Terminal Block Assemblies for Rotating Electrical Machines
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Solution Overview
Problem
Conventional terminal board assemblies for rotating electrical machines in gas turbine engines, such as aircraft starter generators, face challenges in providing adequate clearance and creepage performance, which can be affected by foreign object debris, leading to potential electrical discharges and tracking issues.
Innovation Solution
A terminal assembly featuring a dielectric terminal block with conductive contacts and locking helical inserts, mounted to an electrical machine housing with o-ring sealing, providing improved mechanical and electrical connections, and including a method of molding conductive terminal contacts into a dielectric block for enhanced insulation and creepage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional terminal board assemblies are used, then the structure is simple, but the creepage distance and strike clearance are insufficient, leading to potential electrical discharges and tracking issues
Solution Approach 1:
The terminal block introduces a vertical dimension (height) to increase creepage distance. The insulating material extends vertically between conductive elements, creating a three-dimensional creepage path rather than a two-dimensional surface path, thereby increasing the effective creepage distance without expanding the horizontal footprint.
Solution Approach 2:
The terminal block employs composite construction combining conductive elements (terminal contacts, lugs) with an insulating material matrix. This composite structure provides both electrical connectivity and electrical isolation, allowing the design to achieve adequate creepage performance while maintaining functional requirements.
2Reliability
If foreign object debris is present near the terminal assembly, then the assembly remains compact, but the clearance and creepage performance are compromised, leading to potential tracking
Solution Approach 1:
The terminal block design preemptively addresses the harmful effect of foreign object debris by providing sufficient clearance and creepage distances that accommodate potential debris accumulation. The insulating material and spacing are designed to maintain electrical isolation even when debris is present, preventing tracking before it can occur.
Solution Approach 2:
The insulating material acts as an intermediary barrier between conductive elements and the external environment. This intermediate layer prevents direct contact between foreign object debris and conductive surfaces, maintaining electrical isolation and preventing debris-induced tracking.
3Reliability
If adequate creepage distance is provided to prevent tracking, then the electrical insulation is improved, but the terminal assembly size increases
Solution Approach 1:
The design utilizes the vertical dimension to achieve adequate creepage distance. By extending the insulating material vertically between conductive elements rather than horizontally, the design maintains compact horizontal dimensions while providing sufficient creepage path length in the vertical direction.
Solution Approach 2:
The terminal contacts and lugs are nested within or alongside the insulating material structure. This nesting arrangement allows the conductive elements to be positioned within the three-dimensional space of the insulating material, maximizing the use of available space while maintaining adequate creepage distances.
Data Source
AI summary
A terminal assembly includes a terminal block of a dielectric material defining a plurality of bores therethrough. A respective terminal contact of an electrically conductive material is seated in each of the respective bores. The terminal contact defines a longitudinal axis therethrough with a terminal bore defined through the terminal contact along the longitudinal axis. A divider wall separates the terminal bore into a solder cup for a lead wire on an interior side of the terminal bore, and a lug receptacle on an exterior side of the terminal bore.