Converter for starting motor-generator sets of autonomous locomotives

Objective: To confirm the possibility of using a starting converter to spin up the shaft of the motorgenerator set to a speed that ensures stable combustion of the air-fuel mixture in the motor cylinders (starting), as well as of using semiconductor converters based on modern IGBT modules for starting promising motor-generator sets of mainline and shunting locomotives. Methods: The properties, characteristics, and operating modes of starting converters were studied on test benches. Results: The downsides of the currently most commonly used starter-generator circuit for engine starting have been identified. A technical solution has been developed to replace the startergenerator circuit with an inverter starting system using a starting converter for starting the locomotive motor-generator. The device structure has been designed. The basic algorithms of the automatic control system of the starting converter have been implemented. Bench tests of a starting converter prototype have been carried out. Practical importance: The developed technical solution in terms of replacing the starter-generator circuit with an inverter starting system for starting the motorgenerator set of autonomous locomotives makes it possible to increase their reliability by removing the electromechanical drive and replacing a number of engine drive auxiliary camshaft mechanisms (group 69). The inverter starting system will reduce the maintenance and scheduled repair costs, decrease the labor input, and optimize the time-schedule of locomotives. The proposed algorithms for starting the motor-generator set enable increasing the battery life by limiting its starting current, as well as improving the fault tolerance of a locomotive due to the possibility of starting the motorgenerator set at a low battery voltage (lower limit of 45 V).

Reliability Assessment of Aircraft Commutators

The article describes the method of predicting the reliability and durability of an aircraft commutator, which is a primary source of electric energy in helicopters. Tests were conducted for 10 starter-generators. From this research it follows that the technical condition of brushes and bearings has a significant impact on the reliability of starter-generators. The reliability of starter-generators was determined based on the method consisting of two stages that was adopted: the first stage involved determining the density function of changes in diagnostic parameter depending on the operating time, but the second stage included the assessment of the reliability of bearings of the starter-generator taking into account the real flight profile. The first stage of the adopted method consisted of defining the dynamic model of changing the length of the starter-generator’s brush, which became the probabilistic model. Subsequently, based on differential equations, Fokker–Planck partial differential equation was derived, which describes the process of increasing the brush wear in a probabilistic way. This method enables the prediction of the residual durability of the helicopter’s starter-generator due to the change in a diagnostic parameter which is the wear of brushes during starter-generator operation. The second stage of this method allows determining the durability of starter-generator’s bearings building upon the average helicopter’s flight profile. Owing to the difficulty in measuring the wear of bearings, the relation between the durability of bearings and the temperature of surroundings can be applied by replacing the flight altitude with temperature. The reliability of the helicopter’s starter-generator was determined based on the serial-type reliability structure.

Control Methods for Performance Improvement of an Integrated On-Board Battery Charger in Hybrid Electric Vehicles

This paper presents control methods for performance improvement of an integrated on-board battery charger (OBC) in hybrid electric vehicles (HEVs). HEVs generally consist of an OBC and a starter generator system (SGS). Since these each have a power conversion device for independent operation, such as battery charging and starter generator driving for engine starting, it necessarily increases the number of components, weight, and volume of the HEV. In order to overcome these disadvantages, recent research concerning the integrated OBC has progressed. Although it demands installation of power relays and an additional circuit, the integrated OBC is effectively operated for battery charging and starter generator driving. This paper proposes not only a harmonic reduction method of grid current, but also a feed-forward control method for performance improvement of the integrated OBC in HEVs. The effectiveness of the proposed control methods is verified by simulation and experimental results.