Starter Generator Winding Segmentation for Power Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing starter generator configurations face issues with power loss, increased fuel inefficiency, and engine friction due to surplus power generation when used as both a starter motor and a power generator, particularly with the use of MOSFETs which do not fully disconnect windings, and are not suitable for delta-connected armature windings, leading to higher costs and complexity.
Innovation Solution
A starter generator apparatus with a configuration that includes two star-connected three-phase coils with separate neutral points, using MOSFETs to bidirectionally convert power and selectively connect/disconnect windings to optimize power generation and load balance, reducing reflux current and heat generation, and allowing for direct mounting on a crankshaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the ACG starter motor is designed with permanent magnet field and armature windings optimized for starter motor torque characteristics, then the starter motor can provide sufficient starting torque, but when used as a power generator, the generated power exceeds the electrical load requirements, causing surplus power and power loss
Solution Approach 1:
The armature windings are divided into multiple independent sets (first armature windings and second armature windings) that can be selectively connected or disconnected. This segmentation allows the system to use only the necessary windings for power generation mode, preventing surplus power generation and reducing power loss while maintaining sufficient torque in starter motor mode.
2Adaptability or versatility
If a relay is used to switch between armature windings for starter motor and power generator modes, then winding selection can be achieved, but the relay contacts experience frequent on/off cycling, leading to contact wear and reduced lifespan
Solution Approach 1:
The mechanical relay switching system is replaced with electronic MOSFET switching elements. MOSFETs provide contactless switching, eliminating mechanical wear and extending system life while maintaining the capability to selectively connect or disconnect armature windings based on operational mode.
3Device complexity
If MOSFETs are used instead of relays to disconnect windings, then contactless switching is achieved, but MOSFETs cannot fully block current in both directions due to parasitic diodes, preventing complete disconnection of the starter motor winding
Solution Approach 1:
Diode bridges are introduced as intermediary components between the MOSFETs and the armature windings. The diode bridges rectify the AC output from the generator windings, converting it to DC, which allows the MOSFETs to effectively control current flow in conjunction with the diode bridge's unidirectional conduction property, achieving complete isolation of the starter motor winding when needed.
4Device complexity
If the armature windings are connected in parallel with common nodes for both starter motor and power generator modes, then the configuration is simplified, but the windings cannot be fully disconnected between modes, leading to excessive power supply and increased power loss
Solution Approach 1:
The armature windings are segmented into independent sets with separate connection points. The first armature windings are connected to first alternate terminals and the second armature windings to second alternate terminals, allowing complete electrical isolation between modes. This segmentation prevents the common node problem and enables full disconnection to eliminate power loss.
5Ease of operation
If the field is constituted with a winding instead of permanent magnets, then brushless operation is achieved, but the apparatus cannot be miniaturized and is not suitable for direct mounting on crankshaft
Solution Approach 1:
Instead of using a wound field with brushes (traditional approach), the patent inverts the approach by using permanent magnets for the field and brushless commutation for the armature windings. This inversion enables miniaturization while maintaining brushless operation, making the apparatus suitable for direct crankshaft mounting.
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 configuration reduces power loss, improves fuel efficiency, and minimizes engine friction by optimizing power generation and load balance, while enabling efficient control characteristics and reduced heat generation in the starter generator.
Implementation Method 1
an orthogonal transformation unit (61) connected to the first winding portion (11), or the winding portion (11) and the winding portion (12), and configured to bidirectionally convert an electric power between a direct current and an alternating current
Implementation Method 2
The ACG starter motor functions as a starter motor at start of an engine
Implementation Method 3
The ACG starter motor functions as a power generator after the start of the engine
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided are: a starter generator including an armature unit including a first winding portion and a second winding portion which are arranged in parallel, each of the first winding portion and the second winding including a polyphase coil, and a field unit including a permanent magnet; an orthogonal transformation unit having a first alternate terminal connected to the first winding portion, and configured to bidirectionally convert an electric power between a direct current and an alternate current; and a plurality of switching elements interposed between the first alternate terminal and the second winding portion, and configured to perform connection and disconnection of the second winding portion to and from the alternate terminal.