switching without the need for expensive solid-state switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional motor controllers are used, then motor control functionality is provided, but cost and complexity increase
Solution Approach 1:
The patent employs standard electromechanical relays instead of expensive solid-state switches, accepting that relays have limited life but providing cost-effective motor control. The relays are replaced when worn, rather than using costly solid-state components that would provide longer life but higher initial cost.
Solution Approach 2:
The patent implements point-on-wave switching control that precisely timing the closing of relay contacts to occur at specific points in the AC waveform cycle. This timing parameter optimization reduces transient currents and torque stress, enabling the use of simpler electromechanical relays to achieve performance previously requiring complex solid-state controllers.
2Volume of moving object
If solid-state switches are used in hybrid devices, then packaging size is reduced, but cost increases and further advancement is limited
Solution Approach 1:
The patent uses standard electromechanical relays that can handle multiple functions (switching, protection, control) in a single component, rather than requiring separate solid-state switches, snubbers, and protection circuits. This universal approach simplifies the overall design while maintaining compact packaging.
Solution Approach 2:
The patent accepts the limited life of electromechanical relays in exchange for significant cost reduction and simplified design. The relays are standard off-the-shelf components that can be easily replaced, providing a practical solution that avoids the high cost and complexity of solid-state alternatives.
3Ease of operation
If relays switch at arbitrary times, then control is simple, but transient currents and torque stress increase
Solution Approach 1:
The patent implements point-on-wave switching control that precisely timing the closing of relay contacts to occur at specific points in the AC waveform cycle. This timing parameter optimization reduces transient currents and torque stress, enabling the use of simpler electromechanical relays to achieve performance previously requiring complex solid-state controllers.
Solution Approach 2:
The control circuitry monitors the AC waveform and uses this feedback to determine the optimal moment to close the relay contacts. By detecting waveform characteristics and timing the switching action accordingly, the system minimizes harmful transients while maintaining simple electromechanical relay operation.
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 system reduces transient currents and torque stress during motor starting, extends relay life, and minimizes arcing, achieving reliable and cost-effective motor control with compact, lightweight designs suitable for various industrial applications.
Implementation Method 1
The relays each have a direct current operator that receives control signals from the control circuitry to switch in accordance with a point-on-wave switching scheme to close at desired times of an AC waveform
Implementation Method 2
complete current carrying paths from the source through the power conductors to the motor
Data Source
Figure 1~2A
Figure 2B~3
Figure 4A~5
AI summary
A PCB motor controller comprises relays mounted on a PCB and interconnected to power traces in or on the PCB to receive incoming three-phase power and to output three-phase power to a motor. Control power traces in or on the PCB connect the relays to control circuitry, also mounted on the PCB. A power supply is mounted on the PCB and connected to the control circuitry to provide power for its operation and for switching of the relays. The relays are switched in accordance with a point-on-wave (POW) switching scheme, allowing for the use or relays and the PCB, which may not otherwise be suitable for motor control applications.