IPMSM Rotor Bridge Positioning for High-Speed Torque Retention
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Solution Overview
Problem
Interior permanent magnet synchronous motors (IPMSM) require high voltage for high-speed operation due to counter electromotive force, leading to torque reduction when field weakening operation exceeds the optimum advance angle.
Innovation Solution
A rotary electric machine design with a stator and rotor featuring specific placement of permanent magnets, flux barriers, and bridges that optimize the circumferential positions of bridge ends to enhance magnetic flux transmission, allowing for high torque output while reducing voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If field weakening operation is performed to reduce voltage in high-speed operation region, then voltage requirement is reduced, but torque decreases
Solution Approach 1:
The invention changes the geometric parameters of the rotor structure, specifically the circumferential positions of the front and rear ends of the first bridge relative to the permanent magnets. By optimizing these positions (with the front end of the rear bridge positioned θf radians ahead of the rear reference location and the rear end of the front bridge positioned 0 to θf radians ahead of the front reference location), the magnetic flux transmission is enhanced, allowing the motor to maintain higher torque in the field weakening region while operating at reduced voltage.
2Use of energy by moving object
If advance angle is increased beyond optimum advance angle to reduce voltage, then voltage is reduced, but torque rapidly decreases
Solution Approach 1:
The invention modifies the rotor's magnetic circuit geometry by positioning the first bridge ends at specific circumferential locations. This structural parameter change allows the motor to operate effectively at larger advance angles (beyond the conventional optimum) without experiencing rapid torque degradation, thereby enabling voltage reduction while maintaining torque performance.
Solution Approach 2:
The optimized bridge positioning is designed in advance to pre-compensate for the torque loss that would normally occur in the field weakening region. By structurally preparing the magnetic flux paths before operation, the motor can withstand larger advance angles and operate at reduced voltage without torque penalty.
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 design improves torque performance by optimizing the circumferential positions of bridge ends, enabling high torque output with reduced voltage, thus addressing the torque reduction issue in high-speed operations.
Implementation Method 1
an interior permanent magnet synchronous motor (IPMSM) of this type is operated by utilizing a magnetic flux of a permanent magnet
Implementation Method 2
a rotary electric machine including: a stator having an annular shape; and a rotor that is disposed in the stator, in which the rotor includes: a rotor core; and a plurality of sets of permanent magnets embedded in the rotor core
Implementation Method 3
the rotor core includes: a first flux barrier provided on both sides in a rotation direction of the rotor with respect to each set of the permanent magnets; and a first bridge provided outside the rotor core in a radial direction with respect to the first flux barrier
Implementation Method 4
the rear end of the front bridge and the front end of the rear bridge are portions of the bridges where magnetic saturation of the magnetic flux generated by each set of permanent magnets occurs
Data Source
AI summary
When a front reference location (Pf) is an intersection point of a front imaginary line (L1) passing through a center axis (O) of a rotor core (31) and a front end of a front magnet (32f) and an outer circumferential surface of the rotor core (31) in a plane view, and a rear reference location (Pr) is an intersection point of a rear imaginary line (L2) passing through the center axis (O) of the rotor core (31) and a rear end of a rear magnet (32r) and the outer circumferential surface of the rotor core (31) in the plane view, a front end of a rear bridge (39r) is disposed at a position away from the rear reference location (Pr) to a front (F) by θf (radian) at a central angle about the center axis (O), and a rear end (39f1) of a front bridge (39f) is disposed at a position away from the front reference location (Pf) to the front (F) by 0 (radian) or more and θf (radian) or less at the central angle about the center axis O. However, θf satisfies Formulae (1) and (2) described below.0<θf≤(θa/8)(1)θa=2π/(Nslot)(2)