Over-voltage Prevention Device for Wound-Rotor Induction Machines

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional over-voltage prevention systems for wound-rotor induction machines face challenges in quickly recovering from power failures, leading to prolonged downtime and potential damage due to high voltages, as they rely on costly oversized components and mechanical breakers that can cause thermal issues and arcs.

Innovation Solution

A secondary over-voltage prevention device with a current rectifying circuit using a thyristor-based short-circuit device and a controller to manage short-circuiting and restarts, along with a resistor network to minimize current flow and prevent reactivation, allowing for rapid recovery and continuous operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional over-voltage prevention systems use mechanical breakers and oversized components, then reliability is improved, but device complexity and cost increase

Engineering Contradiction:

Improveover-voltage protection reliabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical breakers with a semiconductor-based switching device (IGBT) and electronic control circuitry. The switching device is controlled by a controller that detects over-voltage conditions and activates the switching device to short-circuit the secondary winding, eliminating the need for mechanical breakers and their associated complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operational parameters of the prevention system by using electronic switching instead of mechanical switching. The switching device can rapidly change its resistance state from high to low, enabling fast response to over-voltage conditions without the physical limitations of mechanical components.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If mechanical breakers are used for short-circuiting, then over-voltage protection is achieved, but thermal issues and arcs occur

Engineering Contradiction:

Improveover-voltage protectionVSAvoidthermal issues

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent substitutes mechanical breakers with a semiconductor switching device that can handle high currents without the thermal and arcing problems of mechanical contacts. The IGBT-based switching device dissipates heat more efficiently and eliminates arc formation inherent in mechanical switching.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If the system waits for the induction machine time constant to expire before restarting, then safety is improved, but recovery time increases

Engineering Contradiction:

ImprovesafetyVSAvoidrecovery time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements preliminary monitoring of the secondary winding voltage by the controller. When an over-voltage condition is detected, the controller immediately activates the switching device to short-circuit the winding. After the over-voltage condition resolves, the controller can quickly deactivate the switching device and restart the frequency converter without waiting for the full induction machine time constant to expire, as the controller continuously monitors safety conditions.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If oversized components are used for over-voltage prevention, then protection capability is improved, but cost increases

Engineering Contradiction:

Improveover-voltage protection capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses a dynamically controllable switching device that can rapidly change its state based on operating conditions. The switching device is controlled by a controller that monitors the secondary winding voltage and activates the switching device only when over-voltage conditions are detected, allowing for smaller, more cost-effective components compared to oversized static protection devices.

Inventive Principle:

Principle #15Dynamics

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

Enables rapid recovery from power failures without relying on the time constant of the induction machine, reducing the risk of thermal issues and arcs, and allowing for cost-effective and reliable continuous operation.

Implementation Method 1

a current rectifying circuit comprising a thyristor-based short-circuit device

Methodology Applied

Scientific EffectElectrical short-circuiting: Conduction (electrical)

Implementation Method 2

along with a resistor network to minimize current flow and prevent reactivation

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP2899824B1Over-voltage prevention device and current rectifying circuit

Publication Date: 2021.08.18 KK TOSHIBA

Figure 1
Figure 2
Figure 3

AI summary

According to one embodiment, an over-voltage prevention device includes a first short-circuit device (12) provided between a secondary side of a wound-rotor induction machine (1) and a frequency converter (7) configured to excite the secondary side by a three-phase AC current and having a function of shortcircuiting between phases of the three-phase AC current, resistors (13) each connected between the first short-circuit device (12) and the frequency converter (7) for each phase, and second short-circuit devices (14) connected respectively to the resistors (13) in parallel and having a function of shortcircuiting between the frequency converter (7) and the secondary side of the wound-rotor induction machine (1).