Brushless ISG Winding Layout for Lower Back-EMF and Higher Torque
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Solution Overview
Problem
Conventional Integrated Starter Generator (ISG) systems face challenges such as high back-emf voltage per unit RPM, which limits torque production, increased short-circuit current leading to heat generation, and vulnerability to sensor failures due to high temperatures and vibrations, making them inefficient and prone to mechanical issues.
Innovation Solution
A three-phase brushless DC electric machine with 3n stator teeth and 4n rotor poles, where the back-emf constant is between 25% and 75% of the nominal battery voltage, and stator teeth are wound in a specific directional pattern to reduce back-emf and increase magnetic flux density, allowing for sensor-less operation and improved torque production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If BLDC machines with high back-emf voltage per unit RPM are used, then the machine can generate sufficient voltage for alternator operation, but the torque production capability is limited as speed increases
Solution Approach 1:
The patent modifies the electrical parameters of the BLDC machine by changing the winding configuration and magnet arrangement to achieve a back-emf constant within 25%-75% of nominal battery voltage, optimizing the balance between voltage generation and torque production capabilities
2Use of energy by moving object
If the BLDC machine operates at high speeds as an alternator, then sufficient electrical energy can be generated, but large back-emf voltage induces large short-circuit current leading to heat generation
Solution Approach 1:
The patent optimizes the machine's electrical parameters including winding inductance and back-emf constant to reduce short-circuit current magnitude, thereby minimizing I²R losses and heat generation in both stator windings and power switches during alternator operation
3Ease of operation
If position sensors and wiring harness are used for optimal commutation, then precise control of the BLDC machine is achieved, but the system becomes vulnerable to failures due to high temperature and vibration
Solution Approach 1:
The patent removes the position sensors and related wiring harness from the system, implementing sensor-less operation using electrical signal-based position estimation methods that eliminate the vulnerable mechanical sensing components while maintaining commutation control
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
The solution results in higher torque production at higher speeds, reduced short-circuit current for increased efficiency, and favorable conditions for sensor-less operation, enhancing the ISG system's starting and generating performance while minimizing heat generation in the Electronic Control Unit.
Implementation Method 1
the back-emf constant of the electric machine is substantially between 25% of a nominal battery voltage and 75% of the nominal battery voltage
Implementation Method 2
The electric machine further has a rotor with 4n rotor poles facing the stator, magnets on the rotor poles being disposed with an alternating sequence of magnet polarity facing the stator
Implementation Method 3
The line currents result in heat generation in stator winding of the BLDC machine because of resistance of stator winding
Implementation Method 4
the line currents result in heat generation inside the ECU because of the resistance of power switches
Data Source
AI summary
An Integrated Starter Generator system (100) comprising a battery (110) and a three-phase brushless DC electric machine (130). The electric machine (130) has a stator (132) with 3n stator teeth (132′), ‘n’ being a natural number, and each stator tooth (132′) has a coil corresponding to one of the three phases. The electric machine (130) further has a rotor (134) with 4n rotor poles (134′) facing the stator (132), and magnets on the rotor poles (134′) are disposed with an alternating sequence of magnet polarity facing the stator (132). Herein, back-emf constant of the electric machine (130) is substantially between 25% of a nominal battery voltage and 75% of the nominal battery voltage.