Wound Field Synchronous Machine Research Articles

Starting scheme for load commutated inverter-fed wound field synchronous machine using an auxiliary low-power voltage source inverter

Conventional thyristor-based load commutated inverter (LCI)-fed wound field synchronous machine operates only above a minimum speed that is necessary to develop enough back emf to ensure commutation. The drive is started and brought up to a speed of around 10–15% by a complex ‘dc link current pulsing’ technique. During this process, the drive have problems such as pulsating torque, insufficient average starting torque, longer starting time, etc. In this regard a simple starting and low-speed operation scheme, by employing an auxiliary low-power voltage source inverter (VSI) between the LCI and the machine terminals, is presented in this study. The drive is started and brought up to a low speed of around 15% using the VSI alone with field oriented control. The complete control is then smoothly and dynamically transferred to the conventional LCI control. After the control transfer, the VSI is turned off and physically disconnected from the main circuit. The advantages of this scheme are smooth starting, complete control of torque and flux at starting and low speeds, less starting time, stable operation, etc. The voltage rating of the required VSI is very low of the order of 10–15%, whereas the current rating is dependent on the starting torque requirement of the load. The experimental results from a 15.8 hp LCI-fed wound field synchronous machine are given to demonstrate the scheme.

Beyond IEEE Std 115 and API 546: Test Procedures for High-Speed Multimegawatt Permanent-Magnet Synchronous Machines

High-speed multimegawatt permanent-magnet (PM) machines have been proposed in the literature and offered for sale in a variety of petrochemical applications. Presently, the discussion of synchronous machines in both the IEEE Std 115 and American Petroleum Institute 546 excludes the consideration of PM synchronous machines. These machines pose special problems when attempting to apply the test procedures given for the wound-field synchronous machines in that many of the tests rely on the ability to adjust the field strength. In addition, a PM-rotor topology has different performance and robustness concerns than a wound-field machine, and those should be addressed. This paper attempts to outline a coherent method for evaluating high-speed PM machines by extending the test procedures outlined in IEEE Std 115 and presenting additional procedures specific to PM machines. Extended application guidelines will be discussed for high-speed multimegawatt machines. The differences between the risk profiles for the PM and wound-field machines will be highlighted with a particular emphasis on the risk mitigation via tests for the PM machine.

Hybrid Excitation Synchronous Machines: Energy-Efficient Solution for Vehicles Propulsion

In this paper, the suitability of a class of electric machines for vehicle traction applications is discussed. These machines, which are known as hybrid excitation synchronous machines, combine permanent-magnet (PM) excitation with wound field excitation. The goal behind the principle of hybrid excitation is to combine the advantages of PM excited machines and wound field synchronous machines. It is shown that these machines have good flux weakening capability compared with PM machines, and that they constitute an energy-efficient solution for vehicle propulsion.

Speed Control of a Single-Frame Cascade Induction Motor with Slip-Power Pump Back

This paper describes an analytical and experimental study of a self-cascade single-frame brushless induction motor, using a rectifier- inverter to control speed by slip-power pump back to the line. Steady- state analyses of asynchronous and synchronous performance and test results of a special machine wound for the study are presented. The effect of machine parameters, windings, and construction is discussed. The performance and rating of the brushless cascade machine are found to be equivalent to the slip-ring induction motor or wound-field synchronous machine built into the same frame.