RU2042210C1 - Apparatus for monitoring modes of equipment operation - Google Patents

Abstract

FIELD: measuring technique. SUBSTANCE: apparatus has input resistors 1,2,3, the voltage transformer 4, the current transformer 9, switches 11, 12, the connecting resistor 13, limiting resistors 14,15, operational amplifiers 8, 16, 20, the low frequency filter 17, registering units 18, 23, the pulse width modulator 10, the integrating capacitor 19, single-shot multivibrator 21, the comparator 22. The apparatus provides monitoring of an active power, being consumed by it, or a registration of electric energy, being consumed by it. EFFECT: enhanced accuracy of operation of the apparatus, enlarged using range of the apparatus. 1 cl, 1 dwg

Description

 The device can be used in systems for measuring the active power and energy consumed by equipment, in shaft systems of telemechanics and in other telemechanical systems for transmitting information about the active power of equipment, in ACS by power facilities and is designed to work in symmetric three-phase circuits for measuring the active power of a three-phase circuit by active power of one phase.

A device is known for monitoring the operating modes of equipment by measuring the active power of a single-phase alternating current, consisting of a multiplying unit on quadrators, input intermediate voltage and current transformers [1]
The disadvantage of this device is the low accuracy due to the difficulty of obtaining an accurate quadratic dependence on the squaring elements.

A device for monitoring the operating modes of equipment by measuring power in symmetric three-phase circuits with an isolated neutral by connecting a measuring body to line voltage and phase current [2]
The disadvantage of such devices is their low accuracy and manufacturability, which is explained by the need to eliminate the initial phase shift of 30 ^about between the phase current and line voltage. The use of RC elements for phase correction leads to a large phase error when the network frequency changes and requires an individual adjustment of the phase of each device, which is not technologically advanced.

Closest to the invention in technical essence and the achieved result is a device for monitoring the operating modes of the equipment of a symmetric three-phase circuit, which contains a time-pulse multiplication unit, consisting of the first, second and third operational amplifiers, a key on a field-effect transistor connected directly to the phase of the controlled equipment, and pulse-width modulator, and the first operational amplifier is connected to phases B and C of the three-phase circuit through resistors, thereby achieving nenie initial phase shift between voltage and current, key management is provided by a pulse width modulator, the relative difference between the length of output pulses of voltage which is proportional to the current of phase A, the output signal is taken from the output of the third operational amplifier through a low-pass filter and applied to recorder [3]
The disadvantage of this device is the low accuracy due to the influence of the resistance of the public key on the accuracy of the measurement of active power. The disadvantage of this device is also a narrow scope, since it has only one output recorder for connecting an analog device or relay organ and does not have a frequency output, which does not allow directly using these devices to control the power consumption of equipment by measuring the consumed electricity. The narrow scope of this device is also determined by the fact that the keys and the pulse-width modulator have direct galvanic connection with the power circuit, which excludes the possibility of using the device in high-voltage networks (660, 1000 V and above).

 The aim of the invention is to increase the accuracy of the device and expand its scope, since when monitoring the operating modes of the equipment by active power, increasing the reliability and reliability of the control is increased by increasing the accuracy, and it is also possible to control the mode not only by active power, but also by energy consumption, which reduces energy consumption and conserves energy.

 A device for monitoring the operating modes of the equipment shown in the drawing.

 The device contains input resistors 1, 2 and 3 included in the star and connected to a three-phase network voltage system, voltage transformer 4 from the primary winding 5, the first 6 and second 7 secondary windings, the first operational amplifier 8, current transformer 9, pulse-width modulator 10, switches 11 and 12, a connecting resistor 13, limiting resistors 14 and 15, a second operational amplifier 16, a low-pass filter 17, a first recorder 18, an integrating capacitor 19, a third operational amplifier 20, a single-shot 21, a comparator 22 (with sensitivity), the second registrar 23.

 A device for monitoring the operating modes of the equipment is as follows.

