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1

Electric shock hazard in circuits with variable-speed drives

Czapp S., Guzinski J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2018

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Vol. 66, nr 3

361--372

EN

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.

2

A new sensorless speed control structure for PMSM using reference model

Urbanski K.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 4

489--496

EN

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.

3

Procesorowy układ sterowania silnika BLDC z bocznikowaniem części uzwojenia do napędu pojazdu elektrycznego

Fręchowicz A.

Maszyny Elektryczne : zeszyty problemowe

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2013

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Nr 2(99)

281--286

PL

Jednym z możliwych rozwiązań napędu samochodu elektrycznego jest zastosowanie bezszczotkowego silnika prądu stałego. W napędach trakcyjnych wymagany jest szeroki zakres regulacji prędkości obrotowej, przy czym przy większych prędkościach moment rozwijany przez silnik może być mniejszy. Dlatego w napędach tego typu chętnie stosuje się silniki pracujące w dwóch strefach regulacji prędkości: pierwszą strefę nazywamy strefą stałego momentu, a drugą – strefą stałej mocy. W bezszczotkowych silnikach prądu stałego, pracę w drugiej strefie można osiągnąć przez elektroniczne bocznikowanie części uzwojenia. Poniżej przedstawiony będzie układ regulacji prędkości obrotowej takiego napędu. Układ sterowania został zrealizowany w postaci rozproszonej sieci mikrokontrolerów CAN. Główny węzeł sieci CAN wykonano na procesorze sygnałowym TMS320LF2407A firmy Texas Instruments, którego bogate wyposażenie wewnętrzne umożliwia równoczesne sterowanie dwoma zespołami kluczy tranzystorowych. W omawianym rozwiązaniu, jedna część układów wewnętrznych mikrokontrolera steruje tranzystorami falownika (praca w I strefie), a druga część – tranzystorami zwierającymi części uzwojeń (praca w II strefie). Omówiona będzie budowa układu, działanie oprogramowania i wnioski wynikające z prac uruchomieniowych. Przedstawiony zostanie schemat blokowy układów sterowania. Cechą charakterystyczną napędu samochodu jest praca w szerokim zakresie regulacji prędkości obrotowej. Z tego faktu wypływają pewne wymagania odnośnie harmonogramu wykonywania poszczególnych procedur. Również te zagadnienia zostaną przedstawione w opracowaniu.

EN

One of possible drives for electric car is brushless dc motor. In traction drives we usually require wide range of speed control, and at greater speeds the motor torque may be less. That is why motors operating in two speed control zones are regularly applied; the first zone is called constant torque zone and the second is constant power zone. In dc brushless motor the second control zone may be achieved by shunting (electronically)part of the winding. The speed control circuit for this type of drive is presented. The control circuit Has been designed as a distributed CAN microcontroller network. The main node of CAN network has been butli with Texas Instruments signal processor TMS320LF2407A. The developed architecture of this procesor makes it possible to control two sets of electronic switches at the same time. In the discussed system, one set of microcontroller internal circuits controls the inverter switches (first control zone), and the other set controls transistors shunting parts of the windings (second control zone). The structure of the circuit, software performance and some implementation remarks are described together with block diagram of control circuits. The characteristic feature of this car drive is wide range of speed control. Some requirements as to run Schedule of different procedures are due to this fact. These issues are also presented in the paper.

4

Regulacja zmiennoobrotowa pomp sieciowych w aspekcie blokady minimalnego ciśnienia kotłów wodnych

Misiewicz A.

Systems : journal of transdisciplinary systems science

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2008

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Vol. 13, spec. iss. 2/2

40--45

EN

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.