PM Rotor Carrier Frequency Control for Eddy Current Loss
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Solution Overview
Problem
Conventional rotary electric machines with eddy current suppression members at the outer peripheries of permanent magnets still experience increased eddy current loss due to current flow through both the magnets and the suppression members, particularly under certain control conditions.
Innovation Solution
A permanent magnet-type rotary electric machine driving system that includes a control device setting a carrier frequency higher than a calculated frequency based on specific formulae to suppress eddy current loss by optimizing the arrangement and conductivity of eddy current suppression members with insulating members interposed, reducing eddy current flow in both the magnets and suppression members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If eddy current suppression members with high conductivity are used, then eddy current suppression effectiveness is improved, but eddy current loss in the suppression members increases under certain control conditions
Solution Approach 1:
The patent resolves this contradiction by changing the operating frequency parameter to be higher than the calculated frequency f. At these higher frequencies, the eddy current loss in the high-conductivity suppression members is reduced due to skin effect and other high-frequency phenomena, allowing the suppression members to maintain their effectiveness without excessive energy loss.
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 system effectively suppresses eddy current loss in the entire rotor by driving at frequencies higher than the loss cross frequency, thereby minimizing temperature increase and power loss in the permanent magnets.
Implementation Method 1
eddy current flows through permanent magnets during rotational operation. When eddy current flows through the permanent magnets, resistance increase and temperature increase of the permanent magnets occur due to the eddy current
Implementation Method 2
an inverter which outputs driving power to the stator coil; and a control device which designates a carrier frequency for the inverter
Data Source
AI summary
An object is to drive a permanent magnet-type rotary electric machine including eddy current suppression members, under such a control condition that can suppress eddy current loss in an entire rotor. A permanent magnet-type rotary electric machine driving system includes: a permanent magnet-type rotary electric machine including a stator having a stator core and a stator coil, and a rotor having a rotor core, a plurality of permanent magnets, and eddy current suppression members; an inverter; and a control device for designating a carrier frequency. The control device designates the carrier frequency greater than a loss cross frequency calculated from formulae using dimensions and physical constants of the permanent magnets and the eddy current suppression members.