Fault detection method of resistance-linked circuit

The resistance parallel circuit is a basic parallel circuit. All the circuits in charge can be transformed into resistance series and resistance parallel circuits to understand the working principle. Parallel circuit and series circuit have completely different characteristics. They are completely different circuits, and they cannot be equivalent to each other (resistance parallel circuit diagram).

The picture shows a resistor parallel circuit. It can be seen from the picture that the R1 and R2 pins of the resistor are connected to form a parallel circuit of two resistors. +V is the DC working voltage of this circuit. When R1 and R2 are connected in parallel in an AC circuit, the circuit form remains unchanged, but the DC voltage +V is changed to an AC signal. When analyzing the resistance parallel circuit, it is necessary to understand the following resistance parallel characteristics.

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The characteristic that the total resistance of the parallel circuit becomes smaller as it gets smaller is the opposite of the total resistance of the series circuit. If two 20KΩ are connected in parallel, the total resistance after the parallel connection is half of one of the resistances, which is 10kΩ. As shown below. After the parallel connection, the total resistance R<R1<R2.

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Note: In a resistor parallel circuit, the reciprocal of the total resistance value R after the resistors are connected is equal to the sum of the reciprocals of the resistors participating in parallel, the formula is: 1/R=1/R1+1/R2+1/R3.. ....

2. The total current of the parallel circuit is equal to the sum of the current of each branch (the schematic diagram of the current of each branch of the parallel circuit)

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As shown in the figure, the current I1 flowing through the resistor R1, the current flowing through the resistor R2 is I2, the total current I of the parallel circuit, the current flowing from the power supply +V is divided into two paths, one flowing through R1 and the other flowing through the resistor R2. The sum of the currents of each branch is equal to the total current in the loop. For this specific circuit, it is I=I1+I2. If there are more parallel branches, I=I1+I2+I3...... In each branch of the parallel circuit, the current in the branch and the resistance of the resistor in the branch In an inverse relationship, a resistor with a large resistance has a small current in the road, on the contrary, a resistor with a small resistance has a large current in the circuit.

From the formula I=U/R, it can be known that when the current of resistor R1 is less than the current flowing through R2, as shown in the figure below:

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Parallel circuit current characteristic memory diagram:

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is represented by a river. The water flowing out of the reservoir is divided into 3 ways, and all flows into the sea, which is equivalent to the current flowing out of the power supply flowing into each resistance circuit branch.

3. Characteristics of equal voltage at both ends of the parallel resistors In a parallel circuit, the voltages on the parallel resistors are equal (as shown in the figure below), because the two resistors R1 and R2 are connected in parallel, so the voltages on them are equal. If there are more resistors in parallel in the circuit, then the voltage across the resistors in parallel will be equal.

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4. The main contradiction in the parallel circuit is the resistance of small resistance. In a parallel circuit, if the resistance of a certain resistor is much larger than the resistance of other resistances, the resistance will not play a major role, and it can be considered as an open circuit. This leaves a small resistor in the circuit. When analyzing a parallel circuit, it is necessary to grasp a resistor with a small resistance value. It is the main contradiction in this circuit. Even if a resistor with a small resistance value plays a major role in a parallel circuit, this is exactly the opposite of a series circuit.

5. Resistance parallel circuit open circuit and short circuit fault detection method:

1) The open circuit fault detection method is as follows:

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When the circuit is powered off, use a multimeter to measure the total resistance of the parallel circuit. Under normal circumstances, the measured total resistance value should be <R1 <R2.

If the measured resistance value is greater than any of R1 and greater than R2, it means that R1 or R2 in the circuit is open. Specifically, which circuit is open must be analyzed, or you can measure the current of the branch without each resistor. Make judgments.

2) The short-circuit fault detection method is as follows:

If the total resistance measured is zero, it means that there is a short circuit in the parallel circuit. If you need to understand the detailed location and reason, you need to go further. Measurement. This is of great significance for troubleshooting. It determines the scope of the faulty circuit and also determines the direction of the inspection.