Executive Summary

Large sized motors are utilized in every major industrial facility for performing a variety of functions. But it is critical to know about the consequences of starting large motors on its long term performance along with the adverse effects on the nearby electrical equipment. Smaller facilities are normally supplied power by limited capacity sources, which serve to amplify voltage drop issues on motor-starting, particularly when large motors are involved.

This is where conducting a motor starting study becomes critical, since it is best utilized for analyzing the starting performance of large motors and prevent unnecessary power losses to the facility.

Objective

A motor starting study is used to identify the root cause of voltage dips and deploy mitigation techniques to combat the excessive voltage drops, voltage flickering along with providing effective control of the heavy starting currents.

Brief Study Methodology

Data collection procedures are first performed as per NEC requirements, after which a comprehensive model of the system is developed on power systems software. Calculations are then performed for the voltage drop on each feeder branch, bus, and the projected power flow in the system. A traditional solution or an exact iterative method may be applied based on the data collected and project requirements.

Results are then evaluated with the prescribed limits specified by IEEE standards and the values which exceed the limits are identified and marked. Recommendations based on the analysis performed, are provided to minimize the voltage drops and prevent overheating of the equipment.

Expected Study Outcomes & Recommendations

Motor Starting studies are performed as per the latest IEEE, NEC, ANSI & NFPA standards. Study outcomes and recommendations are expected to improve your facility in the following areas:

• Overall reliability of the system is expected to increase.
• Reduce the impact of load changes on the system.
• Minimize the voltage dips on motors and nearby electrical equipment.
• Minimize the heating losses incurred due to large motors.
• Reduction of excessive running currents.
• Reduction in motor stalling.
• Decrease in the unnecessary tripping of undervoltage relays.

Study Deliverables

The proven expertise of our team of certified professional engineers will aid in the evaluation of your system and deliver state-of-the-art solutions for your power system’s protection. We work closely with our clients in collecting the data, modeling the system, simulating motor starting conditions, plotting the acceleration curves & delivering solutions in compliance with the latest industrial standards.

AllumiaX, LLC provides independent and third-party engineering support by presenting comprehensive deliverable reports backed by industry standards and best practices, analysis work based on industry-leading software (ETAP), and proven results based on accurate modelling and calculations. The reports are expected to include the following deliverables:

• A comprehensive model of the facility in modern power systems software.
• Evaluation of the system for normal and emergency scenarios.
• Accurate models of the motor starting and acceleration curves on log-log plots.
• Identification of the critical areas with voltage drops above standard limits.
• Detailed analysis of the voltage conditions during impact loading.
• Recommendations for minimization of line losses and voltage drops.
• Complete analysis information in a tabular format.

References

• NFPA 70, “National Electric Code” ,2017
• NFPA70E, “Standard for Electrical Safety in the Workplace”, 2017
• IEEE Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems, pp. 493-1997
• A. Jack Williams, “Evaluating the Effects of Motor Starting on Industrial and Commercial Power Systems”, IEEE Transaction on Industry Applications, July 1978
• S. E. Zocholl, “Motor Analysis and Thermal Protection”, IEEE Transactions on Power Delivery, July 1990