Synchronous Motor Winding Turns for Torque-Power Balance
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Solution Overview
Problem
Rotary electric machines for self-propelled mobile devices face challenges in optimizing torque and mechanical power across varying speeds, with existing designs experiencing significant torque drop at high speeds and insufficient power at low speeds, due to fluctuating voltage requirements and size constraints.
Innovation Solution
The solution involves optimizing the number of turns per phase in the stator winding of synchronous electric machines, ranging between 9 and 20, to balance torque and power delivery across speed ranges, while minimizing inverter-rectifier current and size, by adjusting the number of conductors and slots to accommodate voltages between 48 volts and 600 volts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the number of turns per phase is increased to improve low-speed torque, then high-speed power capability deteriorates due to excessive inductance and current limitation
Solution Approach 1:
The patent applies parameter changes by optimizing the number of turns per phase to a specific range (9-20 turns) rather than using conventional higher values. This parameter optimization balances the inductance value to maintain both low-speed torque and high-speed power capability, resolving the contradiction between torque and power across the speed range.
2Power
If the number of turns per phase is decreased to improve high-speed power, then low-speed torque capability deteriorates due to insufficient inductance
Solution Approach 1:
The patent establishes a minimum threshold of 9 turns per phase to ensure sufficient inductance for low-speed torque generation while allowing the upper limit of 20 turns to prevent excessive inductance that would limit high-speed power. This parameter range optimization simultaneously satisfies both low-speed and high-speed performance requirements.
3Volume of moving object
If the machine size is reduced to meet vehicle integration constraints, then thermal management capability deteriorates due to reduced volume for heat dissipation
Solution Approach 1:
The patent optimizes the number of turns per phase to reduce copper losses and improve efficiency, which generates less heat for a given power output. This allows compact machine design with reduced volume while maintaining acceptable thermal management through lower heat generation rather than relying solely on increased cooling volume.
4Area of stationary object
If the number of turns per phase is increased to reduce inverter-rectifier current, then manufacturing complexity increases due to more stringent winding requirements
Solution Approach 1:
The patent identifies an optimal range of 9-20 turns per phase that reduces the current rating requirements for the inverter-rectifier, allowing for more compact power electronics design. This moderate turn count also maintains manufacturability by avoiding excessive winding complexity that would result from much higher turn counts, thus balancing both inverter size reduction and manufacturing ease.
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 optimization results in a balanced synchronous machine with optimal torque and mechanical power for a given size, maintaining power synchronization from low to high speeds, and reducing thermal issues, ensuring efficient operation across the speed range.
Implementation Method 1
the rotor is provided with permanent magnets and the stator with an electrical winding. The rotor and the stator form an electric motor and interact via a magnetic field.
Implementation Method 2
the rotation of the rotor equipped with excitation coils or magnets generates a rotating magnetic field at the electrical winding of the stator
Data Source
AI summary
A permanent-magnet synchronous rotary electric machine for a self-propelled mobile device includes a stator having slots and a winding including at least three phases. The winding is of the type in which the number of turns N in the stator per phase is equal to the number of conductors in a slot, multiplied by the number P of pole pairs multiplied by the number of slots per pole and per phase, all divided by the number of parallel electrical paths of the conductors in a slot and/or divided by the square root of three if the winding is delta-coupled. The number of turns N per phase in the stator is between 9 and 20.