Interposition Inductor for Parallel Drive Current Balancing

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Solution Overview

Problem

When multiple drives are placed in parallel, circulating currents can reduce efficiency and lead to unequal current sharing, and may result in reduced voltage, limiting the operable range of load devices, such as elevator motors.

Innovation Solution

The use of interposition inductors with conductors wound around magnetic cores, where the number of turns is calculated to balance currents and voltages across phases, actively controlling current to limit circulating currents and ensure equal current sharing between drives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If two or more drives are placed in parallel to support heavy duty applications, then the power and current capacity is increased, but circulating currents occur that reduce efficiency and cause unequal current sharing

Engineering Contradiction:

Improvepower capacityVSAvoidcirculating currents

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

An interposition inductor is introduced as an intermediary component between parallel drives. The inductor has a first winding connected to a first drive and a second winding connected to a second drive, with the windings wound in opposite directions around the same magnetic core. This configuration causes magnetic fluxes generated by the two drives to oppose each other, thereby limiting circulating currents between the drives while maintaining equal current sharing.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If two or more drives are placed in parallel to increase power capacity, then more drives are added, but voltage is reduced thereby limiting the operable range of load devices

Engineering Contradiction:

Improvepower capacityVSAvoidvoltage stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The interposition inductor acts as a mediator that prevents voltage reduction when drives are operated in parallel. By limiting circulating currents through opposing magnetic fluxes, the inductor maintains stable voltage levels at the system output, ensuring that load devices operate within their required voltage ranges and expanding the operable speed range of motors.

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 effectively limits circulating currents and ensures equal current sharing between drives, maintaining system voltage and expanding the operable speed range of load devices.

Implementation Method 1

at least one inductor (100) including at least one conductor wound around at least one magnetic core

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

at least one conductor wound around at least one magnetic core formed from a magnetic material

Methodology Applied

Scientific EffectMagnetic flux: Magnetic Field

Data Source

PatentEP3262750B1Interposition inductor arrangement for multiple drives in parallel

Publication Date: 2020.01.29 OTIS ELEVATOR CO

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AI summary

A power system including a first drive including a first drive output, a second drive including a second drive output, wherein the first drive output is larger than the first drive output, at least one inductor operably coupled to the first drive and the second drive, and a load operably coupled to the system output.