SU1723539A1 - Device for continuous testing of zeroing circuit electrical safety - Google Patents

Abstract

The invention relates to a measuring and measuring technique and can be used for continuous monitoring of the integrity of the neutralizing conductor of a four-wire cable. OBJECTIVE OF THE INVENTION The invention relates to an instrumentation technique and can be used to continuously monitor the integrity of the semiconducting conductor of a four-core cable. A device for monitoring the operability of mobile and portable electrical installations, including a power cable with a conductor connected to an electrical receiver body, a capacitor connecting the power supply phase to an electrical receiver body, is used to increase electrical safety of electrical equipment operation. The goal is achieved by introducing a capacitor 8, the terminals of which are connected in parallel to the terminals of the coil 4 of the magnetic starter to create a resonance of currents, the values of the inductive resistance of the coil and the capacitor capacitance are from the mathematical relationship given in the description of the invention. The device contains a power cable 1, a leading conductor 2, an electric receiver 3, a closing button 5 Start a magnetic starter, a block contacts 6 of the magnetic starter, a disconnecting button Stop 7 of the magnetic starter, power contacts 9 of the magnetic starter. The positive effect is to increase the electrical safety of electrical equipment operation by limiting the current passing through the person to a small value in the event of a broken circuit when the person touches the receiver and presses the Start button of the magnetic starter. 1 il. A relay is connected at the output of an amplifier fed by a DC source, a step-up transformer, the primary winding of which is connected to the power supply cable, and the secondary winding is connected to the input of the amplifier 1.. A disadvantage of this device is the low level of electrical safety during operation of electrical installations due to the transfer of dangerous potential through a capacitor connecting the phase of the mains supply to the body of the electrical receiver 1 GO CJ with CJ o

Description

when the core wire is broken; the device does not provide human security when it is touched to the case of the consumer due to the complexity of the device containing the step-up transformer, amplifier, and an additional power source of the amplifier.

In addition, monitoring the integrity of the zoning circuit is not reliable enough, since the executive relay can be triggered not only in the event of a break in the core conductor, but also in the event of a malfunction of the amplifier or power supply, which causes a false disconnection of the receiver, i.e. leads to a decrease in the reliability of power supply to consumers.

The closest in essence to the proposed device is the control circuit and protection of an individual electric drive with control circuits connected to the phase voltage 2.

A disadvantage of this device is the dangerous removal of potential to the body of the electric receiver when the circuit is broken and the Start button of the magnetic starter is pressed, while the device does not provide human safety when it touches the body of the electric receiver, and the magnetic starter may not be disconnected when the circuit is broken. deadly current through man.

The aim of the invention is to increase the electrical safety of electrical equipment operation by reducing the potential transfer to the electrical receiver body in case of a vanishing circuit and when a person touches the electric receiver body and pressing the Start button of the magnetic starter, and due to reliable control of the zero circuit when a person flows through the person significantly less current.

The goal is achieved by the fact that, parallel to the coil of the magnetic starter, a capacitor is additionally introduced, whose capacitance with the inductive resistance of the coil to create current resonance is in the ratio

 3200 XL t R2 + xi:

where C is the capacitance of the capacitor, μF; R is the active resistance of the actuator coil, Ohm; XL is the inductive resistance of the actuator coil. Ohm

A device is known for monitoring the resistance of a grounding circuit.

five

0

five

0

five

0

five

0

five

ac machine, containing resonant circuits connected to the grounding 3.

In the known device, resonant circuits consisting of series-connected capacitors and inductors and connected at the ends of the cable to its power conductors are tuned to the resonance of voltages for high frequency and serve to delay the operating frequency of 50 Hz.

In the proposed device, the resonance of currents is created by the inductance of the coil of the magnetic actuator and the capacitor capacitance, the resonant circuit is tuned to a frequency of 50 Hz and serves to increase the resulting resistance of the current circuit.

The drawing is a schematic diagram of a device for continuous monitoring of the integrity of the nulling circuit.

The device contains a power cable 1 with a leading conductor 2 connected to the body 3 of the electric receiver, a magnetic starter, the coil 4 of which is its first clip through the closing button 5 Start, shunted by the closing block contact 6 of the magnetic starter, disconnecting button 7 Stop is connected to the same power phase cable 1, and the second clip - to the case of the electric receiver 3, a capacitor 8 connected in parallel to the coil 4 of the magnetic starter, and the capacitance of the capacitor 8 with inductive resistance of the coil 4 of the magnetic starter d generating resonance currents are in the ratio

from 3200 XL

R2 + X

The device works as follows.

With a total zagging conductor 2 of the power cable 1 by pressing the button 5. Starting the magnetic starter turns on the phase voltage, operates, closes its auxiliary contact 6 and the power contacts 9, connecting the electrical receiver 3 to the mains.

