EC Motor Commutation via Freewheeling Circuit
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Solution Overview
Problem
Existing electronically commutated motors face inefficiencies due to high voltage peaks during commutation, which require large capacitors with limited lifespan and powerful semiconductor components, leading to reduced motor efficiency and increased material costs.
Innovation Solution
Incorporating an additional controllable semiconductor switch in the supply line to convert stored energy directly into motor torque via a freewheeling circuit, allowing for low-loss commutation and reducing the need for large capacitors and powerful components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an intermediate circuit capacitor is used to absorb stored magnetic energy during commutation, then voltage peaks are limited, but the capacitor size increases and service life decreases due to ripple current and heating
Solution Approach 1:
The patent converts the harmful stored magnetic energy in the phase winding into useful mechanical torque by allowing it to flow through the rotor winding during commutation. This eliminates the need for large capacitors to absorb this energy, thereby extending capacitor service life while maintaining voltage control.
Solution Approach 2:
The patent introduces a freewheeling diode as an intermediary element that provides a controlled path for the stored magnetic energy to flow through the rotor winding. This mediator enables the energy to be converted into useful torque rather than being dissipated as heat or requiring large capacitor absorption.
2Strength
If zener diodes or avalanche energy is used to limit voltage peaks, then voltage control is achieved, but power loss increases and component size must be larger
Solution Approach 1:
Instead of dissipating the stored magnetic energy as heat through zener diodes or avalanche breakdown, the patent redirects this energy through the rotor winding to generate useful mechanical torque. This converts what would be a loss into a beneficial contribution to motor operation.
Solution Approach 2:
The patent replaces the electrical dissipation mechanism (zener diodes converting energy to heat) with an electromechanical conversion mechanism (stored energy driving rotor current and generating torque). This substitution eliminates the power loss associated with resistive dissipation.
3Stability of the object's composition
If large intermediate circuit capacitors are used to handle ripple current, then voltage stability is improved, but material costs increase and motor efficiency decreases
Solution Approach 1:
The patent converts the harmful ripple current that would charge and discharge large capacitors into useful torque by directing the stored phase winding energy through the rotor winding. This eliminates the need for large capacitors and the associated efficiency losses from ripple current.
Solution Approach 2:
The patent recovers the energy that would otherwise be wasted as ripple current by redirecting it through the rotor winding to generate torque. This recovery process eliminates the need for large energy-absorbing capacitors and improves overall system efficiency.
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 motor efficiency, allows for a compact design, and increases power density by converting stored magnetic energy directly into mechanical energy, reducing the requirement for large intermediate circuit capacitors and lessening component stress.
Implementation Method 1
When current flows through a phase winding, energy is stored in it in the form of a magnetic field. The energy that is stored in the phase winding in question before commutation is not converted into heat or temporarily stored in a capacitor, but is used directly to generate torque.
Implementation Method 2
transforming the energy that is stored in the relevant phase winding at the point in time of switching off into a motor torque via a special freewheeling circuit
Data Source
Figure 1
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Figure 3
AI summary
An electronically commutated motor (20) has connections (56, 62) for connection to a DC source (63). It has a permanent-magnet rotor (22), as well as a first and a second series circuit (40, 50) in each of which, respectively, a stator winding section is connected in series with a first and a second controllable semiconductor switch, with the two series circuits being connected in parallel to form a parallel circuit (52). In a supply line to this parallel circuit (52), a third controllable semiconductor switch (60) controls the power supply from the DC source (63) to the motor (20). A control apparatus is designed to carry out the following steps during operation: influenced by the rotation position of the rotor (22), the capability to supply power from the DC source (63) to one winding section is activated during a potential current-flow phase and the capability to supply power to the other winding section is deactivated, alternately, during this potential current-flow phase. In this case, the potential current-flow phase to the one winding section is in each case separated in time by a commutation process from that of the other winding section. The third controllable semiconductor switch (60) is switched off at a switching time (Figure 4: t64) in order to initiate a commutation process, during a potential current-flow phase. The first or second semiconductor switch (34, 44) which is switched on at the switching time (t64) is kept switched on so that, during operation, a circulating current (i31; i31') flows in the parallel circuit (50) during operation after the third semiconductor switch (60) has been switched off and produces a driving torque in the motor, with this circulating current being monitored. When this circulating current reaches a predetermined low absolute value, the first and/or second semiconductor switch that is switched on at that instant is switched off. Depending on the rotation position of the rotor (22), the potential current-flow phase in the one winding section is deactivated, and that in the other winding section is activated, as part of the commutation process, and the third semiconductor switch is switched on again.