RU2280948C2 - Generator for inputting current signal to three-phase mains - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: proposed generator that can be used in organizing communication channels in three-phase, 0.4 to 35 kV mains without equipping them with high-frequency wavetraps at the same time enhancing efficiency by 25% due to dispensing with circuit limiting resistors and also due to adequate choice of optimal OFF-state time of switch τ = 016To, where To is ON-time of switch, is characterized in that its force-disconnected thyristor can be replaced by transistor due to eliminating switch-actuated discharge capacitor in its circuit.

EFFECT: enhanced operating reliability of generator.

1 cl, 1 dwg

Description

The invention relates to the field of electrical engineering and can find application in organizing communication channels using three-phase electrical networks (0.4-35 kV), without processing them with high-frequency chokes. Achievable technical result - increased generator efficiency by 25%.

It is known “Device for transmitting signals over a three-phase power line” (AS SU No. 1107750 A, H 04 B 3/54, 1982). A disadvantage of the known device is the absence of a limiting resistance in the signal key circuit (key), which must limit the current through the key, when it is closed, if for some reason, for example during a thunderstorm, it was not turned off at the set time, the device will burn out before the fuses fail.

Also known is a generator with a passive-active method of inputting signal currents into a three-phase electric network, which is adopted as a prototype (GENERATOR). (K.I. Gutin, V.V. Nosov, S.A. Tsagareishvili. Electricity distribution networks as communication channels of information-control systems. - Devices and Control Systems, M., 1995, No. 11, p. 49) .

A generator of a passive-active type is also known, which is adopted as a prototype (S. A. Tsagareishvili, K. I. Gutin. Theoretical foundations of constructing a channel-forming device at tonal frequencies on electric networks (0.4-35) kV. - Science and Technology in industry, M., 2001, No. 2 (5), p. 56). The efficiency is increased due to the removal of the limiting resistor and discharge capacitors from the generator circuit. Instead of a thyristor with forced locking, a transistor can be used, which will increase the reliability of the generator.

A diagram of a generator that implements the claimed technical solution is shown in the drawing, where:

1. Transformer 10 / 0.4 kV (transformer).

2. 0.4 kV network (network).

3. The first inductor (coil 3).

4. The first capacitor (capacitor 4).

4.1. The prototype capacitor is shown in dotted lines.

5. The first diode bridge. Note: diodes 5 ₁ , 5 ₂ , 5 ₃ , 5 ₄ are shown in the circuit of diode bridge 5 (bridge 5) to describe the operation of the generator.

6. The prototype resistor is shown with a dotted line.

7. Signal key (key).

8. 8, 9, 10 - resistors, respectively, the first, second, third (resistors 8, 9, 10).

11. The second inductor (coil 11).

12. The second capacitor (capacitor 12).

13. The second diode bridge (bridge 13).

14. The third inductor (coil 14).

15. The third capacitor (capacitor 15).

16. The third diode bridge (bridge 16).

Due to the fact that the circuit of the generator that implements the claimed method consists of three identical elements formed by coils 3, 11, 14 - bridges 5, 13, 16 - capacitors 4, 12, 15 it is enough to consider the operation of one of them, which is formed, for example, by coil 3, bridge 5, capacitor 4, the operation of the other two elements will be identical.

In the PROTOTYPE GENERATOR between the points T ₁ and T ₂ (drawing), which are connected to the network according to the “Phase” - “Phase” circuit, a capacitor 4 _{1 is} turned _on , which is charged when the key is open. When the key is closed, this capacitor is discharged along the circuit: "plus" of the capacitor 4 ₁ , diode 5 ₁ , resistor 6 - key - diode 5 ₃ - "minus" of the capacitor 4 ₁ . In order to avoid current surges that will disable the key, a limiting resistor 6 is installed. There is no capacitor 4 _{1 in the} declared generator, therefore there is no limiting resistor 6. It should also be noted that a PROTOTYPE GENERATOR must be used as a key with a forced thyristor by closing, and in the APPLIED GENERATOR it is possible to use a transistor due to the absence of a capacitor 4 ₁ , which is discharged through the key.

WORK OF THE STATED GENERATOR.

Let the potential of Phase A be higher than the potential of Phase B, i.e. open diodes of the bridge 5 ₁ and 5 ₃ . In the drawing, they are darkened. A key opening pulse of duration τ came to the key information input. The key was opened and the current i (t) of the charge of coil 3 with electromagnetic energy W went through it.

where L is the inductance of the coil 3; 2I _m is the amplitude value of current i (t) at time t = τ, while the value of current i (t) is equal to:

- амплитуда питающего напряжения; R_L - активное сопротивление катушки 3;Where

- the amplitude of the supply voltage; R _L is the resistance of the coil 3;

where f ₀ is the switching frequency of the key; Q = 20 - quality factor of the coil 3.

