Shunt Regulator Overvoltage Protection TRU Output

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Solution Overview

Problem

Overvoltage conditions in electrical generating systems, particularly in aircraft systems, can cause damage to critical loads due to the rapid voltage rise in variable frequency generators, which traditional overvoltage protection circuitry may fail to detect in time, leading to potential catastrophic events.

Innovation Solution

A shunt regulator is connected to the output of a transformer rectifier unit (TRU) to actively limit the output voltage by overloading the TRU when an overvoltage condition is detected, ensuring the voltage on the DC bus does not exceed a reference voltage, thereby providing a protective mechanism until the overvoltage protection modules in the generator control unit can react.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional overvoltage protection modules are used in generator control unit, then the system structure is simple, but the response time is too slow (10-100 ms) to protect critical loads from rapid voltage rise

Engineering Contradiction:

Improveovervoltage protection effectivenessVSAvoidresponse time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The shunt regulator is pre-positioned at the TRU output and immediately activates when overvoltage is detected, performing protective action before the main overvoltage protection modules can respond. This preliminary protective measure clamps the voltage within milliseconds, bridging the critical response time gap until the main protection systems can disconnect the generator.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If variable frequency generator is used to improve system flexibility, then adaptability is improved, but overvoltage protection becomes ineffective due to rapid voltage rise exceeding detection capability

Engineering Contradiction:

Improvesystem flexibilityVSAvoidovervoltage protection reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The shunt regulator acts as an intermediary protective device between the TRU output and the critical DC loads. It provides intermediate voltage clamping protection that operates independently and faster than the main overvoltage protection system, ensuring that even with VF generator flexibility, the loads are protected from rapid voltage transients.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If shunt regulator is activated to overload TRU output for protection, then voltage is limited to safe levels, but energy loss increases during overvoltage condition

Engineering Contradiction:

Improveload protectionVSAvoidenergy dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The shunt regulator applies preliminary protective action by clamping the voltage at safe levels during overvoltage conditions. While this does dissipate some energy, it prevents catastrophic damage to critical loads. The regulator operates only temporarily during overvoltage events until the main protection systems can disconnect the generator, minimizing total energy loss while ensuring load safety.

Inventive Principle:

Principle #9Preliminary anti-action

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 a fast and effective response to overvoltage conditions, protecting critical loads by maintaining the voltage within safe limits until the overvoltage protection modules can disconnect the generator, thus preventing damage to flight-critical equipment.

Implementation Method 1

an operational amplifier, the operational amplifier configured to receive a reference voltage and an output voltage of the TRU as inputs

Methodology Applied

Scientific EffectOperational amplifier voltage amplification:

Implementation Method 2

a transistor, the transistor configured to receive an output of the operational amplifier as a gate voltage, the output voltage of the TRU as a source voltage, and wherein a drain of the transistor is connected to ground

Methodology Applied

Scientific EffectField effect transistor conductivity control:

Implementation Method 3

the shunt regulator configured to overload the output of the TRU in the event of an overvoltage condition at the output of the TRU

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS8699188B2Shunt regulator for overvoltage protection at transformer rectifier unit of electrical generating system

Publication Date: 2014.04.15 HAMILTON SUNDSTRAND CORP

AI summary

An electrical system includes an alternating current (AC) source; a transformer rectifier unit (TRU) connected to the AC source, the TRU configured to receive AC power from the AC source, convert the AC power to direct current (DC) power, and output DC power; a DC bus configured to receive the DC power output by the TRU; at least one DC load powered by the DC bus; and a shunt regulator connected to the output of the TRU, the shunt regulator configured to overload the output of the TRU in the event of an overvoltage condition at the output of the TRU, such that a voltage available to the DC bus during the overvoltage condition does not exceed a reference voltage.