18 Tips for Electricians

The 18 tips for electricians are as follows:

1. How to use a low-voltage electric test pen to determine AC single-phase circuit faults

Use an electric pen for AC electric test, and the light is the live wire Not brightly.

Circuit faults can be checked, and fire and ground can be measured when power is turned on.

It lights up and goes off normally to check the equipment, and the circuit disconnection is not suspicious.

If both ends do not light up, the live wire of the power supply has been disconnected.

If both ends are bright, the neutral line is broken or separated.

2. How to measure DC voltage with a pointer multimeter

Zero should be adjusted before measurement, and the range should be selected appropriately.

Determine the positive and negative poles of the circuit, and make sure the parallel connections are clear.

The black test lead should be connected to the negative pole, and the red test lead should be connected to the positive pole.

If the hands of the meter rotate in the opposite direction, the positive and negative polarity of the wiring should be reversed.

3. How to measure DC current with a pointer multimeter

Zero should be adjusted before measurement, and the range should be selected appropriately.

Determine the positive and negative poles of the circuit, and make sure the series wiring is clear.

The black test lead should be connected to the negative pole, and the red test lead should be connected to the positive pole.

If the hands of the meter rotate in the opposite direction, the positive and negative polarity of the wiring should be reversed.

4. How to measure the DC resistance of a conductor with a pointer multimeter

Measure the resistance and select the range, and then adjust to zero after selecting the range.

If the two pens are short-circuited, look at the meter needle and adjust it if it is not at zero.

Turn the ohm zero-adjustment knob until the watch hand reaches zero.

The knob still has a certain number. Replace the battery and adjust again.

The contact must be good, and both hands should be suspended in the air.

To ensure accurate measurement, the needle of the meter should be in the grid.

After the measurement is completed, turn off the power and turn the knob to the voltage.

5. Use a pointer multimeter to judge the quality of the capacitor

A multimeter can make a rough judgment on the quality of the capacitor.

Use the resistor multiplied by the K gear, and connect the test leads to one extreme.

The hands of the watch swing to close to zero, and then slowly return.

When you reach a certain place and stop, the more you return, the healthier you will be.

When it reaches zero, there is a short circuit, and when it returns to zero, there is leakage.

The measuring meter does not move at first, and the internal circuit of the capacitor is broken.

6. Estimation of the weight of a kilometer of conductor

The weight of a kilometer of conductor depends on the cross-section and type.

The cross-section unit is millimeters square, multiplied by the coefficient The values ??are different.

Duralumin is the lightest at 2.8, followed by pure aluminum at three times.

The steel core aluminum strand times four, 7.8 iron is heavier.

Pure copper weighs eight point eight points, and steel strand weighs nine point zero.

Consider sag and lashing, and multiply that by one point and three.

Related formula: Mass = Density X Volume

Volume = Base area >The wire cuts the magnetic lines, and the induced electromagnetic force is generated inside.

When a wire is connected to a closed circuit, current will flow through it.

Use your right hand to determine the direction of flow. Extend your right hand to form a flat surface.

The conductor moves toward the thumb, with the palm of the hand facing the N extreme.

The direction of the four fingers is the current, and this end is also the positive end.

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8. Use an electric pen skillfully to perform low-voltage nuclear phase verification:

To determine whether the two wires are the same or different, hold a pen in each hand, and

insulate the two feet from the ground. , two strokes each touch an important line.

Look at a pen with your eyes. If the same phase does not light up, it is different.

9. Kirchhoff’s first law and second law

Kirchhoff is a celebrity, and he invented the circuit law.

The node current is the first, and the outflow and inflow phases are equal.

The circuit voltage is the second, and the voltage drop and potential are equal.

10. Magnets and their properties, magnetic fields and magnetic lines of force

Regardless of size and thickness, magnets have two poles.

South Pole S and North Pole N, the maximum magnetic force at both ends.

Like poles repel and opposite poles attract, everything is the same.

Describe magnetic field lines, each of which is a closed line.

Pass from N to S pole outside the body, and from S to N inside the body.

The lines do not cross each other and are relatively densely packed at both ends.

11. Filter circuit set up to reduce output current ripple

To obtain a stable flow, the filter circuit is connected to the output.

A capacitor and a resistor are connected to form a T-shaped circuit.

Two capacitors and one reactance are called pie circuits.

There is also a simpler one, two capacitors and one resistor.

12. Determine AC and DC current:

The electric pen determines AC and DC, AC is bright and DC is dark,

AC tube is bright and DC tube is bright. One end.

13. Tips for wiring the motor:

Add three to 2.5, add four to 4; add six after 6, 25 five; 120 wires, match hundreds.

14. Tips for calculating current according to power:

Double the electric power and half the electric heating. Single phase kilowatt, 4.5A. Single phase 380, current two and a half amps.

15. The relationship between impedance, reactance, inductive reactance and capacitive reactance:

The resistance of the inductor to the flow is called the inductive reactance, and the resistance of the capacitor to the flow is called the capacitive reactance.

Inductance and capacitance are connected in series, and inductive reactance and capacitive reactance combine with reactance.

Resistance, inductance, and capacitance are connected in series, and resistance and reactance add up to impedance.

Each of the three is one side, with hooks, strands, and strings arranged in order.

The Pythagorean Theorem can be used to find one side given both sides.

16. The definition formula of neutral current, phase current, line voltage and phase voltage of three-phase power supply:

Three-phase voltage is divided into phases and lines. Fire zero is the phase and fire is the live wire.

The three-phase current is divided into phases and lines, and the windings are divided into phases and live wires.

17. If the capacity of the transformer is known, find the rated current on the voltage level side.

Use a coefficient for common voltages, and multiply the tolerance coefficient to get the current.

Rated voltage is 400 volts, coefficient is 1.445.

The rated voltage is 6,000 volts, and the coefficient is 0.096.

The rated voltage is 10,000 volts, and the coefficient is exactly 0.6.

18. Parallel operation of two transformers

To run two transformers in parallel, four conditions must be met.

The wiring groups must be the same and have the same transformation ratio.

The impedance voltages must be consistent and connected in the same phase sequence.

The difference in capacity should not be much, preferably no more than three to one.