Design of a controllable resistor load bank

Abstract

This research is focused on designing a controllable, dry type resistor load bank for load testing purpose and developing a model to simulate the load controlling techniques in modern load banks.

A literature review was carried out on the types of load banks and their applications. The operation and the drawbacks of the liquid type load bank, which is commonly used in industry, are discussed by studying the generator load testing procedure at Colombo Dockyard PLC (CDPLC). This addresses the practical difficulties, operational issues and limitations encountered in the generator load testing procedure.

A study has been done on the main components in a modern dry type load bank, including the selection method of power resistors and their special construction features. The variation of resistance values with the temperature is discussed in detail.

Different load controlling techniques available in modern load banks are discussed and a MATLAB Simulink Model is developed to simulate the automatic load controlling with the variation of temperature in a linearly switched load bank with PWM tailing.

A detail design proposal of a dry type load bank, from the capacity selection to design stage, including ratings, resistor composition, arrangement, resistor selection, cooling design, power circuit design, control safety and indication designs is given considering the requirement of generator load testing at CDPLC. A Bill of Material is given for the major components used in the implementation stage. An economic analysis on the proposed load bank was done in comparison with the present load testing procedure by conducting a case study with actual test data and major cost components obtained from a recently completed ship building project at CDPLC.

The advantages and the economical aspects of the design proposal were discussed presenting the limitations and further improvement opportunities.