Introduction to Motor Starting Analysis
Author: Velimir Lackovic
The starting current of most AC motors is several times normal full load current. Both synchronous and induction motors can draw five to ten times full load current when starting them across the line. Motor-starting torque varies directly as the square of the applied voltage. If the terminal voltage drop is excessive, the motor may not have enough starting torque to accelerate up to running speed. Running motors may stall from excessive voltage drops, or under-voltage relays may operate. In addition, if the motors are started frequently, the voltage dip at the source may cause objectionable flicker in the lighting system.
By using motor-starting study techniques, these problems can be predicted before the installation of the motor. If a starting device is needed, its characteristics and ratings can be easily determined. A typical digital computer program will calculate speed, slip, electrical output torque, load current, and terminal voltage data at discrete time intervals from locked rotor to full load speed. Also, voltage at important locations throughout the system during start-up can be monitored. The study can help select the best method of starting, the proper motor design, or the required system design for minimizing the impact of motor starting on the entire system.
This course presents an introduction to the methods and procedures used in the analysis of motor starting. It includes numerous diagrams and waveforms to demonstrate how large motors are started in large industrial systems.
Once you complete your course review, you need to take a multiple-choice quiz consisting of forty (40) questions to earn 4 PDH credits
This course is intended to provide you with the following specific knowledge and skills:
- Need for motor starting studies
- Motor starting techniques
- Types of studies
- Data requirements
- Motor modelling for the purpose of power system studies
- Solution procedures and examples
Download the Course to review and begin earning your PDH credits.
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