(1) где R₁ сопротивление резистора 1. По закону полного тока для трансформатора 4 напряжения имеет место следующее равенство:
i₅ ω₅ i₇ ω₇ + i₆ ω₆ Hl, (2) где ω₅ ω₆ ω₇ числа витков 5, 6, 7; Н напряженность магнитного поля в сердечнике трансформатора 4; l средняя длина магнитной силовой линии сердечника трансформатора 4.The current i _a , proportional to the voltage of phase A, is supplied through the keys 11 and 12 to the inverting inputs of the amplifiers 16 and 20. Since the first secondary winding 6 of the transformer 4 is connected to the input of the first operational amplifier 8, the voltage on it U _{6 is the} same as on the primary winding 5 U _a and the second secondary winding 7 U ₇ are equal to zero, provided that the amplifier 8 is perfect. Therefore, the current i ₅ in the winding 5 is equal to i ₅

(1) where R _{1 is the} resistance of resistor 1. According to the law of the total current for voltage transformer 4, the following equality holds:
i ₅ ω ₅ i ₇ ω ₇ + i ₆ ω ₆ Hl, (2) where ω ₅ ω ₆ ω _{7 are the} number of turns 5, 6, 7; H magnetic field in the core of the transformer 4; l the average length of the magnetic line of force of the core of the transformer 4.

(3) где S_Fl сечение сердечника трансформатора 4.U ₆ = ω ₆ S _Fl

(3) where S _{Fl is the} cross section of the core of the transformer 4.

i₅

·

U_A= KU_A
(4)
Следовательно, ток в обмотке 7, подводимый через ключи 11 и 12 к инвертирующим входам операционных усилителей 16 и 20, пропорционален напряжению фазы А U_A и не зависит, что существенно, от величины сопротивления в цепи обмотки 7, т.е. от величины сопротивлений открытых ключей, включенных в цепи этой обмотки.Since U ₆ is equal to zero, the rate of change of induction in the core of transformer 4 is also equal to zero, therefore, the core of transformer 4 is not magnetized and H 0. Taking into account also that amplifier 8 is ideal, i ₆ 0 is taken into account. Considering this, from expressions (2) and (1) receive
i ₇ =

i ₅

·

U _A = KU _A
(4)
Therefore, the current in the winding 7, supplied through the keys 11 and 12 to the inverting inputs of the operational amplifiers 16 and 20, is proportional to the phase voltage A U _A and does not depend, which is important, on the resistance value in the winding circuit 7, i.e. on the value of the resistance of the public keys included in the circuit of this winding.

(5) где R₁₃, R₁₄ сопротивления резисторов 13, 14. Полагая R₁₃ R₁₄, получают
i_{19 ср} i₇

(6)
Широтно-импульсный модулятор 10 обеспечивает преобразование входного тока i_A согласно зависимости

K_ii_A (7)
Подставив выражения (4) и (7) в уравнение (6), получают
i_19cp K U_A ^. K_i i_A K ^.K_i U_A i_A K_c U_A i_A. (8)
Как видно из выражения (8) средний за время t₁ + t₂ ток на входе усилителя 20 равен произведению мгновенных значений напряжения и тока фазы А контролируемой сети, т.е. мгновенной мощности фазы А сети Р_А.Depending on the polarity of the pulse output voltage of the pulse-width modulator 10, the winding current 7 i _{7 is} directly connected when the transistor 11 is open, or the current i _{7 is} inverted by the amplifier 16 when the transistor 12 is open. The integrating amplifier 20 extracts the average for one cycle the work of a pulse-width modulator current value i ₇ . Considering that the duration of the positive pulse of the pulse-width modulator when the key is open 11, t ₁ , and the duration of the negative pulse when the key is open 12, t ₂ , determine the average value for the input current cycle of the modulator (time t ₁ + t ₂ ) amplifier 20 L _19cp , assuming that the time t ₁ + t _{2 is} much less than the period of change of the network voltage T _s and during this time the network voltage U _A , and therefore the current i ₇ remain unchanged:
i _{19 avg} =

(5) where R ₁₃ , R _{14 of the} resistance of the resistors 13, 14. Assuming R ₁₃ R ₁₄ , get
i _{19 wed} i ₇

(6)
Pulse-width modulator 10 provides the conversion of the input current i _A according to the dependence

K _i i _A (7)
Substituting expressions (4) and (7) into equation (6), we obtain
i _19cp KU ^_A. K _{i i A} ^K. K _i U _A i _A K _c U _A i _A. (8)
As can be seen from expression (8), the average current at time t ₁ + t ₂ at the input of amplifier 20 is equal to the product of instantaneous values of voltage and current of phase A of the controlled network, i.e. instantaneous phase power network A R _A.

