Motor Drive Reactive Current Control for Voltage Suppression

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Solution Overview

Problem

Existing motor driving devices face challenges in suppressing abnormal excessive voltage, leading to potential damage and increased cost due to the need for large-capacity regeneration resistors or regenerative circuits, which also occupy more space.

Innovation Solution

A motor driving device with a converter, inverter, voltage detecting unit, and numerical control unit that outputs a reactive current when the detected voltage exceeds a threshold, increasing power consumption in the motor to suppress excessive voltage without additional hardware.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large-capacity regeneration resistor or regenerative circuit is provided to suppress abnormal excessive voltage, then the converter is protected from damage, but the device complexity and cost increase

Engineering Contradiction:

Improveconverter protectionVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the voltage suppression function from dedicated hardware components (regeneration resistors and regenerative circuits) and relocates it to the control unit through software-based reactive current instruction generation. This removes the need for additional protective hardware while maintaining converter protection functionality.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The control unit is given multiple functions: it not only controls the inverter for normal motor operation but also generates reactive current instructions to suppress excessive voltage during regeneration. This multi-functionality eliminates the need for separate protection circuits, reducing device complexity while maintaining reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a large-capacity regeneration resistor or regenerative circuit is provided to suppress abnormal excessive voltage, then the converter is protected from damage, but the occupied space increases

Engineering Contradiction:

Improveconverter protectionVSAvoidoccupied space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent removes the physical regeneration resistor and regenerative circuit components from the system by implementing voltage suppression functionality in the control unit's software. This extraction eliminates the occupied space that would be required for these additional hardware components.

Inventive Principle:

Principle #2Taking out (Extraction)

3Speed

If the motor regenerates excessive electric power during deceleration, then the motor speed is reduced, but abnormal excessive voltage is generated on the direct current output side

Engineering Contradiction:

Improvemotor speedVSAvoidexcessive voltage

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The control unit continuously monitors the direct current output voltage from the converter and uses this feedback to determine when excessive voltage occurs during motor deceleration. Based on this feedback, the control unit dynamically adjusts the reactive current instruction to suppress the excessive voltage while allowing the motor to decelerate normally.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent converts the harmful regenerated electric power that causes excessive voltage into a beneficial effect by using it to generate reactive current in the motor. This reactive current increases power consumption in the motor, which effectively suppresses the excessive voltage on the direct current output side while utilizing the regenerated energy rather than dissipating it as waste heat in a resistor.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Effectively suppresses abnormal excessive voltage without additional hardware, reducing costs and space requirements while allowing flexible handling of operational changes through software adjustments.

Implementation Method 1

a reactive current instruction generating unit configured to generate a reactive current instruction for causing the inverter to output a reactive current in accordance with a voltage detected by the voltage detecting unit when the voltage monitoring unit determines that a voltage detected by the voltage detecting unit exceeds a predetermined threshold

Methodology Applied

Scientific EffectReactive current:

Data Source

PatentUS9048733B2Motor driving device having reactive current instruction generating unit

Publication Date: 2015.06.02 FANUC LTD

AI summary

A motor driving device includes a converter that converts an input alternating current into a direct current, an inverter that inverts the direct current output by the converter into an alternating current for driving a motor, a voltage detecting unit that detects a voltage on a direct current output side of the converter, and a numerical control unit that causes the inverter to output a reactive current to increase electric power consumed in the motor, when the voltage detected by the voltage detecting unit exceeds a predetermined threshold.