Induction motors are widely used in industrial processes. The malfunction of a motor may not only lead to high repair costs, but also cause immense financial losses due to unexpected process downtime. Since thermal overload is one of the major root causes of stator winding insulation failure, an accurate and reliable monitoring of the stator winding temperature is crucial to increase the mean time to catastrophic motor breakdown, and to reduce the extraordinary financial losses due to unexpected process downtime. To provide a reliable thermal protection for induction motors fed by motor control devices, a dc signal-injection method is proposed for in-service induction motors fed by soft-starter and variable-frequency drives. The stator winding temperature can be monitored based on the estimated stator winding resistance using the dc model of induction motors. In addition, a cooling capability monitoring technique is proposed to monitor the cooling capability of induction motors and to warn the user for proactive inspection and maintenance in the case of cooling capability deterioration. The proposed cooling capability monitoring technique, combined with the proposed stator winding temperature monitoring technique, can provide a complete thermal protection for in-service induction motors fed by motor control devices. Aside from online thermal protection during a motor's normal operation, the thermal protection of de-energized motors is also essential to prolong a motor's lifetime. Moisture condensation is one of the major causes to motor degradation especially in high-humidity environments. To prevent moisture condensation, a non-intrusive motor heating technique is proposed by injecting currents into the motor stator winding using soft-starters. A motor's temperature can be kept above the ambient temperature due to the heat dissipation, so that the moisture condensation can be avoided. To sum up, active stator winding temperature estimation techniques for induction motors under both operating and de-energization conditions are proposed in this dissertation for both thermal protection and optimizing the operation of a motor system. The importance of these proposed techniques lies in their non-intrusive nature: only the existing hardware in a motor control device is required for implementation; a motor's normal operation is not interrupted.

