Electric Motor Ironless Rotor Sensorless Control
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Solution Overview
Problem
Existing electric motor technologies face challenges in efficiently controlling mechanical speed at low speeds and preventing iron losses, particularly in synchronous motors with iron cores, and require complex control measures for field-oriented control.
Innovation Solution
The method involves detecting or estimating mechanical speed to determine the stator supply frequency, reducing it below a minimum frequency, and using a hysteresis-prone characteristic curve to maintain frequencies above zero, allowing for sensorless control and ironless rotor designs with multilayer printed circuit board windings, eliminating the need for mechanical commutators and reducing iron losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If field-oriented control is implemented in synchronous motors with iron cores, then control precision is improved, but iron losses increase due to hysteresis-prone characteristic curves
Solution Approach 1:
The patent extracts the iron cores from the rotor design, creating an ironless rotor structure. This eliminates the hysteresis losses associated with iron cores while maintaining the field-oriented control capability. The rotor winding is directly mounted on the rotor body without an iron core, thereby removing the source of iron losses.
Solution Approach 2:
The patent changes the magnetic circuit parameter by eliminating the iron core material from the rotor. This fundamental parameter change transforms the magnetic circuit from one with high permeability and hysteresis losses to one with air as the magnetic path material, which has no hysteresis losses.
2Device complexity
If mechanical commutators are used in DC motors, then simple control structure is achieved, but mechanical wear and maintenance requirements increase
Solution Approach 1:
The patent replaces the mechanical commutator system with an electronic commutation system using inverters and control electronics. The rotor winding is fed by a rotor-side inverter that electronically switches current phases, eliminating mechanical contact and commutator wear while achieving precise commutation control.
Solution Approach 2:
The patent introduces control electronics and inverters as intermediary devices between the power source and the rotor winding. These electronic intermediaries perform the commutation function that was previously handled mechanically, providing wear-free and maintenance-free operation.
3Loss of energy
If rotor feed frequency is reduced to zero for iron loss reduction, then power losses decrease, but control stability deteriorates due to open integrations diverging
Solution Approach 1:
The patent maintains continuous electrical excitation of the rotor winding through the rotor-side inverter, even at zero or low speeds. This continuous action provides a stable reference for control algorithms and prevents integration divergence, while the ironless rotor design ensures no iron losses occur during this continuous excitation.
4Ease of manufacture
If iron cores are provided on both stator and rotor sides, then magnetic flux guidance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the iron core from the rotor side while retaining it on the stator side. This selective removal simplifies rotor manufacturing and eliminates rotor iron losses, while the stator iron core continues to provide effective magnetic flux guidance for the motor operation.
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 approach enhances control dynamics, reduces power losses, and enables efficient operation at low speeds without feedback integrators, simplifying control and eliminating iron losses in both stator and rotor.
Implementation Method 1
a winding, in particular a rotor winding, being arranged on the rotor, which is designed as a rotating field winding
Implementation Method 2
the mechanical speed of the rotor relative to a stator... the rotational speed of the rotor
Implementation Method 3
the characteristic curve represents a hysteresis-prone dependence of the electrical frequency ωS,Soll on the mechanical speed
Data Source
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AI summary
The invention relates to a method for operating an electric machine and to an electric motor for carrying out said method, wherein a rotor winding at the rotor is designed as a rotary field winding, and wherein a stator winding is arranged on the stator, which is also designed as a rotary field winding, wherein each rotary field winding is fed from a respective inverter and wherein, on the basis of the mechanical speed and according to a characteristic curve, an electrical frequency ωS, Soll is determined from the voltage that is fed from the inverter on the stator side to the stator winding. According to the invention, the characteristic curve is formed such that the stator feed frequency is reduced to less than a minimum frequency in a rotational speed range from at least Ωmin to Ω0, wherein Ωmin is a first rotational speed and Ω0 is a second rotational speed, the amount of the second rotational speed Ω0 being greater than the amount of the first rotational speed.