If during operation the integrity of the zagging circuit (in particular, the control conductor) is violated, the coil 4 of the magnetic starter is de-energized, the block contacts 6 and the power contacts 9 open, the electrical receiver 3 is de-energized, while the potential on the electrical receiver 3 is zero .

If at the same time a person touches the case of an electric receiver, then due to the creation by pressing button 5 of the start of a magnetic starter a closed circuit: phase of the power cable 1, button 7 Stop, button 5 Start, a resonant circuit consisting of a coil 4 of the magnetic starter and a capacitor 8 , the case of the electric receiver 3, the resistance of the human body Rh, the earth - a person with a resistance Rh will flow some current, However, due to the presence of a resonant circuit (coil 4, capacitor 8), this current is reduced to a significantly smaller value.

When using a PME-211 type magnetic starter, the turn-on voltage of the UBWI starter is 130 V, the turn-on current is on, 0.4 A; disconnection voltage of the actuator Watchl 70 V; shutdown current 1 off 8mA.

When the starter is off and its magnetic circuit is open (air gaps in the W-shaped core rods are about 7 mm) Rkat 175 Ohm, HKat 250 Ohm, coil impedance Z 2 300 Ohm.

The shunt capacitor has a capacitance C 0.7 µF, the capacitance of the XCond3 is 4500 Ohm, and the coil-capacitor does not have a significant effect on the resulting parameter values.

When the magnetic starter is turned on and when its magnetic circuit is closed, if there is no shunting coil of a capacitor actuator with a capacitance of C 0.7 μF (that is, prior to the introduction of the proposed invention), the effective resistance value of the coil P cat is 1450 Ohms (a significant increase in Rkat is a consequence of significant increase the magnetic induction in the steel of the coil core and, accordingly, the occurrence of significant losses in the core), the total resistance of the coil Z 4350 Ohms, the inductive resistance of the coil X cat 4100 m.

When connecting a shunt capacitor with a capacitance of 0.7 µF, R Var 12900 ohms, the full reactive resistance of the coil and the capacitor according to the parallel replacement circuit X ".

In accordance with the foregoing, the following modes may occur:

1. Without introducing the invention.

but). The unit operates in the normal mode (the magnetic starter is on, its magnetic circuit is closed), the person is in contact with the case of the power receiver.

b). A rupture appeared in the chain of conductors of the supply cable.

The person (who is in electrical connection with the earth) is connected to the circuit, which is under a 220 V phase voltage, through a coil

magnetic starter, electrical receiver body to the ground. The current is established through the person

Ih220

 ma,

V (1000 4-1450) 2 +41002

very dangerous for humans. However, the magnetic starter is not disconnected in this case, since this current (46 mA) is much higher than the tripping current of the magnetic starter (8 mA).

The electromechanism will continue to work normally (with a break in the vanishing circuit), and the person will be under the influence of this very dangerous current for him for an indefinitely long time (until the supply voltage is turned off or the Stop button of the magnetic starter is pressed).

2. With the introduction of the invention.

In the same situation, a person will be in a circuit connected in series with a much larger and almost purely active resistance of the resonant circuit. The coil of the actuator is a capacitor with a capacitance of 0.7 F, while R Var 12900 Ohm, X oohm and the current passing through the person , will be only 15-16 mA, which is close to safe (10 mA).

The main reason for increasing the active resistance of the coil of the magnetic actuator and the capacitor at the resonance of currents in it to 12900 Ohms and, accordingly, reducing the current through a person to 15-16 mA is a large effective value of the resistance of the coil of the magnetic actuator in the closed state of the actuator magnetic circuit (РГкат 1450 Ohm), arising, as mentioned earlier, as a result of a significant loss in the steel of the coil core in its closed state.

The current through a person in the considered emergency situation in the presence of the proposed technical solution can be reduced to a completely safe value (less than 10 mA) while reducing the losses in the steel core of the coil at least twice.

This can be achieved in any of the following ways, or a combination of them:

- Using thinner sheets when assembling an actuator core (e.g., about 0.3-0.25 mm thick instead of 0.5 mm thick sheets currently used);

- The use of higher quality steel (with lower specific losses);

Claims (1)

- Reduction of the air gap in an open core (for example, from 7 to 5 mm) and, accordingly, a decrease in the required values of magnetic inductions both in the open state of the core and in its closed state. Claims The device for continuous monitoring of the integrity of the zeroing circuit, comprising a power cable with a negative conductor connected to the body of the electrical receiver, a magnetic starter whose coil 0 with its first clip through the closing button the Start, shunted by the closing contact of the magnetic starter, the disconnecting Stop button is connected to one phase of the power cable, and the second clip is connected to the case of the electrical receiver, in order to improve the electrical safety of electrical equipment operation a capacitor, the terminals of which are connected in parallel to the terminals of the coil of the magnetic actuator to create a resonance of currents.