Motor Control Apparatus Counter Electromotive Force Protection Circuit
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Solution Overview
Problem
In motor control apparatuses, large energy generated by counter electromotive force during sudden motor stoppage cannot be effectively regenerated, leading to increased DC link voltage, which can exceed the capacitor's withstanding voltage, potentially causing the DC link capacitor and main power conversion circuit to break, especially when the counter electromotive force protection circuit fails.
Innovation Solution
A motor control apparatus with a counter electromotive force protection circuit that includes a rectifier unit, a short-circuit unit, and an alarm signal output unit, along with a monitoring and protection operation unit, to manage and consume the energy safely, preventing damage by monitoring for abnormalities and taking protective measures such as gentle acceleration/deceleration or free run stop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor is large or rotates at high speed, then the counter electromotive force energy generated during sudden stoppage becomes extremely large, but the energy cannot be regenerated into the alternating current power supply or regeneration load
Solution Approach 1:
The patent extracts the harmful counter electromotive force energy from the motor during sudden stoppage and directs it through a protection circuit that includes a rectifier unit and short-circuit unit, separating this energy path from the normal regeneration path to the AC power supply or regeneration load
Solution Approach 2:
The patent converts the harmful counter electromotive force energy, which would otherwise cause DC link voltage to exceed capacitor withstanding voltage and damage the main power conversion circuit, into a controlled energy dissipation path through the protection circuit, preventing damage while managing the large energy effectively
2Reliability
If the DC link voltage exceeds the capacitor's withstanding voltage, then the DC link capacitor and main power conversion circuit may break, but providing a counter electromotive force protection circuit may fail to consume the energy when faulty
Solution Approach 1:
The patent implements a monitoring unit that continuously monitors the operation state of the protection circuit in advance, detecting abnormalities before they lead to failure, and enables the control unit to take preliminary protective actions
Solution Approach 2:
The patent prepares a backup protection mechanism where, upon detecting protection circuit abnormalities, the control unit switches to an alternative protection mode that gently accelerates or decelerates the motor to prevent counter electromotive force energy from damaging the DC link capacitor and main power conversion circuit
3Reliability
If the monitoring unit detects abnormality in the alarm signal output unit, then the protection operation unit can perform protection operations, but the device complexity increases
Solution Approach 1:
The patent merges the monitoring function, alarm signal generation, and protection operation control into an integrated control system where the control unit performs multiple functions: monitoring protection circuit operation, generating alarm signals, and executing protection operations, thereby reducing overall system complexity
Solution Approach 2:
The control unit is designed with multi-functionality, serving as both the monitor of protection circuit operation, the alarm signal generator, and the protection operation executor, allowing one component to perform multiple critical functions rather than requiring separate dedicated components for each function
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
Prevents damage to the DC link capacitor and main power conversion circuit by effectively managing energy from counter electromotive force, suppressing voltage increases, and ensuring safe operation even in case of protection circuit failures.
Implementation Method 1
a rectifier unit that rectifies alternating current power based on counter electromotive force of the motor and outputs direct current power
Implementation Method 2
a short-circuit unit that short-circuits terminals on a direct current output side of the rectifier unit
Implementation Method 3
energy on the basis of counter electromotive force is generated in the motor when the motor is urgently stopped
Data Source
AI summary
A motor control apparatus includes: a main power conversion circuit that converts power that is supplied from a power supply into alternating current power for driving a motor, and outputs the alternating current power; a counter electromotive force protection circuit including a rectifier unit that rectifies alternating current power based on counter electromotive force of the motor and outputs direct current power, a short-circuit unit that short-circuits terminals on a direct current output side of the rectifier unit, and an alarm signal output unit that outputs an alarm signal at occurrence of an abnormality; a monitoring unit that monitors whether the alarm signal is output from the alarm signal output unit; and a protection operation unit that performs a protection operation for preventing damage to the main power conversion circuit when the monitoring unit determines that the alarm signal is output from the alarm signal output unit.