Soft-switching Inverter-fed Single-phase Collector Motor Drive Academic research paper on "Electrical engineering, electronic engineering, information engineering"

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Energy Procedía 50 (2014) 744 - 750

The International Conference on Technologies and Materials for Renewable Energy, Environment

and Sustainability, TMREES14

Soft-switching inverter-fed single-phase collector motor drive

Dimitar Spirova, Milko Dochevb*

a University of Food Technology, 26 Maritsa Blvd, Plovdiv 4000, Bulgaria b Technical University, 31 S.Saev Str, Lovech 5500, Bulgaria

Abstract

This paper deals with the performance analysis of a hand power tool (HPT). The HPT is being driven by a single-phase collector motor drive fed by a PWM voltage source soft-switching inverter. A mathematical model of an electro-mechanic system of a HPT has been worked out. The dynamic model of an electric motor consists of a system of non-linear differential equations that include the resistance and dynamic inductance of an armature and field winding and spinning E.M.F. The proposed drive system is modeled and its performance is simulated in Matlab/Simulink. The simulation results show that a smaller switching loss and higher conversion efficiency are obtained by the proposed soft-switching inverter. The performance of the drive is improved by using voltage regulator when compared with direct connection to the voltage source. © 2014 ElsevierLtd. Thisis anopenaccessarticleunder the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/3.0/).

Selection and peer-review under responsibility of the Euro-Mediterranean Institute for Sustainable Development (EUMISD) Keywords: Single-phase serial collector motor, power tool, H-bridge MOSFET soft-switching inverter;

1. Introduction

Single-phase collector machines are being used mainly in household electric appliances and power tools. Dynamic regimes within single-phase collector machines are of big importance, because these motors are subject to frequent starts, stops and reverses, big overloading and speed changes that significantly reflect on the isolation thermal life and the machine lagers and decrease their potential.

The linear dynamic models do not adequately show the behavior of single-phase collector machines at these working regimes. The development of non-linear mathematical models of these machines, that more fully reflect

* Corresponding author. Tel.: ++359 32/ 603791; fax: ++359 32/ 644 102. E-mail address: dimitar_spirov@abv.bg

1876-6102 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Selection and peer-review under responsibility of the Euro-Mediterranean Institute for Sustainable Development (EUMISD) doi:10.1016/j.egypro.2014.06.092

their real behavior, is an object of a high consideration of the specialists in electro-mechanical systems and automatic control of electric motors [1, 2, 3, 4].

It is known that regular converters used in the classical topology do not use appropriate commutation techniques, resulting in higher losses and higher electromagnetically interference [5]. In order to improve the commutation techniques and minimize its effects, two group's techniques can be used: active and passive [5, 6]. The active technique uses controlled switches to achieve soft commutation, whereas the passive technique does not use controlled devices. The active technique uses pulse width modulation (PWM) since it does not require complex control circuits.

The object of this work is to develop and simulated in Matlab/Simulink a single-phase collector motor drive fed by a PWM voltage source soft-switching inverter used for HPT. It is necessary to investigate a performance of proposed drive system for the dynamic and steady-state modes.

2. Mathematical models

The mathematical models have been developed under the following assumptions [1, 2, 3]:

- not to be given are the effects, connected to the collector and brushes commutation except from the losses in the commuting sections of the transformer E.M.F.;

- to be neglected as too small are inductivity variations of the windings that are connected with the motor spinning and are a result from the wire openings;

- the active rotor resistance are considered as constant;

Electro-mechanical energy conversion in the single-phase collector motor can be shown using the equations for the instant values of the quantities [4]. The system is written as following:

pi = Ai + Bu

pD. - (M -Mc)/ J^

(1) (2)

where:

u = [u ej ; i = [i is f

RsLdfs Ls Ls

(Le x ; B = Le Le

Rs (-La + Lf J Ldsf Ldsf

Le l_ Le Le

Le - Ls (La + Lf )" LdsfLdfs ; La ~ Lda + Lal ; Lf ~ Ldf + Lfl ; Ls ~ Lds + L

RaS, Rf, Rs - active resistances of armature winding, field winding, including the resistance of the brushes contact and the winding, that corresponds with the steel losses;

Lad, Lfd, Lsd, Lfsd, Lsfd - dynamic inductances of the windings;

Laa, Lfa, Lsa - static inductances of the windings;

M=^s(im)i - electromagnetic torque;

e=^gQ - spinning E.M.F.;

^s - air intermediate space linkage flux;

Q - angular speed of the rotor.