Multi-level inverters play a significant role in high power drive systems for induction motors. Interest in multi-level inverters started with the three-level, neutral point clamped (NPC) inverter. Now there are many topologies for higher number of levels such as the, flying capacitor and cascaded H-bridge etc. The advantage of multi-level inverters is the reduced voltage stress on the switching devices, lower dv/dt and lower harmonic content. The voltage space vector structure in a multi-level inverter has a hexagonal periphery similar to that in a two-level inverter. In the over-modulation region in multi-level inverters, there is the presence of lower order harmonics such as 5th and 7th in the output voltage, and this can be avoided by using a voltage space vector scheme with more than six polygonal voltage space vectors such as 12, 18, 24 etc. These polygonal voltage space vectors can be generated by using multi-level inverter topologies, by cascading two-level inverter structures with asymmetric DC-links. This thesis deals with the development of 12-sided and 18-sided polygonal voltage space vector schemes for induction motor drives. With the 12-sided polygonal structure, all the 5th and 7th harmonic orders and 6n±1, n=1, 3, 5.. are absent throughout the modulation range, and in the 18-sided voltage space vector scheme, 5th, 7th, 11th and 13th harmonics are absent throughout the modulation range. With the absence of the low order frequencies in the proposed polygonal space vector structures, high frequency PWM schemes are not needed for voltage control. This is an advantage over conventional schemes. Also, due to the absence of lower order harmonics throughout the modulation range, special compensated synchronous reference frame PI controllers are not needed in current controlled vector control schemes in over-modulation. In this thesis a method is proposed for generating 12-sided polygonal voltage space vectors for an induction motor fed from one side. A cascaded combination of three two-level inverters is used with asymmetrical DC-links. A simple space vector PWM scheme based only on the sampled reference phase amplitudes are used for the inverter output voltage control. The reference space vector is sampled at different sampling rates depending on the frequency of operation. The number of samples in a sector is chosen to keep the overall switching frequency around 1kHz, in order to minimize switching losses. The voltage space vectors that make up the two sides of the sector in which the reference vector lies, are time averaged using volt-sec balance, to result in the reference vector. In the proposed 12-sided PWM scheme all the harmonics of the order 6n±1, n=1, 3, 5... are eliminated from the phase voltage, throughout the modulation range. In multi-level inverters steps are taken to eliminate common-mode voltage. Common-mode voltage is defined as one third of the sum of the three pole voltages of the inverter for a three phase system. Bearings are found to fail prematurely in drives with fast rising voltage pulses and high frequency switching. The alternating common-mode voltage generated by the PWM inverter contributes to capacitive couplings from stator body to rotor body. This generates motor shaft voltages causing bearing currents to flow from rotor to stator body and then to the ground. There can be a flashover between the bearing races. Also a phenomenon termed EDM (Electro-discharge machining) effect occurs and may damage the bearings. Common-mode voltage has to be eliminated in order to overcome these effects. In multi-level inverters redundancy of space vector locations is used to eliminate common-mode voltages. In the present thesis a 12-sided polygonal voltage space vector based inverter with an open-end winding induction motor is proposed, in which the common-mode voltage variation at the poles of the inverter is eliminated. In this scheme, there is a three-level inverter on each side of the open-end winding of the induction motor. The three-level inverter is made by cascading two, two-level inverters with unequal DC-link voltages. Appropriate space vectors are selected from opposite sides such that the sum of the pole voltages on each side is a constant. Also during the PWM operation when the zero vector is applied, identical voltage levels are used on both sides of the open-end windings, in order to make the phase voltages zero, while the common-mode voltage is kept constant. This way, common-mode voltage variations are eliminated throughout the modulation range by appropriately selecting the voltage vectors from opposite ends. In this method all the harmonics of 6n±1, n=1, 3, 5.. and triplen orders are eliminated. In the 12-sided polygonal voltage space vector methods, the 11th and 13th harmonics though attenuated are not eliminated. In the 18-sided polygonal voltage space vector method the 11th and 13th harmonics are eliminated along with the 5th and 7th harmonics. This scheme consists of an open-end winding induction motor fed from one side by a two-level inverter and the other side by a three-level inverter comprising of two cascaded two-level inverters. Asymmetric DC-links of a particular ratio are present. The 12-sided and 18-sided polygonal voltage space vector methods have been first simulated using SIMULINK and then verified experimentally on a 1.5kW induction motor drive. In the simulation as well as the experimental setup the starting point is the generation of the three reference voltages v, vB and vC . A method for determining the sector in which the reference vector lies by comparing the values of the scaled sampled instantaneous reference voltages is proposed. For the reference vector lying in a sector between the two active vectors, the first vector is to be kept on for T1 duration and the second vector for T2 duration. These timing durations can be found from the derived formula, using the sampled instantaneous values of the reference voltages and the sector information. From the pulse widths and the sector number, the voltage level at which a phase in the inverter has to be maintained is uniquely determined from look-up tables. Thus, once the pole voltages are determined the phase voltages can be easily determined for simulation studies. By using a suitable induction motor model in the simulation, the effect of the PWM scheme on the motor current can be easily obtained. The simulation studies are experimentally verified on a 1.5kW open-end winding induction motor drive. A V/f control scheme is used for the study of the drive scheme for different speeds of operation. A DSP (TMS320LF2407A) is used for generating the PWM signals for variable speed operation. The 12-sided polygonal voltage space vector scheme with the motor fed from a single side has a simple power bus structure and it is also observed that the pole voltage is clamped to zero for 30% of the time duration of one cycle of operation. This will increase the overall efficiency. The proposed scheme eliminates all harmonics of the order 6n±1, n=1, 3, 5…for the complete modulation range. The 12-sided polygonal voltage space vector scheme with common-mode elimination requires the open-end winding configuration of the induction motor. Two asymmetrical DC-links are required which are common to both sides. The leg of the high voltage inverter is seen to be switched only for 50% duration in a cycle of operation. This will also reduce switching losses considerably. The proposed scheme not only eliminates all harmonics of the order 6n±1, n=1, 3, 5…for the complete modulation range, but also maintains the common-mode voltage on both sides constant. The common-mode voltage variation is eliminated. This eliminates bearing currents and shaft voltages which can damage the motor bearings. In the 18-sided polygonal voltage space vector based inverter, the 11th and 13th harmonics are eliminated along with the 5th and 7th. Here also an open-end winding induction motor is used, with a two-level inverter on one side and a three-level inverter on the other side. A pole of the two-level inverter is at clamped to zero voltage for 50% of the time and a pole of the three-level inverter is clamped to zero for 30% of the time for one cycle of operation. The 18-sided polygonal voltage space vectors show the highest maximum peak fundamental voltage in the 18-step mode of 0.663Vdc compared to 0.658Vdc in the 12-step mode of the 12-sided polygonal voltage space vector scheme and 0.637Vdc in the six-step mode of a two-level inverter or conventional multi-level inverter (where Vdc is the radius of the space vector polygon). Though the schemes proposed are verified on a low power laboratory prototype, the principle and the control algorithm development are general in nature and can be easily extended to induction motor drives for high power applications.

