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УДК 621.314.57
АНАЛИЗ ПАРАМЕТРОВ И ХАРАКТЕРИСТИК ВЫХОДНЫХ ФИЛЬТРОВ du/dt ЭЛЕКТРОМАГНИТНОЙ СОВМЕСТИМОСТИ ТРЕХФАЗНЫХ ПРЕОБРАЗОВАТЕЛЕЙ ЧАСТОТЫ НА ЛИНЕЙНОЕ НАПРЯЖЕНИЕ 380 В
Индылова Н. В., Пустоветов М. Ю.
Донской государственный технический университет, г. Ростов-на-Дону, Российская Федерация
[email protected] [email protected]
UDC 621.314.57
ANALYSIS OF PARAMETERS AND CHARACTERISTICS OF OUTPUT FILTERS du/dt ELECTROMAGNETIC COMPATIBILITY OF THREE PHASE FREQUENCY CONVERTERS ON 380 V PHASE-TO-PHASE VOLTAGE
Indylova N. V,. Pustovetov M.Y.
Don State Technical University , Rostov-on-Don, Russian Feederation
[email protected] [email protected]
As a result of the analysis of the parameters of the filters produced by Danfoss, analytical expressions are obtained for determining their inductance and capacitance depending on the load power of the frequency converter. Numerical values of the characteristics important for the synthesis of filters are also determined. Keywords: frequency-controlled electric drive, EMC filter, frequency converter, inductance, capacitance.
В результате анализа параметров фильтров, выпускаемых фирмой Danfoss, получены аналитические выражения для определения их индуктивности и емкости в зависимости от мощности нагрузки преобразователя частоты. Определены численные значения важных для синтеза фильтров характеристик. Ключевые слова: частотно-регулируемый электропривод, фильтр электромагнитной совместимости, преобразователь частоты, индуктивность, емкость.
Introduction. The problems of electromagnetic compatibility are closely related to the reliability and safety of a frequency-controlled electric drive [1 - 5]. In particular, the requirements of [6] limiting the permissible amplitude of the pulse of the phase-to-phase voltage supplied from the frequency converter (FC) to the motor terminals, from the rise time of the pulse are established. Ordinary, a limitation is set on the rate of increase of the voltage coming from FC to motor, du / dt = 500 V / p,s. It also states that the voltage and voltage rise limits can be achieved by connecting inductor or a low-pass filter to the output of FC (a filter that effectively passes the frequency spectrum of the signal below the cutoff frequency and suppresses the frequency of the signal above this frequency), connected in series, and shunt capacitor.
One of the types of low-pass filters, practically used for the stated purpose, is a filter du / dt. The variant of its scheme is shown in Fig. 1. The filter consists of three phase reactors L and three capacitors C, each connected either between two phases (triangle circuit) or between phase and neutral point (wye circuit). Resistors R are added to adjust the high-frequency components of the voltage spectrum [1, 2]. However, resistors R that are parallel to L inductances may be absent. When using the filter du / dt, the voltage form on the motor terminals remains impulsive [1, 5].
It is known that for filters du / dt, the inductance values of the reactors and capacitors are selected in such a way that frequency suppression is provided above the switching frequency of the power keys of
the inverter (the cutoff frequency is much higher than the switching frequency of the transistors of the inverter (the carrier frequency of the pulse-width modulation)). The inductance is in the range from a few tens to several hundreds of ^H, the capacitance of capacitors is within a few tens of nF. Filters du / dt can be used at lower switching frequencies of the transistor than the nominal frequency indicated for the filter. On the contrary, the switching frequencies above the rated frequency should be avoided, since work on them can lead to overheating of the filter [7]. However, this information is not enough to synthesize the filter.
Fig. 1. A variant of the du/dt filter circuit
Formulation of the problem. The purpose of this article is to analyze known technical solutions in the field of du / dt filters and to derive on its basis the patterns for the synthesis of filter parameters for their design, modeling, and so on.
When developing a new device, it is always welcome to familiarize with existing analogues. As such an analogue, the basis for the analytical study, we will use the published data on Danfoss filters for a line voltage of 380 V [7]. Table. 1 contains the parameters and characteristics of the filters according to [7] (the active power of the three-phase load of the frequency converter P, the effective value of the load phase current I, the inductance of the filter phase L, the filter phase capacitance C, the maximum filter losses Apmax, the minimum switching frequency of the inverter fs ), and the results of calculations based
on them (cutoff frequency fc, voltage drop on the inductance at a frequency of 50 Hz as a percentage of
the nominal phase voltage of 220 V AuL%, frequency multiplicity fc / fs , the fraction of losses in the
filter from the nominal load power Ap%, the equivalent active resistance of the filter phase Reqv ). We
assume that the capacitance values in [7] are indicated for the case of their connection in the wye scheme. Theory. Calculations in Table. 1 are satisfied by the following formulas:
fc =( 2WTC )-1; AuL% = 2k-f • L I-100%/V , where f = 50 Hz; V = 220 V - effective value of phase voltage;
Ap% = Apmax -100%/P ; K = Apmax / 3/ 12.
Fig. 2 and Fig. 3 shows the equations of trend lines representing mathematical expressions relating the values of the du / dt filter parameters to the power of the three-phase load fed from the FC, and also the value of the accuracy of the approximation by the trend line given in Table. 1 parameter values (point-
markers) is the coefficient of determination, informing about the extent to which this trend explains the location of the initial points.
Table 1
Parameters and characteristics of filters
Initial data [3] Calculation results
P I L C ^Pmax fs fe f / f awl% AP% Reqv
kW А ^H nF W kHz kHz p. u. % % mOhm
11 24 150 10 4 130 32 0,51
15 32 150 10 4 130 32 0,69
18,5 37,5 150 10 4 130 32 0,80
22 44 150 10 37 4 130 32 0,94 0,17 6,37
30 61 110 13,6 3 130 43 0,96
37 73 110 13,6 3 130 43 1,15
45 90 110 13,6 130 3 130 43 1,41 0,29 5,35
55 106 95 15 145 3 133 44 1,44 0,26 4,30
75 147 111 15 3 123 41 2,33
90 177 111 15 205 3 123 41 2,81 0,23 2,18
110 212 50 20 3 159 53 1,51
132 260 50 20 3 159 53 1,86
160 315 50 20 315 3 159 53 2,25 0,20 1,06
200 395 30 43 3 140 47 1,69
250 480 30 43 398 3 140 47 2,06 0,16 0,58
315 600 17 66 2 150 75 1,46
355 658 17 66 550 2 150 75 1,60 0,15 0,42
400 745 13 99 2 140 70 1,38
450 800 13 99 2 140 70 1,49
500 880 13 99 850 2 140 70 1,63 0,17 0,37
1000
X
i 01 100 ^ ■V"
и с (б
<J
■с с
^ ■м 10
ÜL У = -42,04ln(x) + 266,03
R2 = 0,9372
1
0 100 200 300 400 500
Load power (kW)
Fig. 2. Approximation of the du/dt filter inductance per phase by analytic function
120
100
80
S. 60
л
и ^
£ 40
y = 0,0002x2 + 0,1123x + 7,0909 R2 = 0,966
20 0
0
• •
100 200 300 400
Load power (kW)
500
Fig. 3. Approximation of the du/dt filter capacitance per phase by analytic function
Conclusion. As a result of analyzing the parameters of the filters produced by Danfoss, analytical expressions for determining L and C depending on the power of the FC load are obtained, and the
values of the characteristics that are important for the synthesis of filters are calculated: fp/ fK, AuL% u .
Bibliography
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