Motor Control Torque Command Limit Unit for Power Outage
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Solution Overview
Problem
Existing motor control devices face challenges in stopping motors quickly during power failures without generating a low voltage alarm, as excessive deceleration torque can lead to electric power consumption rather than regeneration, causing the DC link voltage to decrease and triggering a low voltage alarm, which prolongs the stopping distance.
Innovation Solution
A motor control device with a power failure detection unit, DC link voltage detection, comparison unit, torque command generation, torque limit value setting, and torque command limiting units, which adjust the torque command based on DC link voltage thresholds to limit the deceleration torque, ensuring regeneration rather than consumption and preventing low voltage alarms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If deceleration torque is increased to shorten stopping distance, then stopping distance is reduced, but electric power is consumed instead of regenerated causing DC link voltage to decrease and triggering low voltage alarm
Solution Approach 1:
The patent applies dynamics by making the torque command adaptive rather than fixed. The torque command is dynamically adjusted based on real-time DC link voltage levels, allowing the system to optimize deceleration performance while preventing harmful effects. When DC link voltage is high, larger deceleration torque is applied to shorten stopping distance; when DC link voltage drops below threshold, torque is reduced to prevent power consumption and low voltage alarm
Solution Approach 2:
The patent changes the parameter of torque command based on DC link voltage conditions. By monitoring DC link voltage and adjusting the torque command accordingly (increasing when voltage is high, decreasing when voltage is low), the system resolves the contradiction between achieving short stopping distance and avoiding power consumption that triggers low voltage alarm
2Duration of action of moving object
If deceleration torque is increased to secure long deceleration time, then deceleration time is extended, but electric power consumption increases reducing available electric power in DC link
Solution Approach 1:
The patent changes the torque parameter dynamically based on DC link voltage to optimize energy utilization. When DC link voltage is high, the system allows larger torque for faster deceleration; when voltage drops, torque is reduced to prevent power consumption. This parameter adaptation resolves the contradiction between extending deceleration time and minimizing power consumption
3Loss of energy
If torque command is limited to prevent power consumption, then power consumption is reduced enabling regeneration, but stopping distance increases
Solution Approach 1:
The patent applies dynamics by making torque command adaptive rather than statically limited. Instead of continuously limiting torque to prevent power consumption, the system dynamically adjusts torque based on DC link voltage: allowing high torque when voltage is high (enabling fast stopping) and reducing torque only when voltage drops (preventing power consumption). This dynamic approach resolves the contradiction between minimizing power loss and achieving short stopping distance
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 device effectively shortens the stopping distance of the motor while avoiding low voltage alarms by dynamically adjusting the torque limit value based on DC link voltage, ensuring efficient energy use and reliable operation during power failures.
Implementation Method 1
a method of generating a deceleration torque in the motor (hereinafter referred to as deceleration by control), and a method of applying a dynamic brake by connecting a resistance to the motor and allowing a current to flow therethrough, thereby allowing energy to be consumed (hereinafter referred to as deceleration by hardware)
Data Source
AI summary
A motor control device which controls a motor in a machine tool or an industrial machine includes: a power outage detection unit that detects a power outage of a power source which supplies electric power for driving the motor; a DC link voltage detection unit that detects a value of a DC link voltage applied to an amplifier which drives the motor; a comparison unit which compares the value of the DC link voltage with a predetermined threshold value; a torque command generation unit which generates a torque command for driving the motor; a torque limit value setting unit which sets a torque limit value in accordance with a result of a comparison by the comparison unit; and a torque command limit unit which limits the torque command to the torque limit value when a power outage is detected by the power outage detection unit.