Switched Reluctance Motor Inverter with Segmented Capacitor Design
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Solution Overview
Problem
Existing frequency converters for switched reluctance motors are complex and costly due to the need for high-capacity smoothing capacitors to filter harmonics, which also require additional components for regenerative power supply and energy storage.
Innovation Solution
A frequency converter design with a capacitor connected between the DC link's positive pole and the output of the freewheeling diode, allowing commutation energy storage and release, and a passive mains filter with an inductor and capacitor to reduce high-frequency harmonics, using field-effect transistors for efficient switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high-capacity smoothing capacitor is used to filter harmonics and maintain constant intermediate circuit voltage, then power yield and motor performance are improved, but device complexity and cost increase due to additional components and larger capacitor size
Solution Approach 1:
The patent divides the energy storage function into two separate components: a first capacitor for commutation energy and a second capacitor for smoothing. This segmentation allows each capacitor to be optimized for its specific function, reducing the total capacity needed compared to a single large capacitor, thereby simplifying the overall device while maintaining power yield.
Solution Approach 2:
The patent introduces a temporal dimension to energy storage by using two capacitors with different time constants. The first capacitor handles high-frequency commutation energy with fast switching, while the second capacitor handles low-frequency voltage ripple with slower response. This multi-timescale approach reduces the total energy storage capacity needed while maintaining stable operation.
2Power
If a smoothing capacitor is used to maintain constant intermediate circuit voltage, then motor performance is improved, but manufacturing cost increases due to larger capacitor capacity requirements
Solution Approach 1:
The patent segments the capacitor system into two functional units: a first capacitor specifically for commutation energy storage and a second capacitor for voltage smoothing. This allows each capacitor to be sized appropriately for its specific function rather than requiring one oversized capacitor, reducing manufacturing costs while maintaining motor performance.
Solution Approach 2:
The first capacitor serves dual purposes: it stores commutation energy during switching operations and simultaneously contributes to voltage smoothing. This multi-functionality reduces the total capacitor capacity needed, lowering manufacturing costs while maintaining stable intermediate circuit voltage for optimal motor performance.
3Reliability
If regenerative power supply components are added to store commutation energy, then switching reliability is improved, but device complexity and component count increase
Solution Approach 1:
The patent merges the commutation energy storage function with the voltage smoothing function by using the first capacitor to serve both purposes. This consolidation eliminates the need for separate regenerative power supply components, reducing device complexity and component count while maintaining switching reliability through adequate energy buffering during commutation events.
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 design results in a simpler, cost-effective, and reliable frequency converter capable of high-speed operation with reduced component count and efficient harmonic filtering, suitable for high-speed switched reluctance motors.
Implementation Method 1
a buffer store for storing commutation energy due to charge reversal processes in the phase winding
Implementation Method 2
a rectifier for generating or converting an AC voltage (UN) on the mains side into a rectified voltage in an intermediate circuit
Implementation Method 3
at least one controlled switch for energizing at least one phase winding of an electric motor, which is fed from the DC voltage intermediate circuit
Implementation Method 4
a freewheeling diode associated with the phase winding for decoupling commutation energy
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The converter (1) has a rectifier (B1) provided for converting alternating current (UN) into an intermediate circuit direct current. An intermediate buffer is designed as a capacitor (Cdump) connected between a positive pole (9) of a direct current-intermediate circuit (7) and an output of free-wheeling diodes (D1, D2). A switch (Tgem) is designed to bridge the capacitor at time intervals such that discharge of the capacitor takes place by activated phase windings (Ph1, Ph2) of an electric motor. The capacitor stores communication energy based on a charging process in the phase windings. An independent claim is also included for a mechatronic system comprising a reluctance motor.