K_cU_Amsinωt·I_Amsin(ωt-φ)dt K_cU_AI_Acosφ K_cP_A
(9) где U_A и I_A эффективные значения напряжения и тока сети; Р_А активная мощность фазы А сети.If we make the integration and averaging i _19cp the period T _s, is obtained by sinusoidally changing current _{i A = I Am sin (ω} t -φ) and the voltage U _A U _Am sin ω t following expression for the average over the period T _c of the current at the input integrator:
I _{19 avg} =

K _c U _Am sinωt I _Am sin (ωt-φ) dt K _c U _A I _A cosφ K _c P _A
(9) where U _A and I _{A are the} effective values of the voltage and current of the network; P _{A is the} active power of phase A of the network.

равнялось нулю, т.е. импульс калиброванной длительности тока

должен уравновесить среднее значение тока I_19cp за период Т_к. Следовательно,
I_{19 ср}·T_k=

(10) где R₁₅ сопротивление резистора 15.The one-shot 21 generates a pulse of a calibrated volt-second area I ₀ U ₀ const with a voltage polarity U ₀ opposite to the current I _19cp , which is connected through a resistor 15 to the inverting input of the amplifier 20 and resets the capacitor 19 to its initial state. The switching frequency of the comparator 22 with the dead zone, and therefore the one-shot 21 is set so that the average current at the input of the amplifier 20 for the switching period T _to

equal to zero, i.e. calibrated current pulse

should balance the average current value I _19cp for a period of T _to . Hence,
I _{19 cf.T k} =

(10) where R _{15 is the} resistance of resistor 15.

K_f и учитывая, что Т_к

а также выражение (9), получают
K_c P_A K_f ^.f. (11)
Из выражения (11) следует
f

P_A= K_p·P_A где К_р коэффициент пропорциональности.Marking

K _f and given that T _to

as well as expression (9), get
K _c P _A K _f ^. f. (eleven)
From the expression (11) it follows
f

P _A = K _p · P _A where K _{p is the} coefficient of proportionality.

 Therefore, the switching frequency f of the comparator 22 and the one-shot 21 is proportional to the power of phase A.

 The second recorder 23 registers the frequency f, i.e. active power consumed by the equipment, thereby controlling the mode of operation of the equipment by active power. If the recorder 23 counts the pulses coming from the output of the comparator 22 with a frequency f for a certain time, then in this case, the operating mode of the equipment for the consumption of active electricity is monitored for the recorded time interval. Thus, the device monitors the operating mode of the equipment, as it provides control of the active power consumed by it or the registration of consumed electricity.

 The device has a wider scope, since due to the presence of a voltage transformer it can be used in high voltage networks, while the use of a prototype that does not have galvanic isolation of the circuit from the power circuit in high voltage circuits is unacceptable.

 The device has a higher accuracy of monitoring the operating mode of the equipment, since the voltage transformer together with the first operational amplifier eliminates the influence of changes in the resistance of the keys on the accuracy of the circuit.

Claims (1)

 DEVICE FOR CONTROL OF EQUIPMENT OPERATING MODES, containing the first, second and third input resistors connected to the corresponding power phases, the first operational amplifier, the first key, the output of which is connected to the inverting input of the second operational amplifier and through the fourth connecting resistor to the input of the low-pass filter, which connected to the output of the second operational amplifier, the output of the low-pass filter is connected to the first recorder, the third operational amplifier, pulse-width modulator, fifth sixth limiting resistors, non-inverting inputs of the first, second and third operational amplifiers are connected to a common power bus, characterized in that a voltage transformer, a current transformer, a comparator, a one-shot, a second switch and a second recorder are inserted into the device, the primary winding of the voltage transformer is connected to the first and second conclusions respectively to the first input resistor and the common connection point of the second and third input resistors, the first secondary winding of the voltage transformer connected between the common power bus and the inverting input of the first operational amplifier, the output of which through the second secondary winding is connected to the inputs of the first and second keys, the control inputs of which are connected to the outputs of the pulse-width modulator, the input of which is connected to the current transformer, the output of the second key through the fifth limiting a resistor is connected to the input of the low-pass filter and is connected to the inverting input of the third operational amplifier, in parallel with which an integrating capacitor is connected, the output of the rd operational amplifier is connected to the input of the comparator, whose output is connected to a second input of the registrar and monoflop, whose output is the sixth through limiting resistor connected to the inverting input of the third operational amplifier.