Motor Control Apparatus Relay Switching Noise Reduction
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Solution Overview
Problem
Existing motor control apparatuses face challenges in smoothly controlling the rotational driving frequency of high-capacity motors or multiple motors, often resulting in noise and overshoot due to the use of expensive large-capacity PWM control circuits and the lack of soft start or soft stop control, which can lead to fluctuations in motor rotation and increased manufacturing costs.
Innovation Solution
A motor control apparatus that utilizes a control module with relay units and a relay changeover portion to manage control currents between pairs of brushes, implementing soft start or soft stop control functions, and generating waveforms with the same cycle to synchronize motor rotations, thereby reducing noise and allowing for variable control of motor speed without increasing the number of parts or manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large-capacity PWM control circuit is used to control high-capacity motors or multiple motors, then the motor control capability is improved, but the manufacturing cost increases
Solution Approach 1:
The motor control apparatus divides the control function into two independent relay units: a first relay unit for lower speed rotation control and a second relay unit for higher speed rotation control. Each relay unit handles a specific speed range, allowing the use of smaller, less expensive relay units instead of requiring a single large-capacity PWM control circuit to handle the entire power range.
Solution Approach 2:
The control module is designed to perform multiple functions by controlling different relay units for different operating conditions. The same control module can switch between controlling the first relay unit for lower speeds and the second relay unit for higher speeds, making the control system versatile without requiring separate control circuits for each speed range.
2Adaptability or versatility
If relay units are switched between ON and OFF states to control motor speed ranges, then the control flexibility is improved, but noise and overshoot occur
Solution Approach 1:
The control module suspends control current output from the first relay unit before switching to the second relay unit. This preliminary suspension action prevents overlapping current transitions that would cause noise and overshoot, ensuring a smooth transition between speed ranges without harmful electrical transients.
Solution Approach 2:
The control module acts as an intermediary between the relay units and the motor, managing the transition smoothly. By coordinating the suspension of the first relay unit and the activation of the second relay unit, the control module mediates the switching process to eliminate noise and overshoot that would otherwise occur during direct relay switching.
3Stability of the object's composition
If soft start or soft stop control is implemented to reduce motor rotation fluctuations, then the motor operation smoothness is improved, but noise is emphasized when relay units are switched
Solution Approach 1:
The control module suspends the control current from the first relay unit before switching to the second relay unit, even during soft start or soft stop operations. This preliminary suspension prevents the interaction between soft start/stop current changes and relay switching currents, eliminating the noise emphasis that would otherwise occur while maintaining the smooth motor operation benefits.
Data Source
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AI summary
A problem is to provide a motor control apparatus which can smoothly control rotations inexpensively and with a large capacity without increasing the number of parts even if the work to be driven and controlled increases. In a control portion 28, a brush pair (8P and 8N or 9P and 9N) for generating a rotationally driving force in each first, second motor 11, 12 is selected by a relay changeover portion 19b of an engine control system 19, and a relay unit 17, 27 is changed over. Here, a control current from the relay unit 17 is temporarily suspended, and the other relay unit 27 is changed over to a current-conductive state. The control portion 28 is also connected to a first drive portion 31 and a second driver portion 32 to supply first and second control signals b1 and b2 thereto respectively. The first and second control signals b1 and b2 serves as synchronization signals from a PWM carrier generating portion 40 to contribute to PWM driving control of the first and second motors 11 and 12 together with rectangular waves k having the same cycle and the same wavelength.