Permanent Magnet Compressor Motor Star-Delta Speed Switching
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Solution Overview
Problem
Existing compressor motor designs often result in low comprehensive efficiency, small expansion range, and poor user experience due to inadequate parameter design, particularly in switching between star and triangle connections.
Innovation Solution
A compressor with a permanent magnet motor connected to a frequency converter, where the critical rotation speed and connection mode are optimized to ensure high efficiency at both low and high speeds, using a relationship between back-EMF coefficient, number of poles, direct axis inductance, output current, and busbar voltage to maintain performance across the frequency band, with a selector switch for smooth mode switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the motor design parameters are not properly optimized, then the motor can operate at different speeds, but the comprehensive efficiency is low and the expansion range is small
Solution Approach 1:
The patent implements dynamic switching between star and triangle winding connections based on operating speed. The motor automatically transitions from star connection at low speeds to triangle connection at high speeds, optimizing efficiency across the entire operating range. This dynamic adaptation resolves the contradiction by making the motor's electrical configuration responsive to speed conditions rather than fixed.
Solution Approach 2:
The patent changes key motor parameters including the switching speed threshold n0 (set to ≥40 r/s), the preset speed n1 (set to 0.95-1.05 times n0), and the relationship parameters (E0, P, I1, Ld, Udc) to optimize performance. By carefully adjusting these parameters, the motor achieves high efficiency across both low and high speed ranges, expanding the effective operating range while maintaining energy efficiency.
2Adaptability or versatility
If the winding connection is switched between star and triangle, then the speed range expands, but the switching impact affects stability
Solution Approach 1:
The patent performs preliminary optimization of the switching threshold n0 and preset speed n1 before actual operation. By setting n0 ≥ 40 r/s and n1 within 0.95-1.05 times n0, the system prepares optimal switching points in advance. This preliminary configuration ensures that when switching occurs during operation, the impact is minimized and stability is maintained, as the switching parameters have been pre-optimized to avoid problematic operating regions.
3Productivity
If the motor operates at both low and high speeds efficiently, then the product performance improves, but the parameter design complexity increases
Solution Approach 1:
The patent creates a universal control strategy that handles both low-speed and high-speed operations through a unified parameter set. The same switching threshold n0 and preset speed n1 relationships work across the entire operating range, making the control system multi-functional rather than requiring separate optimization for each speed range. This universality improves overall product performance while avoiding the complexity of multiple independent control systems.
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 enhances the compressor's efficiency and performance by ensuring high efficiency at low and high speeds, reducing the impact of mode switching, and improving energy efficiency and market competitiveness.
Implementation Method 1
a no-load back-electromotive force (back-EMF) coefficient of the permanent magnet motor is E0
Data Source
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AI summary
This present application provides a compressor and a refrigeration device, wherein, the compressor for a refrigeration device, the refrigeration device comprising a coupling assembly and a frequency converter connected to one end of the coupling assembly, wherein the compressor comprises: a first shell; and a permanent magnet motor being set in the first shell and connected to the other end of the coupling assembly; acritical rotation speed of the permanent magnet motor is n0; a number of poles of the permanent magnet motor is P; when a winding of the permanent magnet motor is in star connection, a busbar voltage of the frequency converter is Udc, a no-load back-EMF coefficient of the permanent magnet motor is E0, when a preset rotation speed of the permanent magnet motor is n1, a direct axis inductance of the permanent magnet motor is Ld, and an output current of the frequency converter is I1, a relationship between the E0, the P, the I1, the Ld, the n1, and the Udc satisfies (EO - P × I1 × Ld) × n1 ≥ 0.6 Udc, wherein n1 < n0, and n0 - n1 ≤ 1 r/s, when a winding of the permanent magnet motor is in star connection, a rotation speed of the permanent magnet motor is less than the n0.