Arvind Kumar Tiwari

Experimental investigation on switching characteristics of IGBTs for traction application

In traction application, inverters need to have high reliability on account of wide variation in operating conditions, extreme ambient conditions, thermal cycling and varying DC link voltage. Hence it is important to have a good knowledge of switching characteristics of the devices used. The focus of this paper is to investigate and compare switching characteristics and losses of IGBT modules for traction application. Dependence of device transition times and switching energy losses on dc link voltage, device current and operating temperature is studied experimentally.

Implementation and control of a bidirectional high-gain transformer-less standalone inverter

This paper describes a bidirectional inverter topology for standalone applications. The topology, consisting of a Quadratic Boost Converter based Voltage Source Inverter (VSI), can achieve high conversion ratio both in inverter as well as rectifier operations without the use of a transformer. In addition, the same architecture can also be used to realize DC-DC conversion (both Step-Up and Step-Down). This improves the adaptability of the topology in renewable system realization, especially in rural areas, and makes it suitable to handle variable input sources. The bidirectional power transfer capability with high conversion ratio is demonstrated using a lab prototype. The controller design for the topology operating as a standalone inverter is described in a step-by-step manner and this has been implemented using TMS320F28335 DSP. The output voltage regulation capability, when the high-gain inverter is subjected to load-step changes as well as variable input, has been validated using experimental results.

Experimental study on the dependence of IGBT switching energy loss on DC link voltage

In traction applications, power electronic converters experience wide variation in DC link voltage during operation. The purpose of this paper is to study the variations in turn-on and turn-off switching energy losses in the IGBTs with the DC link voltage. The IGBT switching characteristics are measured at various operating conditions, and turn-on and turn-off switching energy losses are determined. The experimental data are used to deduce a simple mathematical relationship between the switching energy losses and the DC link voltage. The results are useful for precise evaluation of IGBT switching energy loss over a wide range of operating conditions.

Experimental study on switching characteristics of an inverter leg consisting of IGBTs of dissimilar makes

Usually the top and bottom IGBT devices in an inverter leg are of the same make (i.e. from same manufacturer). At low power level, these two devices even may be contained in the same module. However at high power levels the top and bottom devices are in separate modules. Sometimes, in the event of device failure, device of particular make may be replaced by one of another make, but of same ratings (on account of non-availability of the original make). This paper investigates the effect of such intermixing of two different makes of high power IGBTs in an inverter leg on the switching characteristics. The switching transitions between IGBT and diode of similar make and those of IGBT and diode of dissimilar make are compared experimentally at various DC link voltages and currents. The comparisons are made in terms of, IGBT peak turn-on di/dt, IGBT peak turn-off di/dt, peak diode reverse recovery current (Irr), peak IGBT voltage overshoot and switching energy losses.

Variation of IGBT switching energy loss with device current: An experimental investigation

Aim of this paper is to study the variations in turn-on and turn-off switching energy losses in the IGBTs with device current at different DC link voltages and junction temperatures. The IGBT switching characteristics are obtained experimentally at various operating conditions, and turn-on and turn-off switching energy losses are determined. The relationship between the switching energy losses and the device currents are presented in mathematical form, which are derived from experimental data. Finally, a comparison has been made between calculated switching energy loss from linearized loss model and the derived expression from actual measured loss.

Motor Protection Principles

This paper discusses the fundamentals of motor protection principles. Every motor is designed for a specific operating temperature depending upon its insulation. Once this limit is exceeded its life decreases drastically. Over heating condition may arise due to several factors like supply system disturbance, electrical unbalance conditions, faults, load variation and environment. It is essential to have a proper coordination between development of protection principles and the design of motors to understand the concept of motor heating and how thermal protection for motors can be used to prevent loss of motor life. In this paper an overview of existing protection methods for motors is reviewed with a special consideration of thermal protection of motors.

Experimental study on the influence of junction temperature on the relationship between IGBT switching energy loss and device current

Accurate determination of power losses in semiconductor devices is important for optimal design and reliable operation of a power converter. The switching loss is an important component of the total device loss in an insulated-gate bipolar transistor (IGBT) in a voltage source inverter. The objective here is to study experimentally the influence of junction temperature on the turn-on switching energy loss E-on and turn-off switching energy loss E-off. More specifically E-on and E-off are both related to device current I-c; the influence of junction temperature on the relationship between E-on and I-c and that between E-off and I-c is studied. As the operating environmental conditions and load conditions of power converter vary widely, a wide range of junction temperatures between -35 degrees C and + 125 degrees C is considered here. The experimental data enable precise determination of the switching loss in each device in a high-power converter at any practical operating condition. This leads to precise estimation of total device loss and optimal thermal design of the converter. This further helps off-line and/or on-line estimation of device junction temperatures required for study of thermal cycles and reliability.