The charge current of coil 3 flows through the circuit: low-voltage winding of the Phase A transformer - coil 3 - diode 5 ₁ - key - diode 5 ₃ - low-voltage winding of the Phase B transformer.

Due to the stored electromagnetic energy W in the coil 3 in the time interval τ≤t≤T ₀ with the switch open in the series oscillatory circuit formed by the low-voltage winding of the Phase A transformer - coil 3 - by the capacitor 4 - by the low-voltage winding of the Phase B transformer, they form a free oscillation current i ₀ (t) _AB (signal current)

the oscillatory circuit is tuned into resonance at a frequency f ₀

Expression (3) can be written

Thus, despite the fact that the switch is switched at a frequency f ₀ , two currents are introduced into the network phases at frequencies f ₁ and f ₂ i.e.

Due to the large value of the quality factor of coil 3, attenuation in the serial oscillatory circuit is neglected, we also neglect the inductances of the transformer windings and the active resistances of the transformer windings, bridge diodes, the key, due to their smallness compared to the inductances of the coils and the active resistances of the coils.

DETERMINATION OF THE VALUE OF CHARGE CURRENT 2I _m IN THE PROTOTYPE GENERATOR

Elements of the PROTOTYPE GENERATOR have the following meanings:

R _CR = 8 Ohms - the value of the resistor of the prototype 6 (drawing);

L _CR = 4,57 · 10 ^-3 GN - the magnitude of the inductance of the charging coil 3 of the prototype;

замкнутого положения ключа;

locked key position;

f ₀ = 833 Hz - thyristor switching frequency;

U _m = 536 V is the amplitude of the supply voltage. By analogy with (2)

we have

Where

R _Σ = R + R _{L, pr}

R = 8 Ohms - resistance of the resistor 6 (drawing);

активное сопротивление катушки 3;

active resistance of coil 3;

Q = 20 - quality factor of the coil 3;

We solve (6) taking into account (7)

DETERMINATION OF THE OPTIMAL VALUE OF THE CLOSED STATE OF THE KEY τ IN THE APPLICABLE GENERATOR.

From the resonance condition (4)

- амплитуда питающего напряжения; 2I_m - амплитуда тока биения колебаний в момент времени t=τ.Where

- the amplitude of the supply voltage; 2I _m is the amplitude of the beat current of the oscillations at time t = τ.

We transform (9) with respect to 2I _m

On the other hand, when the key is locked, by analogy with (2) for t = τ, we have

2I _m is the amplitude of the charge current of the electromagnetic energy of coil 3 at time t = τ;

R _L is the resistance of the coil 3;

L is the inductance of the coil 3,

Where

We take Q = 20 - the quality factor of the coil 3.

Further we show that the quantity

Provided that (13) is satisfied, we can approximately assume that

In view of (14), expression (11) takes the form

Equate (10) and (15)

Or

Or

We solve (16) with respect to τ

Where

In the PROTOTYPE GENERATOR, the time of the open state of the key is equal to

IN THE DECLARED GENERATOR

which is the OPTIMAL value, i.e. we have

The index "pr" stands for PROTOTYPE GENERATOR. It follows that the charge of coil 3 is carried out more intensively than in the PROTOTYPE GENERATOR by 1.57 times, while the amplitudes of the currents in both the prototype generator and the claimed generator will be the same and equal to 2I _m = 26 A according to (8) We determine the inductance of coil 3 taking into account (8) and (15), while the current in the APPLIED GENERATOR will be equal to the current in the PROTOTYPE GENERATOR

We determine the capacitance of the capacitor 4 taking into account (18)

а в ЗАЯВЛЕННОМ ГЕНЕРАТОРЕ

Thus, at the same currents in the PROTOTYPE GENERATOR and the APPLIED GENERATOR 2I _m = 26 A, the parameters L and C will be different, which is natural, because key closed time

and in the APPLIED GENERATOR

Determine the active resistance of coil 3 taking into account (18)

We calculate the value of the current amplitude 2I _m in the inventive generator by analogy with (8), taking into account (17), (18), (20)

Comparing the results in (8) and (21), we see that they are identical.

DETERMINE EFFICIENCY IN THE STATED GENERATOR AND IN THE PROTOTYPE GENERATOR.

