Motor Starting Studies

What are Motor Starting Studies?

• Improper motor starting can damage the motor, create disturbance to the locally connected loads and buses, power quality issues, and service interruptions. Therefore, motor starting studies are recommended before installation.

• The objective of motor starting studies is to check whether the motor can be started successfully under various operating conditions.

• This study investigates the load, motor and acceleration torque, bus voltage (voltage drop), motor starting current, acceleration time, power factor, and motor slip.

• Motor starting studies are required if the motor horsepower rating exceeds 30% of the base kVA rating of the supplying transformer or 10% to 15% of the generator kVA rating (no transformer case).

What is the Importance of Motor Starting Studies?

The main purpose of motor starting studies is to verify that:

• • The motor can be started within the acceptable voltage drop and it will not affect other loads.

  • The motor can be started within the acceptable start-up time.

  • The speed-torque and thermal characteristics of the motor are evaluated correctly.

  • The motor feeders are properly sized.

  • The Protection device for the motor is set properly such that the motor will not trip during start-up.

  • Identifying the type and size of the starter/drive to start the motor.

How Do We Perform Motor Starting Studies?

• Step-1: Data collection such as single line diagram (SLD), data sheet of all the equipment, bus and branches, synchronous and induction motors, synchronous generators, transformers, transmission lines/cables, load characteristics, motor operated valve (MOV), capacitor banks, variable frequency drive (VFD), lumped loads, etc.

• Step-2: Modeling the study system/substation using ETAP or PSS®E or PSCAD/EMTDC software.

• Step-3: Preparation of simulation case studies with the study scenarios accepted by clients.

• Step-4: Preparation of technical report and submission to clients.

What Standards can be Referred for Motor Starting Studies?

• IEEE Std 3002.7™-2018 - IEEE Recommended Practice for Conducting Motor-Starting Studies and Analysis of Industrial and Commercial Power Systems.

• IEEE Std 399-1997 - IEEE Recommended Practice for Industrial and Commercial Power Systems Analysis.

• IEC 60034 (Series) - Rotating Electrical Machines

• ANSI/NEMA MG 1-2021 – Motors and Generators.