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Abstract: Most three-phase, squirrel-cage, induction motors (SCIMs) are oversized. In the European Union (EU), the average load factor of SCIMs is slightly lower than 60%. In fact, in some industrial sectors, a large part of SCIMs operates with a load factor as low as 25%. Therefore, since the motor load factor is an average of its load over the operating cycle, it can be said that a large quantity of IMs operates with a load under 60%. In oversized IMs, if the actual load cycle is known, it is possible to properly redesign the original stator winding in order to match the peak efficiency with the maximum or dominant load, by means of a magnetizing flux reduction, ultimately leading to the motor power decrease (i.e., downsizing). Moreover, since the original motor active material quantity is maintained, the iron and copper losses and the magnetic saturation level will be reduced, improving the motor efficiency and power factor. In some cases, it is possible to convert an oversized standard motor into a well-sized high-efficiency motor, particularly if best practice is applied during motor repair/rewinding. Even considering the typical 1% efficiency drop due to poor-quality motor repair/rewinding, the motor efficiency gain after downsizing can still be significant. The motor lifetime can also be extended, which is an environmentally advantageous aspect. In this paper, a short review on optimized redesign of oversized SCIM stator windings is presented. Additionally, a large-scale rewinding-based motor downsizing strategy is proposed and the associated savings potential in the EU is estimated. [Copyright &y& Elsevier]

Examines the discrepancy between two testing standards for motor efficiency and establishes an approximate method to allow comparison between motors tested with the standards. Information on the Institute of Electrical and Electronic Engineers 112-B and the International Electrotechnical Commission 34-2 test standards; Main differences between the two testing standards; Efficiency data analysis.

• Study of a tubular linear actuator with a hybrid core (permanent magnet and ferromagnetic core) to increase force density. • Sensorless position detection using the variation of the coil current ripple with the variation of the core position. • Actuator prototype composed by a coil fed by a buck DC-DC converter. • Positioning control strategy experimentally tested for constant position and constant load force. In this paper, a study of a tubular linear actuator with a hybrid core is presented. Through a finite-element analysis software and force measurements, it is shown that, by using a hybrid core combining a permanent magnet and a ferromagnetic material, a higher force density can be achieved in relation of that achieved by using a ferromagnetic core alone. Also, by keeping the ferromagnetic part, the sensorless detection of the core position is possible. A simple position control strategy is proposed, using the inductance variation to indirectly detect the position of the core, in which the duty cycle of the PWM voltage is changed to compensate variations of position or load force. In order to experimentally test the linear motor with hybrid core and the proposed control strategy, a prototype and a control circuit were built. The experimental results clearly demonstrate the advantages and applicability of the hybrid core in linear actuators. [ABSTRACT FROM AUTHOR]

This study proposes an induction motor drive system based on the LC filter integrated quasi‐Z source indirect matrix converter (QZS‐IMC). The proposed drive system shows the following features: (i) variable voltage control of inductor motor is achieved by the rectifier stage and variable frequency control is achieved by the inverter stage; (ii) automatic low voltage ride through ability enhances capability of the proposed drive against grid voltage sag; (iii) wide voltage gain range ensures the drive system with high performance in wide speed range; (iv) there is no additional input filter. The voltage control implementation in the rectifier stage is proposed to benefit low voltage stress and low converter loss. The control method combines motor vector control, minimum shoot‐through duty cycle and maximum modulation indexes. As a result, the input power supply voltage and dc‐link voltage are maximally utilised and the power loss is reduced. Simulation and experimental results verify the proposed QZS‐IMC motor drive system. [ABSTRACT FROM AUTHOR]

Summary: The existing model of LC filter integrated quasi‐Z source indirect matrix converter (QZS‐IMC) was derived using the DC circuit modeling method, which is mainly effective in DC circuit. As an ac circuit, the existing voltage boost ratio model of LC filter integrated QZS‐IMC exhibits a big error from the real boost ratio. Moreover, current amplitude and phase angle of QZS network were not considered in the existing model. This paper proposes a new comprehensive model of LC filter integrated QZS‐IMC taking into account the circuit's ac characteristics. The new model shows that voltage boost ratio is strongly related to QZS network inductance, capacitance, and frequency of input power supply. It can be concluded from the new model that the boost ratio is higher than 1/(1 − 2D), which is the boost ratio of existing model. Moreover, the new model shows that power factor affects voltage gain of QZS‐IMC system. The new model is compared with the existing model, circuit simulation, and experimental test. The results verify the new model and analysis. [ABSTRACT FROM AUTHOR]