<p>This thesis deals with the integral motor of tomorrow, and particularly with a variable speed, sensorless permanent magnet synchronous motor with an integrated converter. The rated power is 15 kW at 1500 r/min. The outer dimensions are approximately the same as for the equivalent standard induction motor.</p><p>Control strategies for pumps and fans, i.e. suitable loads for variable speed motors, are briefly described. The huge energy savings that can be made by reducing the speed instead of throttling/choking the flow are pointed out. Compared to installing an induction motor with a separate converter, a PM integral motor will probably pay-off in less than a year.</p><p>A <i>totally analytical</i> expression for calculating the airgap flux density of permanent magnet motors with buried magnets is derived. The analytical expression includes axial leakage, and iron saturation of the most narrow part of the magnetic circuit of the machine.</p><p>A computer program for optimization of PM motors with buried magnets has been developed. It was used to design the manufactured prototype PM integral motor, and the parameters are investigated with analytical and/or FEM calculations. The optimization program is also used to suggest nearoptimum pole numbers for desired powers (4-37 kW) and speeds (750- 3000 r/min) of inverter-fed PM motors. Results show that compact buried PM motors should have relatively large airgaps and high NdFeB-magnet masses to improve the efficiency. Ferrite magnets are unsuitable.</p><p>Measurements on the manufactured PM motor, the novel concept of stator integrated filter coils, and the complete PM integral motor are presented. Special attention was given to temperature and overall efficiency measurements.</p><p>The rotor cage losses were investigated by time-stepping FEM. Four short circuit fault conditions were also examined in order to evaluate the risks of demagnetization of the buried magnets. </p>

