Explosion-proof Motor End Shield Flame Path Gap Design
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Solution Overview
Problem
Existing explosion-proof electric motors face limitations in size reduction and bearing selection due to minimum flame path length requirements, which restrict the use of larger bearings and increase vibration, while traditional assembly methods hinder the passage of inner bearing caps through the stator bore.
Innovation Solution
The design incorporates a flame path gap between the end shield and inner bearing cap, featuring both radial and axial sections, allowing for a smaller bearing cap diameter while maintaining the required flame path length, enabling the use of larger bearings on both ends of the motor and facilitating their secure locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional radial flame path gap is used between end shield and bearing cap, then the flame path length requirement is met, but the bearing cap diameter must be large which prevents passage through stator bore and limits bearing size selection
Solution Approach 1:
The flame path gap is configured to include both a radial section and an axial section, transitioning from a purely radial arrangement to a multi-dimensional arrangement. This allows the flame path length to be extended in the axial direction while keeping the bearing cap diameter smaller, enabling passage through the stator bore.
Solution Approach 2:
The flame path gap is divided into multiple sections: a radial section and an axial section. This segmentation allows the total flame path length to be achieved through combined radial and axial distances rather than requiring a large radial distance alone, thus reducing bearing cap diameter.
2Reliability
If minimum flame path length is maintained with traditional configuration, then explosion-proof certification is achieved, but motor size reduction is prevented and bearing size options are limited
Solution Approach 1:
By utilizing both radial and axial dimensions for the flame path gap, the design achieves the required flame path length without constraining bearing size selection. Larger bearings can be used on both ends of the motor while still meeting certification requirements.
3Reliability
If larger bearings are used to reduce vibration and increase load capacity, then motor performance is improved, but the bearing cap becomes too large to pass through stator bore during assembly
Solution Approach 1:
The axial section of the flame path gap allows larger bearings to be used for reduced vibration and increased load capacity, while the multi-dimensional configuration enables the bearing cap to pass through the stator bore during assembly by reducing the required diameter.
4Ease of manufacture
If bearing cap diameter is reduced to enable passage through stator bore, then assembly is facilitated, but flame path length requirement may not be met
Solution Approach 1:
The flame path gap incorporates both radial and axial sections, allowing the bearing cap diameter to be reduced for easy assembly while the total flame path length requirement is maintained through the combined radial and axial distances.
Solution Approach 2:
The flame path gap is segmented into radial and axial portions, enabling the bearing cap to be smaller for easy assembly while the total flame path length is achieved through the combined length of both segments.
Data Source
AI summary
An explosion proof motor including a stationary assembly and a rotatable assembly is described. The stationary assembly includes a stator that defines a stator bore. The rotatable assembly includes a rotor and a rotor shaft extending substantially axially through the stator bore. The explosion proof motor includes a frame configured to at least partially surround the stator. The frame defines an interior and an exterior of the motor. The explosion proof motor also includes at least one end shield positioned at an end of the frame and a bearing cap positioned proximate to the interior side of the end shield. The explosion proof motor also includes a flame path gap defined between the end shield and the bearing cap. The flame path gap includes at least one section that extends substantially parallel to the rotor shaft.