Uwe Schaefer

Detailed Design of a High Speed Switched Reluctance Starter/Generator for More/All Electric Aircraft

Abstract The basic concepts and advantages of more/all electric aircraft (M/AEA) are briefly addressed. The combined starter/generator (CS/G) system is introduced as a key technology to enable M/AEA. Some important performance requirements for CS/G system are obtained. Based on these requirements, a high speed switched reluctance machine (SRM) is designed to operate as a starter/generator. The entire design process is mainly divided into two stages: electromagnetic design and thermal design. In electromagnetic design stage, the electromagnetic structure and dimensions of the machine and the number of phase winding turns per pole are obtained; the topology and main technical details of the converter are briefly introduced as well. In thermal design stage, a liquid-cooling system is designed based on the thermal analysis of the machine. In the end, the performances of the designed SRM are basically verified by simulation. To get high performances, the exciting angles are optimized in two different operating modes respectively, and the optimized performances in the motoring mode are given as well.

Power conditioning of a 132 MW wind farm

A possible reason for a low power quality at the output of a 132 MW wind farm is investigated. A resonant circuit formed by the wind farm components is found to be responsible for a high level of the dominating 7th current harmonic. Various compensation strategies are proposed and analyzed.

Malfunction of a dead-time compensation in PWM-converters leading to a high DC current offset

A new source for the DC current offset in the PWM inverter-fed loads is found. A significant irregularity in dead time voltage compensation due to a very small offset in phase current measurement is the cause for it. In the phase currents and voltages, high DC offsets appear at low current magnitudes, which lead to a first torque harmonic in the drive. Recommendations how to avoid or compensate this effect are given in the paper.

Low cost integrated motor-controller drive for an electrical active suspension system

This paper presents an electrical drive designed for an electrical active suspension system with motor, pump wheel and power electronics integrated in the same housing, sharing the same cooling method. The proposed drive is designed for the new 48V automotive standard for auxiliary drives having a maximum load of 2.5kW. The necessary mechanical and electrical requirements for the complete drive are documented. Design guidelines are presented for the integrated power electronics and motor drive and verified through experimental results. Thermal simulations are conducted to support the thermal design of the system.

Thermal analysis of a 30kW Switched Reluctance Starter/Generator system used in aircraft

The application background and operating principle of the Switched Reluctance Starter/Generator (SR S/G) system are briefly introduced. The structure and technical parameters of an undergoing 30kW Switched Reluctance Machine (SRM) and its converter are described. Based on these works, the thermal analysis of the SRM and its converter are presented in detail. The transient lumped-parameter thermal models are built to predict the thermal characteristics of SRM and converter. To keep the maximum temperature rise of the system in a safe range, the required thermal properties of the cooling system, such as maximum thermal resistance, are obtained. These properties are very important for the design of the cooling system, the selection of the heat sink and the optimization of the whole system.

Study on the communication between FPGA and observer using Controller Area Network and UART

This paper first studies the two protocols: Controller Area Network (CAN) and Universal Asynchronous Receiver and Transmitter (UART). In particular, it focuses on their effective data transmission rates and ratios. Next it lists the common Microcontrollers (MCU) to estimate their highest baud rates. Furthermore, this paper describes how to design a non data loss communication system working at the highest transmission rate. Finally, this paper demonstrates a complete measurement system using an Altera FPGA, an Atmel CAN MCU and an NI USB CAN interface and verifies the measurement results before coming to a conclusion.

Torque ripple in PWM-VSI-fed drives due to parasitic effects in the inverter control

Smooth torque production is one of the most important quality criteria for PWM-VSI-fed drives operation. In an ideal case merely additional torque harmonics of the switching frequency and of its multiples occur compared to sinusoidal power supply operation of a drive. At switching frequencies in kHz-range they are absorbed by the inertia of the machine and do not deteriorate the drive performance. Although additional low order torque harmonics may occur due to parasitic effects during the PWM operation. Low order torque harmonics are particularly undesired, because they may cross the mechanical resonance frequency of a drive train. New low order torque harmonic sources are described in the paper and compensation methods are proposed for them.

Torque maximization of a high-speed switched reluctance starter in acceleration test

This paper presents a torque maximization control strategy of a high speed switched reluctance machine and describes an indirect torque measurement based on acceleration. The SRM operates as a Starter/Generator for a more electric aircraft application with the requirement of an average torque of at least 15 Nm up to a speed of 27,000 rpm, which must be available for 15 s according to [4]. Maximum torque acceleration is intended to be used to start up the turbine to idle speed. The acceleration method was used to validate the torque-speed characteristic in the described starting mode. Both in high acceleration and high speed systems, a direct torque measurement would be a big challenge because of the delay time of the torque sensor. Therefore, the torque was measured indirectly by analyzing the acceleration according to the speed rise. In order to achieve numerically stable results, an additional inertia was provided.

Resonance in the 132 MW Wind Farm With Long High Voltage Cable and its Compensation

Abstract The origin for the low power quality at the output of a 132 MW wind farm has been investigated. A resonant circuit formed by the wind farm components is found to be responsible for a high level of the 7th current harmonic. The structure of the investigated wind farm is similar to those of offshore wind farms with AC cable connection. The same resonance problem is expected to occur in offshore installations with long high voltage AC cables. Various compensation strategies are proposed and analyzed.

High first torque harmonic due to insufficient function of dead time compensation in PWM inverters

A new source for the DC current offset in the PWM inverter-fed loads is found. A significant irregularity in dead time voltage compensation due to a very small offset in phase current measurement is the cause for it. In the phase currents and voltages, high DC offsets appear at low current magnitudes, which lead to a first torque harmonic in the drive. Recommendations how to avoid this effect are given in the paper.