In this dissertation, the generalized averaging method models for inverters, reactive power control methods for photovoltaic inverters, and a noise immunity improvement for hybrid position observers for brushless dc motor drives are studied. Models of inverters and other converters based on averaging have been widely used in numerous simulation applications. Generalized averaging can be applied to model both average and switching behavior of converters while retaining the faster run times associated with average-value models. Herein, generalized average models for single- and three-phase pulse width modulation inverters are proposed. The modulation signal for the proposed model could be either a sinusoidal waveform without high order harmonics or a sinusoidal waveform with third-harmonic injection. And this generalized average models also can apply for modeling three-phase pulse width modulation inverters with varying modulation signal frequency in the reference frame. These models are based on a quasi-Fourier series representation of the switching functions that includes fundamental and switching frequency components as well as sideband components of the switching frequency. The proposed models are demonstrated both in simulation and experimentally and are found to accurately portray both the fundamental and the switching behavior of the inverter. In particular, the use of sideband components allows accurate representation of the variation in switching ripple magnitude that occurs in the steady state. The generalized average models are found to have simulation run times that are significantly faster than those associated with detailed models. Therefore, the proposed generalized average models are suitable for simulation applications in which both accuracy (including the switching behavior) and fast run times are required (e.g., long simulation times, systems with multiple converters, and repeated simulations). Variations in the output power of intermittent renewable sources can cause significant fluctuations of distribution system voltage magnitudes. Reactive power control methods that employ the reactive power capability of photovoltaic three-phase inverters to mitigate these fluctuations are proposed. These control methods cause the three-phase inverters to substitute reactive output power for real output power when fluctuations in the solar power are experienced, allowing the fluctuations to be controlled. Performance metrics for assessing the ability of these controllers to perform this mitigation are defined. The controllers are examined using the IEEE 123-bus feeder distribution system, and it is found that the controllers can effectively mitigate voltage magnitude fluctuations and that the appropriate choice of controller depends on the performance metrics of interest. Finally, a noise immunity improvement for hybrid position observers for brushless dc motor drives is proposed. A finite state machine is used to detect Hall-effect sensor transitions to determine if these transitions are true transitions or the result of momentary glitches. This filter causes a delay in the detection of the Hall-effect sensors that is compensated in the proposed observer. The proposed observer is compared in simulations with the original hybrid position observer under both non-noisy and noisy conditions for both constant and variable speed operation, and it has good performance even under high noise and variable speed conditions.

The main theme of this thesis is an analysis, desing and construction of a planetary gearbox used for a drive of a vertical lathe table. The theoretical part of the thesis describes fundamental features and terms of planetary gearboxes and torque motors. In the next part of my work I design loose functioning of toothing. The calculation part of my work is processed in accordance with technical standards. The practical part of my work deals with a description of the project and the implementation of the device. The drawing documentation is processed with Cad system and it includes general assembly drawing and drawings of the three important components.

No description available.

This work demonstrates the capability of a power electronic based power hardware-inthe- loop (PHIL) platform to emulate electric machines for the purpose of a motor drive testbench with a particular focus on induction machine emulation. PHIL presents advantages over full-hardware testing of motor drives as the PHIL platform can save space and cost that comes from the physical construction of multiple electric machine test configurations. This thesis presents real-time models that were developed for the purpose of PHIL emulation. Additionally, real-time modeling considerations are presented as well as the modeling considerations that stem from implementing the model in a PHIL testbench. Next, the design and implementation of the PHIL testbench is detailed. This thesis describes the design of the interface inductor between the motor drive and the emulation platform. Additionally, practical implementation challenges such as common mode and ground loop noise are discussed and solutions are presented. Finally, experimental validation of the modeling and emulation of the induction machine is presented and the performance of the machine emulation testbench is discussed. / Master of Science / According to the International Energy Agency (IEA), electric power usage is increasing across all sectors, and particularly in the transportation sector [1]. This increase is apparent in one's daily life through the increase of electric vehicles on the road. Power electronics convert electricity in one form to electricity in another form. This conversion of power is playing an increasingly important role in society because examples of this conversion include converting the dc voltage of a battery to ac voltage in an electric car or the conversion of the ac power grid to dc to power a laptop. Additionally, even within an electric car, power converters transform the battery's electric power from a higher dc voltage into lower voltage dc power to supply the entertainment system and into ac power to drive the car's motor. The electrification of the transportation sector is leading to an increase in the amount of electric energy that is being consumed and processed through power electronics. As was illustrated in the previous examples of electric cars, the application of power electronics is very wide and thus requires different testbenches for the many different applications. While some industries are used to power electronics and testing converters, transportation electrification is increasing the number of companies and industries that are using power electronics and electric machines. As industry is shifting towards these new technologies, it is a prime opportunity to change the way that high power testing is done for electric machines and power converters. Traditional testing methods are potentially dangerous and lack the flexibility that is required to test a wide variety of machines and drives. Power hardware-in-the-loop (PHIL) testing presents a safe and adaptable solution to high power testing of electric machines. Traditionally, electric machines were primarily used in heavy industry such as milling, processing, and pumping applications. These applications, and other applications such as an electric motor in a car or plane are called motor drive systems. Regardless of the particular application of the motor drive system, there are generally three parts: a dc source, an inverter, and the electric machine. In most applications, other than cars which have a dc battery, the dc source is a power electronic converter called a rectifier which converts ac electricity from the grid to dc for the motor drive. Next, the motor drive converts the dc electricity from the first stage to a controlled ac output to drive the electric machine. Finally, the electric machine itself is the final piece of the electrical system and converts the electrical energy to mechanical energy which can drive a fan, belt, or axle. The fact that this motor drive system can be generalized and applied to a wide range of applications makes its study particularly interesting. PHIL simplifies testing of these motor drive systems by allowing the inverter to connect directly to a machine emulator which is able to replicate a variety of loads. Furthermore, this work demonstrates the capability of PHIL to emulate both the induction machine load as well as the dc source by considering several rectifier topologies without any significant adjustments from the machine emulation platform. This thesis demonstrates the capabilities of the EGSTON Power Electronics GmbH COMPISO System Unit to emulate motor drive systems to allow for safer, more flexible motor drive system testing. The main goal of this thesis is to demonstrate an accurate PHIL emulation of a induction machine and to provide validation of the emulation results through comparison with an induction machine.

