Jim Bryan (deceased)
Technical Support Specialist
Electrical Apparatus Service Association, Inc.
St. Louis, MO
The paper "Connections for Winding & Starting" by Jim Bryan, presented at the EASA Convention 2015, provides a comprehensive overview of the various methods used to design and implement motor winding connections. The paper emphasizes the importance of understanding the nuances of winding design and connection to ensure efficient and reliable motor operation. It primarily focuses on NEMA designations, although IEC standards are briefly mentioned.
Bryan begins by explaining the significance of the sine wave in three-phase electrical power, highlighting the role of the square root of three (√3) in power calculations. He compares single-phase and three-phase power, demonstrating the efficiency advantages of three-phase motors. The paper then delves into the numbering conventions for motor coil ends, providing detailed diagrams for wye and delta connections.
The discussion moves to the relationship between coil, phase, and line voltage, emphasizing the importance of √3 in determining voltage and current values for wye and delta connections. Bryan provides clear illustrations to show how these connections are made and the resulting voltage and current relationships.
The paper covers various external connections and ladder diagrams, starting with the simplest form of single voltage wye and delta connections. Bryan explains dual voltage motors, which use nine leads to configure the winding in series or parallel for different voltage levels. He provides detailed diagrams for dual voltage wye and delta connections, highlighting the importance of correct connections to avoid motor failure.
Bryan discusses across the line (ACL) starting, reduced voltage starters, and part winding start (PWS) motors. He explains the NEMA MG1 standards for part winding starting, noting the potential issues with insufficient torque and the importance of incremental starting current. The paper includes ladder diagrams for PWS motors and various starting methods, such as wye start-delta run and double delta or extended delta part winding start.
The paper also covers motors designed for multiple speeds, including two distinct speeds with two windings and one winding with high and low speed configurations. Bryan explains constant horsepower, constant torque, and variable torque connections, providing detailed diagrams for each.
Parallel circuits are discussed as a means to accommodate different applications and voltages. Bryan provides examples of parallel circuit configurations and the impact on motor performance. He also addresses odd connections, such as tri-voltage and single voltage wye-delta or part winding start motors.
The paper concludes with a discussion on jumper selection, explaining the difference between adjacent-pole (1-4) and skip-pole (1-7) jumpers. Bryan emphasizes the importance of correct jumper selection to avoid circulating currents and ensure balanced magnetic forces.
Key Points Covered:
- Importance of sine wave and √3 in three-phase power
- Numbering conventions for motor coil ends
- Relationship between coil, phase, and line voltage
- External connections and ladder diagrams for various starting methods
- Dual voltage motors and correct connection practices
- Part winding start (PWS) motors and NEMA MG1 standards
- Multiple speed motors and their configurations
- Parallel circuits and their impact on motor performance
- Odd connections and their applications
- Jumper selection and its importance
Key Takeaways:
- Understanding winding design and connection is crucial for efficient and reliable motor operation.
- Correct connections are essential to avoid motor failure and ensure proper voltage and current relationships.
- Various starting methods and configurations can be used to accommodate different applications and voltages.
- Parallel circuits offer flexibility but require careful consideration to avoid excessive voltage between coils.
- Jumper selection is important to ensure balanced magnetic forces and avoid circulating currents.
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