Motor Control Device Power Hold Time During AC Failure

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Solution Overview

Problem

Conventional motor control devices face challenges in securing sufficient power to retract driven objects and stop motors without interference when power fails, especially when using smoothing capacitors, as they cannot guarantee the necessary power for both operations simultaneously, leading to limitations in output hold time.

Innovation Solution

A motor control device that includes a current value sampling unit, PWM signal generation unit, and power supply stop unit, which dynamically adjust sampling periods and carrier frequencies based on stored power in the DC link to prioritize power distribution to critical components, ensuring operations like retracting driven objects and stopping motors can be performed during power failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If power is supplied to both the motor control device and peripheral devices during power failure, then the peripheral devices can continue to operate, but the output hold time of the control power source becomes insufficient to complete critical safety operations

Engineering Contradiction:

Improveoutput hold time of control power sourceVSAvoidperipheral device operation during power failure

Core Design Contradiction:

Duration of action of stationary objectVSEase of operation

Solution Approach 1:

The system dynamically adjusts power distribution based on real-time conditions. The determination unit evaluates the state of the DC link capacitor and selectively controls power supply to peripheral devices versus the motor control device, creating a dynamic power management strategy that optimizes output hold time while maintaining essential operations.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes operational parameters by adjusting power supply levels to different components. By modifying the power supply state from the control power source to either the motor control device or peripheral devices based on detected conditions, the system extends output hold time while ensuring critical safety functions can complete.

Inventive Principle:

Principle #35Parameter changes

2Duration of action of stationary object

If the capacitance of the smoothing capacitor is increased to extend output hold time, then sufficient power can be secured for safety operations, but the device complexity and cost increase

Engineering Contradiction:

Improveoutput hold time of control power sourceVSAvoidcapacitance of smoothing capacitor

Core Design Contradiction:

Duration of action of stationary objectVSDevice complexity

Solution Approach 1:

Rather than using a fixed large-capacitance smoothing capacitor, the system employs dynamic power management control. The determination unit and control unit work together to adjust power distribution in real-time, achieving extended output hold time through intelligent control rather than through increased hardware capacitance.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the operational parameters of power distribution rather than changing the physical parameters of the capacitor. By adjusting power supply states and timing, the system achieves the functional equivalent of a larger capacitor without the associated complexity and cost.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If power is prioritized to the motor control device during power failure, then critical safety operations can be completed, but peripheral devices cannot continue to operate

Engineering Contradiction:

Improvesafety operation completionVSAvoidperipheral device operation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system extracts and prioritizes power supply to the essential motor control device during power failure conditions. The determination unit identifies when power failure occurs and the control unit selectively disconnects power to peripheral devices while maintaining power to the motor control device, ensuring safety operations can complete.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system applies different power supply qualities to different components based on their criticality. The motor control device receives prioritized power supply to ensure safety operations, while peripheral devices receive reduced or no power, creating a localized quality differentiation in power distribution.

Inventive Principle:

Principle #3Local quality

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

This approach effectively lengthens the output hold time of the control power source, enabling the motor control device to perform necessary operations even during power failures without increasing the capacitance of the smoothing capacitor, thus ensuring safe and efficient motor control.

Implementation Method 1

power stored in a DC link part connected to an alternating-current power source via a converter

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS8878388B2Motor control device that decreases power consumed by control power source when power fails

Publication Date: 2014.11.04 FANUC LTD

AI summary

A motor control device has a current value sampling unit configured to sample a current value of a motor, a PWM signal generation unit configured to generate a PWM signal to drive the motor, based on the sampled current value of the motor, and a power supply stop unit configured to stop supply of power from a control power supply to a peripheral depending on power stored in a DC link part and power to which the control power source can supply when an alternating-current power source fails.