It is known that the efficiency for all generators with energy storage in inductors depends on the value

For the PROTOTYPE GENERATOR, this value is

Where

For the ANNOUNCED GENERATOR, this value is equal to

Where

Thus, the quantity (25) satisfies the condition

With a value of (25) equal to 0.05, the error in formula (14) does not exceed 0.1% (I.N. Bronstein. A reference to mathematics. M.: Gostekhizdat, p. 119).

We determine the efficiency of the generators from the function graph

(M.S. Neumann. The course of radio transmitting devices. - M.: Soviet Radio, 1965, p. 408 Fig. 4.26).

For PROTOTYPE GENERATOR taking into account (23)

For the APPLIED GENERATOR taking into account (25)

Resistors 8, 9, 10 are installed to relieve overvoltages on the circuit elements that form the key, at the time of its switching and the absence of them in the PROTOTYPE GENERATOR is also one of its shortcomings. The value of these resistors is 500 kOhm.

FINDINGS

The efficiency of the APPLIED GENERATOR is increased by 25% compared to the PROTOTYPE GENERATOR, which follows from (28) and (29), by reducing the key open state time by 1.56 times, as well as removing resistor 6 from the PROTOTYPE GENERATOR, while the current magnitude in the PROTOTYPE GENERATOR and the APPLIED GENERATOR have equal values, i.e. equal to 2I _m = 26 A.

Thus, the goal set by the invention is achieved.

Where

W _CR - the maximum value of the stored electromagnetic energy in the first coil of the PROTOTYPE GENERATOR;

R _ave = 8 ohm - resistance of the resistor 6 prototype generator;

Q = 20 - the quality factor of the inductors in the PROTOTYPE GENERATOR and in the STATED GENERATOR;

- отрезок времени замкнутого состояния ключа в ГЕНЕРАТОРЕ ПРОТОТИПА;

- time interval of the closed state of the key in the PROTOTYPE GENERATOR;

_Etc. L - inductance of the first coil in the prototype generator;

- период частоты коммутации ключа;

- period of key switching frequency;

2I _m is the amplitude value of current i (t) in the STATED GENERATOR at τ = 0.16T ₀ ;

L ₁ and C ₁ - inductance and capacitance of the first coil and the first capacitor in the APPLIED GENERATOR

ω ₁ = 2πf ₁ ; ω ₂ = 2πf ₂ ; f ₁ = f ₀ -F; f ₂ = f ₀ + F;

L ₂ and C ₂ - inductance and capacitance of the second coil and the second capacitor in the APPLIED GENERATOR, while taking L = L ₁ = L ₂ ; C = C ₁ = C ₂ .

- активное сопротивление катушки 3 в ЗАЯВЛЕННОМ ГЕНЕРАТОРЕ;

- active resistance of coil 3 in the APPLIED GENERATOR;

Q = 20 - quality factor of the coil 3;

τ = 0.16T ₀ - time period of the closed state of the key in the APPLIED GENERATOR;

W is the maximum value of the stored electromagnetic energy by coil 3 in the APPLIED GENERATOR;

F is the frequency of the mains.

Claims (1)

A generator for inputting signal currents into a three-phase electric network containing a three-phase transformer 10 / 0.4 kV, the low-voltage winding of which Phase A is connected to the first terminal of the first inductor, the second terminal of which is connected to the first plate of the first capacitor, the low-voltage winding of Phase B is connected to the first the output of the second inductor, the second output of which is connected to the first plate of the second capacitor, the low-voltage winding of Phase C is connected to the first output of the third inductor, the second output which is connected to the first plate of the third capacitor, the first resistor, characterized in that the second, third, resistors, first, second, third diode rectifier bridges are introduced into it, and the input diagonal of the first diode rectifier bridge is connected between the first plate of the first capacitor and the low-voltage phase winding B, the input diagonal of the second diode rectifier bridge is connected between the first plate of the second capacitor and the low-voltage winding of Phase C, the input diagonal of the third diode rectifier a bridge is connected between the first lining of the third capacitor and the low-voltage winding of phase A, the plus buses of the output diagonals of the first, second, third diode rectifier bridges are connected to the input of the signal key, the negative buses of the output diagonals of the first, second, third diode rectifier bridges are connected to the output of the signal key, the second the plates of the first, second, third capacitors are respectively connected to the low-voltage windings of phase B, phase C, phase A, while the first conclusions of the first, second, third rubber Stores are combined, the second conclusions of each of which are connected respectively to the low-voltage windings of phases B, C, A, the second input of the signal key is informational.