Motor Drive Voltage Drop Correction for Hoist Continuity
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Solution Overview
Problem
Conventional motor drive apparatuses for hoisting and crane operations become uncontrollable and inefficient when AC power voltage drops, leading to potential motor shutdowns and DC overvoltage issues during regenerative braking.
Innovation Solution
A motor drive apparatus with a voltage drop detector, converter control unit, and inverter control unit that corrects the motor speed command based on detected voltage drops, preventing shutdowns and maintaining operation within safe parameters by adjusting the speed reference and output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor drive apparatus stops when voltage drop is detected, then the motor is protected from damage, but the work efficiency deteriorates and operation continuity is lost
Solution Approach 1:
The invention changes the control parameters of the motor drive apparatus during voltage drop conditions. Specifically, it adjusts the speed command value and output current limits dynamically based on the detected voltage level, allowing the motor to continue operating within safe parameter ranges rather than shutting down completely.
Solution Approach 2:
The system transitions from a static stop/go control approach to a dynamic continuous operation mode. The control unit continuously monitors voltage levels and adjusts operating parameters in real-time, enabling the motor to adapt its performance dynamically during voltage fluctuations while maintaining operation.
2Reliability
If regenerative braking is forcibly started during acceleration control, then the motor can be controlled during power failure, but DC voltage fluctuates greatly and DC overvoltage may occur
Solution Approach 1:
The invention implements feedback control by continuously monitoring DC voltage levels and using this information to adjust the speed command and output current limits. The control unit modifies operating parameters based on real-time DC voltage feedback, preventing overvoltage conditions while maintaining motor control during power fluctuations.
Solution Approach 2:
The system takes preliminary protective action by detecting voltage drops before they cause damage and preemptively adjusting control parameters. The control unit anticipates potential DC overvoltage issues by limiting output current and adjusting speed commands in advance, preventing harmful voltage fluctuations before they occur.
3Productivity
If the inverter continues operation during voltage drop, then productivity is maintained, but the apparatus must operate within limited voltage range requiring precise control
Solution Approach 1:
The control unit performs self-adjustment by automatically modifying speed commands and current limits based on detected voltage conditions. The system serves itself by using its own voltage detection capability to autonomously regulate its operation, eliminating the need for external intervention or complex external control systems.
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 apparatus continues operation without stopping during voltage drops, maintaining efficiency and preventing DC overvoltage, ensuring reliable hoisting and lowering operations.
Implementation Method 1
a converter that receives an AC power from an AC power supply and supplies it to a DC circuit
Implementation Method 2
an inverter that converts the power from the DC circuit into a variable frequency AC power, and drives an motor
Data Source
AI summary
A motor drive apparatus that can continue operation within the upper limit of system control even if a voltage drop of an AC power source occurs during operation of a motor used for a hoist or a crane is provided. The inverter control unit of the motor drive apparatus includes a speed reference setting means for setting the rotation speed of the motor, means for detecting a speed deviation between the output of the rotation speed detection means for detecting the rotation speed of the motor and the output of the speed reference setting means, means for controlling the output current of the inverter according to the output of the speed deviation. The speed reference setting means includes a correction circuit for correcting an external speed command given from outside. The correction circuit corrects the external speed command according to a deviation between a detection value of a DC voltage and a first reference value when a voltage drop signal is received from the voltage drop detection means, and makes the corrected speed command as the output of the speed reference setting means.