Inverter Contactor Drive Circuit for Motor Efficiency

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Solution Overview

Problem

Existing drive circuits for induction motors in applications like fluid pumping and agriculture face inefficiencies at low load conditions and are limited by power factor and electromagnetic interference, as they are typically fixed speed and operate less efficiently when not at line frequency power.

Innovation Solution

A drive circuit comprising an inverter and a contactor that supplies variable frequency current to the motor windings under low load conditions and switches to line frequency current when the inverter is disabled, allowing for efficient operation across varying load conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a fixed speed motor operates at line frequency power, then the motor operates most efficiently at high load conditions, but the motor operates less efficiently at low load conditions

Engineering Contradiction:

Improvemotor efficiencyVSAvoidload condition adaptability

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The system dynamically switches between two operating modes: inverter-driven variable frequency operation for low load conditions and line frequency operation for high load conditions. This dynamic adaptation allows the motor to maintain high efficiency across varying load conditions by selecting the appropriate drive mode based on actual demand.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the electrical parameters supplied to the motor by switching between inverter-generated variable frequency power and utility line frequency power. This parameter change enables the motor to operate efficiently at different load levels by adjusting the frequency and voltage characteristics of the supplied power.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If a variable speed motor controller is used to adapt motor speed to load level, then the motor can operate efficiently at varying loads, but the system is limited by power factor and electromagnetic interference

Engineering Contradiction:

Improvemotor efficiencyVSAvoidelectromagnetic interference

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The system extracts and eliminates the inverter component from the drive circuit, replacing it with a simple contactor that switches between inverter power and line frequency power. By removing the inverter, the system eliminates the source of electromagnetic interference and power factor issues while retaining the ability to operate efficiently at varying loads through dual-mode operation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system replaces the complex, expensive inverter with a simple, inexpensive contactor for the line frequency connection. While the inverter is used for low load operation, the contactor provides a reliable and cost-effective solution for high load operation, reducing overall system complexity and cost.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Use of energy by moving object

If an inverter is used to supply variable frequency current, then the motor can operate efficiently at low load conditions, but the inverter causes electromagnetic interference and power factor limitations

Engineering Contradiction:

Improvemotor efficiencyVSAvoidelectromagnetic interference

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The contactor serves as an intermediary device that switches between inverter output and utility line frequency power. This intermediary allows the system to benefit from inverter-driven efficient operation at low loads while eliminating the harmful electromagnetic interference by disconnecting the inverter and connecting clean line frequency power at high loads.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution enables efficient operation of electric motors at both high and low load conditions, improving power factor, reducing electromagnetic interference, and allowing for variable speed operation, thereby enhancing overall motor efficiency and control.

Implementation Method 1

The inverter is configured to supply variable frequency current to the plurality of windings

Methodology Applied

Scientific EffectElectrical energy conversion:

Implementation Method 2

The contactor is configured to supply the line frequency current to the plurality of windings after the inverter is disabled

Methodology Applied

Scientific EffectElectrical switching:

Data Source

PatentUS10840830B2Drive circuit for electric motors

Publication Date: 2020.11.17 REGAL BELOIT AMERICA INC

AI summary

A drive circuit for an electric pump motor is provided. The drive circuit includes an inverter and a contactor. The inverter is configured to supply variable frequency current to the electric motor. The contactor is configured to supply the line frequency current to the electric motor.