Electric Pump Motor Control for High Viscosity Startup
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Solution Overview
Problem
Electric pumps experience excessive load and current when starting up with high viscosity fluids, leading to potential overload beyond rated output, particularly during cold starts.
Innovation Solution
An electric pump device employing open loop control to restrict current supply to the motor during startup, gradually increasing rotational speed stepwise, and transitioning to feedback control once the target speed is approached, with open loop control duration adjusted based on fluid temperature to manage viscosity resistance effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is used at startup of the electric pump, then the motor can be controlled to rotate steadily, but excessive current occurs in the motor beyond rated output due to high viscosity resistance of cold fluid
Solution Approach 1:
The control unit performs open-loop control at startup to preliminarily rotate the motor without feedback, preventing excessive current before feedback control is engaged. This preliminary action allows the motor to overcome the high viscosity resistance of cold fluid without drawing excessive current that would occur if feedback control were immediately applied.
Solution Approach 2:
The control unit dynamically switches from open-loop control to feedback control based on motor rotation speed. Initially, open-loop control is used to start the motor, and when the rotation speed reaches a predetermined value, the control unit transitions to feedback control. This dynamic adjustment resolves the contradiction by adapting the control method to the operational stage.
2Power
If open loop control is used at startup to restrict current, then motor overload is prevented, but the motor takes longer to reach target rotational speed compared to feedback control
Solution Approach 1:
Open-loop control is used preliminarily at startup to restrict current and prevent overload, then feedback control is engaged to accelerate speed acquisition. This two-stage approach balances current restriction with efficient speed attainment.
Solution Approach 2:
The control unit dynamically transitions from open-loop to feedback control based on rotation speed thresholds. This dynamic switching optimizes both current management and speed acquisition time by using the appropriate control method at each operational stage.
3Productivity
If the motor is started with high viscosity fluid, then the pump can operate, but the load on the motor increases excessively due to viscosity resistance
Solution Approach 1:
The control unit performs preliminary open-loop control to gradually rotate the motor before engaging feedback control. This preliminary action reduces the initial load caused by high viscosity fluid by avoiding sudden current surges that would occur with immediate feedback control.
Solution Approach 2:
The control unit changes the control parameter from feedback-based to open-loop-based at startup, and subsequently switches back to feedback control when rotation speed reaches a predetermined value. This parameter change adapts the control strategy to the operational conditions, managing motor load effectively.
Data Source
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AI summary
An electric pump device (1) according to the present invention comprises an oil pump (10) that discharges oil; a motor (20) that drives the oil pump (10); and a control unit (30) that controls the value of current supplied to the motor (20) to control rotation of the motor (20), thereby controlling the flow rate of fluid discharged from the oil pump (10). The device is configured such that at startup of the motor (20), until the rotational speed of the motor (20) comes near to a target rotational speed set beforehand, the motor (20) is driven by open loop control that restricts the value of current supplied to the motor (20) to lower than a predetermined upper limit, and that when the rotational speed of the motor (20) has come near to the target rotational speed, the motor (20) is driven by feedback control that keeps the rotational speed at a steady rotational speed.