No description available.

Hysteresis current control has been widely used in power electronics with the advantages of fast dynamic response under parameter, line and load variation and ensured stability. However, a main disadvantage of hysteresis current control is the uncertain and varying switching frequency which makes it difficult to form an average-value model. The changing switching frequency and unspecified switching duty cycle make conventional average-value models based on PWM control difficult to apply directly to converters that are controlled by hysteresis current control. In this work, a new method for average-value modeling of hysteresis current control in boost converters, three-phase inverters, and brushless dc motor drives is proposed. It incorporates a slew-rate limitation on the inductor current that occurs naturally in the circuit during large system transients. This new method is compared with existing methods in terms of simulation run time and rms error. The performance is evaluated based on a variety of scenarios, and the simulation results are compared with the results of detailed models. The simulation results show that the proposed model represents the detailed model well and is faster and more accurate than existing methods. The slew-rate limitation model of hysteresis current control accurately captures the salient detail of converter performance while maintaining the computational efficiency of average-value models. Validations in hardware are also presented.

To develop more competitive solutions, one of the trends in the development of drive systems for electric and hybrid electric vehicles (EVs/HEVs) is to integrate the power electronic converter and the electric motor. This thesis aims to investigate the performance and the operation of modular converters in integrated motor drive systems for EVs/HEVs. In the first part, the concept of integrated modular motor drive systems for EVs/HEVs is introduced. Three suitable modular converter topologies, namely, the stacked polyphase bridges (SPB) converter, the parallel-connected polyphase bridges (PPB) converter and the modular high frequency (MHF) converter, are evaluated and compared with conventional electric drives in terms of power losses, energy storage requirements, and semiconductor costs. In the second part of the thesis, the harmonic content of the dc-link current of the SPB converter is analyzed. By adopting an interleaving modulation the size of the dc-link capacitor can be reduced without increasing the switching frequency, which is beneficial for achieving a compact integrated system. This method allows for around 80% reduction of the dc-link capacitance for vehicle drives, resulting in a significant size reduction of the power converter and improved integration. Finally, a communication-based distributed control system for the SPB converter is presented. The communication delay arising from the serial communication is inevitable, thus a timing analysis is also presented. It has been found that stability is maintained even when the baud rate of the SPI communication is lower than 1 Mbps, indicating that other communication protocols with lower bandwidths can also be adopted for this topology. The analytical investigations provided in this thesis are validated by experiments on a four-submodule laboratory prototype. Experimental results verify the correctness of the theoretical analysis, as well as the dynamic performance of the distributed control system. / <p>QC 20161121</p>