A mathematical model of a single-phase collector motor is going to be used which renders account to the non-linearity of an electromagnetic character. It allows for the influence of the saturation of the armature reaction linkage

flux, the field winding linkage flux and the air intermediate space linkage flux on the relevant parameters and characteristics of the single-phase collector motor at dynamic and steady-state regimes to be read [3]. The approximating dependencies for defining the parameters are given in Appendix A.

Single-phase full. bridge rectifier |

H-bridge inverter

CA+ " Da+2 1B+ _

La Ça 7 Da =

Sa+Sa-Sb+Sb

PWM PID

Generator Controller

Fig. 1. Voltage control scheme

-4 < 1

1 0 -1

4 0 -4

0,194399

0.19439

0.19439

0.19439

0.19439

0.19439

0.19439

t t„

0,19441

0.19441

0.19441

0.19441

0.19441

0.19441

_l t, s

0.19441

Fig. 2. Timing diagram

Usually the small power variable speed drives are powered from single phase AC mains through a diode bridge rectifier with smoothening DC capacitor and a voltage source inverter. The diode bridge rectifies the AC input voltage and the LC filter smoothes out the resulting voltage to make it an almost pure DC waveform. The armature winding of the single-phase collector motor (SPCM) is fed by a H-bridge inverter connected to a rectifier [7]. The reference value of the magnitude and phase of voltage applied to the armature winding are computed by the reference voltage block. By varying the auxiliary winding voltage magnitude, the torque ripples are alleviated at all operating points. The voltage control loop uses a proportional-integral-derivative (PID) controller [7].

The proposed circuit is shown in Fig. 1. This topology is similar to the classic converter, plus an auxiliary switch, a capacitor, and an auxiliary inductor. Capacitor C is responsible for the storage of the diode reverse recovery energy and for clamping the switches voltage. Inductor L is responsible for the control of the di/dt during the diode reverse recovery time. Scheme contains H-bridge inverter whose power switches are connected in parallel with additional resonant circuits. "Soft switching" is accomplished by the application of a suitable switching circuit for the formation of the switching signals of the power switches on the basis of the two-phase sine wave PWM signal, and the measured voltages on the power switches. A individual transistors control schemes are introduced. The control scheme fed a voltage to the gate of the corresponding transistor if the input of the individual scheme has a control signal and drain-source voltage of the transistor is practically zero [5, 6].

The proposed control scheme and the principle of operation of the scheme of Fig. 1 clarify a timing diagram of Fig. 2. At the moment t1 clogs transistor TA- after filing a signal to clog it. CA- capacitor is charged in LA in the range t1 ^ t2, as the applied voltage on CA- increased from 0 to UCmax = UDC. At the same time the capacitor CA+ was diluted to 0. The capacitor CA+ zero voltage is an indication of applying the control signal to the switch in which it will be unclog at zero voltage. At time t2 is unclogs reverse diode of the transistor TA+, which conducts until t3. At the moment t3 the current in LA changes direction and unclogs switch TA+. Thus the impulse to unblock the switch TA+ be filed later with the interval t1 ^ t2 after completion of the transition process to the exclusion of the transistor TA-.

3. Received results

Simulation is done on a single-phase collector motor fed by a PWM inverter developed in Matlab/Simulink. The figure 3 shows the Simulink diagram of the developed model. The basic circuit of the proposed scheme consists of a single-phase collector electric motor for HPT type BUR2-160E having ratings as 182W, 230V, 50 Hz which is connected to drive power tool BUR2-160E. The technical data of the electric motor are given in Appendix A.

(^t) us

A + e-e-nflflTl-B-j-^-B

/ C1 =p T

A . I .

Single-phase full- brdge rectifier

Soft switching scheme

Pulses Uref

'«-□ftn

■-nnnr>-

PWM Generator

PID Controller

H-brdge MOSFET inverter

is Uab —► —► 1 1

Me -►

Single-phase Scope collector motor

Fig. 3. Simulink diagram of the developed model

The single-phase collector motor drive is fed by a two-phase PWM voltage source soft-switching inverter. The modulation technique used for the generation of three phase balanced output from the inverter is the sinusoidal pulse width modulation technique. Voltage source pulse width modulated inverter is made up of four MOSFET switches in a bridge form (universal bridge) and fed by a dc voltage source of 350 V. Two-phase output is taken from of two arms of bridge circuit designated as 'A' and 'B', which is connected to the two phases 'A, B', on the stator side of single-phase collector motor.

System voltage control can be used as a soft start and to adjust the rotational speed of the machine. Simulation research is carried out when setting the voltage UAB ref from 0 to 0.1 s voltage increases from 0 to UN, is operating at

a nominal voltage of 0.1 to 3 s, and incrementally reducing the voltage to 0.5 UN. Fig. 4 shows the reference voltage rms value.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Fig. 4. Dependence Uab_ref=f(t)

With the use of the simulation models the dependencies of the work characteristics of the examined motor and the mechanism are found out in a function of time. Parts of the received results are being shown in the respective figures.

