Power Converter Cooling System Pump Control

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Solution Overview

Problem

The existing cooling systems for power converters in on-vehicle rotary electric machines face challenges in controlling the coolant flow rate effectively, particularly with regards to the concentration of antifreeze solution, which affects the heat transfer rate and energy consumption.

Innovation Solution

A cooling system that includes a heat quantity calculation unit, temperature acquisition units, a heat transfer rate calculation unit, and a pump control unit to adjust the coolant flow rate based on the calculated heat transfer rate and temperature differences, as well as a concentration calculation unit to monitor antifreeze solution concentration and issue alarms for freezing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the flow rate of coolant is increased to improve heat transfer, then cooling performance is improved, but energy consumption of the pump increases

Engineering Contradiction:

Improvecooling performanceVSAvoidenergy consumption

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The pump operates in multiple discrete flow rate modes (first through fourth flow rates) rather than a single fixed rate, allowing the system to dynamically adjust coolant flow based on actual heat transfer requirements and ambient conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes operational parameters by selecting different pump flow rates based on calculated heat transfer rates and ambient temperature, optimizing the balance between cooling performance and energy consumption

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the concentration of antifreeze solution is increased to prevent freezing, then freezing protection is improved, but heat transfer rate decreases

Engineering Contradiction:

Improvefreezing protectionVSAvoidheat transfer rate

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The system calculates the heat transfer rate based on measured temperatures and heat generation, then uses this feedback to determine appropriate pump flow rate adjustments that compensate for reduced heat transfer efficiency caused by antifreeze concentration

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Instead of mechanically adjusting antifreeze concentration, the system substitutes by dynamically adjusting pump flow rate to compensate for the thermal effects of antifreeze presence

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If the pump operates at high flow rate continuously, then cooling reliability is improved, but energy consumption increases

Engineering Contradiction:

Improvecooling reliabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system uses a higher flow rate than strictly necessary for basic cooling, then reduces to lower flow rates when sufficient cooling is achieved, preventing both under-cooling and excessive energy consumption

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The pump flow rate is adjusted periodically based on changing operating conditions, alternating between different flow rate levels to match actual cooling demands

Inventive Principle:

Principle #19Periodic 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 reduces energy consumption by optimizing coolant flow and air flow, ensuring efficient heat transfer and preventing coolant freezing, thereby enhancing the reliability and efficiency of the cooling system.

Implementation Method 1

a cooling circuit which has a circulation pump (6) to circulate a coolant

Methodology Applied

Scientific EffectForced Convection: Forced Convection

Implementation Method 2

cools down, by using the coolant, a power element mounted in a power converter

Methodology Applied

Scientific EffectHeat Transfer: Conduction (thermal)

Implementation Method 3

a heat exchanger (5) which is provided in the cooling circuit to exchange heat between outside air and the coolant

Methodology Applied

Scientific EffectHeat Exchange: Heat Exchanger

Implementation Method 4

a blower (8) which blows outside air to the heat exchanger (5)

Methodology Applied

Scientific EffectForced Convection: Forced Convection

Data Source

PatentUS9768668B2Cooling system of power converter for on-vehicle rotary electric machine

Publication Date: 2017.09.19 ASTEMO LTD

AI summary

A cooling system includes a cooling circuit that has a circulation pump circulating a coolant containing antifreeze solution and cools down, by means of the coolant, a power element mounted in a power converter for an on-vehicle rotary electric machine; a control signal calculation unit that calculates heat quantity generated by the power element; a power element temperature sensor that detects the temperature of the power element; and a coolant temperature sensor that detects the temperature of the coolant. The control signal calculation unit calculates, on the basis of the heat quantity, the temperature of the power element, and the coolant temperature, power element cooling performance that is the amount of heat transferred from the power element to the coolant per unit temperature difference, and lowers the driving power of the circulation pump when the calculated power element cooling performance is greater than a predetermined criterion.