Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: napędy o zmiennej prędkości

Sortuj według:

Ogranicz wyniki do:

A new sensorless speed control structure for PMSM using reference model

100%

Urbanski K.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2017

tom Vol. 65, nr 4

489--496

In the paper a new sensorless control structure for the PMSM drive is presented. Such a structure is especially recommended for speed in the range of single revolutions per second (excluding standstill). The method uses a back EMF observer for position estimation. However, there is no need to estimate the speed. This is a big advantage because of possible irregularity of estimated back EMF in this speed range, which makes the calculation of speed difficult or impossible. The proposed structure is similar to the model following control, but the reference model attempts to track the motor operating point. The main idea is to utilize as a reference a model of the whole drive, including speed and current controllers and motor model. Such a model produces reference voltage for the real inverter. However, an extra unit – called rotator – is needed to provide precise control of direct axis current, which is sensitive to the improper position of the voltage vector. The rotator acts as a kind of compensator for error of position estimation.

Regulacja zmiennoobrotowa pomp sieciowych w aspekcie blokady minimalnego ciśnienia kotłów wodnych

100%

Misiewicz A.

2008

tom Vol. 13, spec. iss. 2/2

40--45

An article presents the influence of the minimum vapour pressure blockade of the water boilers over the pumps working area, specially for pumps with variable speed drives. The city heating system needs the defined value of out-come pressure. Simultanously the boilers needs the minimum blockade pressure on the outlet, against the water vapour. Usually the value of this pressure is constant, uninfluenced from the working temperature. When the value of vapour pressure (on the blockade) is higher than the out-come system pressure, the working area of variable speed driving pumps is decreasing, and the effect of using the variable drives is lower. The using the self-changed vapour pressure blockade increase the working area of the pumps. This article presents the results of using the variable pressure blockade in the water boilers and connected with it energetistic effects, as a pumping efficiency increase.

Electric shock hazard in circuits with variable-speed drives

100%

Czapp S. , Guzinski J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2018

tom Vol. 66, nr 3

361--372

The conventional approach to electrical safety under fault condition in typical power systems considers earth fault currents of sinusoidal waveform and frequency of 50‒60 Hz. However, in circuits with variable-speed drives, there is earth fault current flow with harmonics, and these harmonics influence the threshold of ventricular fibrillation. The paper presents earth fault current waveforms in circuits with variable-speed drives without inverter output (motor) filter and with one of the two types of inverter output filters being used. The details of both filters are presented, and the effect of harmonics of earth fault current on ventricular fibrillation is evaluated. Furthermore, the effect of harmonics, which occurs in circuit of variable-speed drive, on the tripping current of residual current devices is presented. Residual current devices may be utilized to ensure protection against direct and indirect contact, but limitations in their proper operation, due to harmonics, may exist. Operational characteristics of a proposed residual current device dedicated to circuits with earth fault current containing harmonics, as in the variable-speed circuits, are presented.