Universal Motor Oil Compressor Starting Torque
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Solution Overview
Problem
Typical induction motor-driven oil-lubricated compressors face difficulties in starting and re-starting due to low torque values and require high current, leading to breaker tripping issues, especially in cold weather or low voltage conditions.
Innovation Solution
The use of a universal motor with a brushed or brushless design, featuring electrographite grade brushes and an improved commutator design, which generates higher torque at lower amperage and can start and re-start at lower voltages, overcoming the viscosity of lubricating oil and preventing breaker tripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If an induction motor is used to drive the compressor pump, then the motor can provide continuous running torque, but the starting torque is insufficient to overcome the viscosity of lubricating oil, resulting in difficulty starting and re-starting
Solution Approach 1:
The patent changes the motor type from induction motor to universal motor, which fundamentally alters the torque-voltage characteristics. The universal motor provides high starting torque at low voltages due to its series-wound construction, where both field and armature currents are equal and vary together, creating strong magnetic fields during startup when the compressor pump resistance is highest.
2Force
If an induction motor is used to deliver sufficient starting torque, then high current (100 amps or greater) is required, but this causes breakers to trip on the compressor or in the electrical panel
Solution Approach 1:
The universal motor changes the current-torque relationship by using series winding configuration where field and armature currents are identical and both increase together during startup. This allows the motor to develop high torque at moderate current levels (e.g., 30-50 amps) rather than requiring 100+ amps, preventing breaker tripping while maintaining starting capability.
3Reliability
If an induction motor is used, then the motor struggles to start under low voltage conditions, but providing higher voltage to ensure starting increases the risk of tripping breakers
Solution Approach 1:
The universal motor's series-wound design creates a nonlinear torque-voltage relationship where torque is proportional to the square of the voltage. This means the motor maintains high starting torque even at reduced voltages (e.g., 110V or 220V) without requiring voltage boosts that would trigger breakers, as the high resistance of the compressor pump at startup naturally limits current draw.
4Force
If an induction motor is used, then the motor fails to overcome oil viscosity in cold weather, but increasing power consumption to compensate for cold weather increases current draw and breaker tripping risk
Solution Approach 1:
The universal motor provides high torque at low power consumption during cold weather startup due to its series-wound configuration. The motor's ability to generate strong magnetic fields with moderate current allows it to overcome increased oil viscosity without requiring excessive power, maintaining efficient operation across temperature variations.
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
The universal motor-driven compressor achieves a long operating life of 300-600 hours, starts and re-starts efficiently at low voltages, and operates effectively in cold weather without tripping breakers, providing high torque at low amperage and reducing inrush current.
Implementation Method 1
The universal motor has a torque generated from a field in the armature of the motor that is created through direct contact with the armature and/or the commutator through a brush system
Data Source
AI summary
An oil lubricated compressor having a universal motor, efficient starting and re-starting characteristics, and a long operating life. The oil lubricated compressor can have a brushed or brushless universal motor which can drive a cooling fan and a pump. The universal motor can achieve a high torque to voltage ratio, as well as a high torque to current ratio, upon starting or re-starting of the compressor. Optionally, the oil lubricated compressor can use a single cooling fan disposed in the compressor at a location which is between the universal motor and a cylinder head of the pump.