0.4 0.35 0.3 0.25

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Fig. 5. Dependences Qr=f(t) (a) and M=f(t) (b)

Management of inverter drives attached proposed control algorithm for "soft switching" voltage of the keys. Fig. 6 shows the shapes of the current, voltage and power losses in the switches of the test circuit. For comparison are shown in scheme losses without damper (Fig. 7).

From fig. 6 and fig. 7 is seen that the current through transistor TA+ begins to flow in the reset voltage on it. This led to a significant reduction in switching losses - in the case of pulses presented in the figure of 14.725 W when dealing with "hard switching" to 0.182 W when using "soft switching", ie 14.543 W reduce the emitted power. Amplitude value of current through the transistor TA+ at work "hard switching" is 3.959 A, when using "soft switching" is 3.080 A, ie with 0.879 reducing the amplitude value.

ab ref

S2 „, s

0.19439

0.19439

0.19441

t, s 0.19441

Fig. 6. Dependences uSA+, iSA+, pSA+ =f(t) with "soft switching" control scheme

Fig. 7. Dependences uSA+, isa+, Psa+ =f(t) with "hard switching" control scheme

4. Conclusion

This paper deals with the performance analysis of a HPT. The HPT is being driven by a single-phase collector motor drive fed by a PWM voltage source soft switching inverter. A mathematical model of an electro-mechanic

system of a HPT has been worked out. The dynamic model of an electric motor consists of a system of non-linear differential equations that include the resistance and dynamic inductance of an armature and field winding and spinning E.M.F. The proposed drive system is modeled and its performance is simulated in Matlab/Simulink. Simulation results show that the proposed scheme for the "soft switching" is obtained a significant reduction of the power losses in the power switches and the reduction of the amplitude values of the current through the transistors as compared with the scheme of "hard switching". The performance of the drive is improved by using voltage regulator when compared with direct connection to the voltage source.

Appendix A.

Technical data and parameters of a single-phase collector electric motor for HPT type BUR2-160E: Pn=182W; UaN=230V; IN=1,88A; Ubrush=2,5V f=50Hz; qN=33%; cosyN=0,93; nN=27081min'1; Jm=0,03.10~3kgm2;

RaZ=3,2Q; Rf=ll,2Q; Lsfi=Lfsi=Lsi=Lfc;; Laa=4,5.10'3H; Lfa=3.l0'3H; Lsa=Lfa Approximating correlations for defining of parameters:

Lai(i)=Wa(aibi/(bi+\i\)2+Ci); Lfi(i)=wjü2b2/(b2+\i\)2; Ws(iJ=Waa3iJ(b3+\im\); Rs(I)=a4+b4ec44;

wa=264; w=376; al=0,984.l0-4; bl=-0,7l43; c1=0,4321.10-4; a2=6,9764.l0-4; b2=0,6723; a3=4,9257.l0-4; b3=0,5329; a4=56,259; b4=604,l2; c4=-l,709.

References

[1] Spirov, D., P. Yordanov, M. Dochev. Power tools energy characteristics at dynamic and steady-state regimes. 9th INTERNATIONAL CONFERENCE RaDMI 2009, Vrnjacka Banja, Serbia, 2009, pp. 1233-1238.

[2] Yordanov, P., D. Spirov, M. Dochev. Power tools performance characteristics at dynamic and steady-state regimes. 9th INTERNATIONAL CONFERENCE RaDMI 2009, Vrnjacka Banja, Serbia, 2009, pp. 1258-1263.

[3] Bojilov, G., E. Ratz, M. Mihov, A. Ivanov. A simulation model of single-phase collector motor in taking to account of non-linear magnetizing curve of magnetic core. Annals of Technical University - Varna, 2004, pp. 354-359. (in Bulgarian)

[4] Dochev, M., G. Bojilov. Diagnostic computing model of a single-phase commutator motor for power tools "ELMA 99", Varna, 1999, pp. 106-109.

[5] Bankov, N., Al. Vuchev. Study modes of transistor resonant DC / DC converter. - Engineering Sciences, № 4, 2009, pp. 5-18. (in Bulgarian)

[6] Spirov D., Al. Vuchev, N. Bankov. Investigations of zero-voltage transition soft-switching inverter for an induction motor drive. Conference "Food Science, Engineering and Technology 2013", Plovdiv, pp. 197-200. (in Bulgarian)

[7] Spirov D., M. Dochev. Inverter-fed single-phase collector motor drive. RaDMI 2013, Kopaonik, Serbia, vol. 2, 2013, pp. 960-965.