Fractional slot, PMSM motors with a properly designed electromagnetic circuit allow for obtaining high power density factors (more than 4 kW per 1 kg of total motor weight). The selection of the number of magnetic poles to the specific dimensions and operating conditions of the motor, as well as the number of slots for the selected number of magnetic poles is the subject of the analysis in this article. This issue is extremely important because it affects the mass of the motor, the value of shaft torque, shaft power and the value of rotor losses. The aim of the work is to select solutions with the highest values of power density factor and, at the same time, the lowest values of rotor losses. The object of the study is a fractional slot PMSM motor with an external solid rotor core with surface permanent magnets (SPM). Motor weight is approximately 10 kg, outer diameter is 200 mm and a maximum power is 50 kW at 4800 r/min. The article analyzes the selection of magnetic poles in the range from 2p = 12 to 2p = 24 and various slot-pole combinations for individual magnetic poles. The target function of the objective was achieved and the calculations results were verified on the physical model. The best solutions were 20-pole, 30-slots (highest efficiency and lowest rotor loss) and 24-pole, 27 slots (highest power density).
The paper presents an experimental device that was created in order to obtain the real values of the forces acting in the vertical direction on the lock-off element, the so-called brake body, the 2nd design option. The lock of this design is used in the automated parking garage, designed by KOMA-Industry, s.r.o, to lock the parked vehicles on pallets in the units of the rack parking system. The forces acting in the vertical direction on the body of the fixation lock when pushing the brake pulley into the circular recess in the brake ramp are theoretically calculated for two design variants of the brake ramp used in practice, i.e. "without" and "with" a rounded (filleted) circular recess segment in the brake ramp. The experimentally determined forces acting in the vertical direction on the brake body were determined for two types of compression coil springs with a rectangular cross section of the spring wire.
This article deals with the development of capacitive voltage divider for high voltage measurements and presents a method of analysis and optimization of its parameters. This divider is a part of a combined voltage and current sensor for measurements in high voltage power networks. The sensor allows continuous monitoring of the network distribution status and performs a quick diagnosis and location of possible network failures. Deployment of these devices will support semi-autonomous control of power networks and it can be considered as a step from traditional power grids toward smart grids. This is a worldwide trend connected with increasing number of renewable energy sources and plug-in electric vehicles as described in. In this way, it contributes to the reliability of the distribution network. Together with automated control techniques and fault location methods, it enables its self-healing capability. The following characteristics required for the sensor include: current measurement error up to 2 %, voltage measurement error up to 0.5 %, and power measurement error up to 5 %. At the same time, it is necessary that the sensor is cost-effective - relatively cheap. There were selected capacitors made in series production for the capacitive divider designing. The capacitive voltage divider was tested in terms of time and temperature stability; the results are described in the paper. Then, the method of mathematical correction of a temperature dependence of the capacitive voltage divider was suggested and tested.
Given that most sensorless methods use the "flux linkage" algorithm for their control, this paper deals with possibilities to improve this sensorless method. When using the sensorless "flux linkage" method it is necessary to know not only the values of phase voltages and currents, but also the correct value of the phase resistance. During the operation of the switched reluctance motor, the value of the phase resistance is significantly changing due to the temperature dependence. Such resistance error causes an inaccurate estimation of the flux linkage. For this reason, it was desirable to implement a sensorless control algorithm for estimating phase resistance. In this paper, the experimental results of the implemented algorithm for estimating the phase resistance under the sensorless operation of a switched reluctance motor are presented. The practical implementation of control of the switched reluctance motor is carried out using a control system with a 16-bit digital signal processor.
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