Principle of megger:
There are three terminals on the megger: one is "L" which is the line terminal, one "E" is the line terminal. ground and the other "G" is For the shield end, the correct connection method is: the end of the wire "L" is connected to the conductor of the equipment under test, the ground terminal "E" is connected to the shell of the grounded equipment and the "G" end of the shield is connected to the insulating part of the equipment under test.
Because the insulation degree between the internal wire of the "E" terminal and the shell is lower than that between the "L" terminal and the shell, when the megger is placed on the ground and used In the correct wiring method, the "E" "The insulation resistance between the terminal and the instrument shell and the shell and ground is equivalent to a short circuit and will not cause errors.
When "L" and "E" are connected reversely, the insulation resistance of "E" to ground is connectedin parallel with the measured insulation resistance, which makes the measurement result smaller and results in a larger error. the measure.
Detailed information:
Shaker Notes:< /p>
1. It is prohibited to measure insulation resistance during lightning or near high voltage equipment. It can only be measured when the equipment is not charged and there is no induced electricity.
2. When measuring the insulation resistance of the equipment, the power supply to the equipment should first be turned off. Equipment containing inductors and capacitors should be discharged first. Off-duty personnel must request corresponding work tickets before they can work.
3. The oscillator must be placed horizontally. AvBefore wiring, you need to shake the oscillator and observe whether the pointer is at "∞". Then short-circuit terminals L and E and slowly shake the watch. The needle should be at zero. After open circuit and short circuit tests, the megger is confirmed to be intact before measurement can be made.
4. The megger wire should be a multi-stranded soft wire and the two wires should not be twisted together to avoid inaccurate measurement data.
5. After the megger measurement is completed, the measured object should be unloaded immediately. Before the megger stops rotating and the measured object is discharged, do not touch the measuring part of the measured object or. disassemble it with your hands to avoid electric shock.
Baidu Encyclopedia - Shake Meter
Can the electricity emitted by a 500V shaker decompose water?
The result is: the measured value may be greater than thereal value.
The measurement must reach 120 revolutions per minute. The megger relies on the internal DC generator to produce the voltage, then relies on the feedback current to calculate the resistance value. If the speed does not reach the rated value, the output voltage decreases and the feedback current decreases accordingly. on the megger, it is actually the reverse scale of the current, so the resistance value read is higher than the actual value.
How to measure 380V water pump motor insulation? How good is the insulation?
Yes. 500 volt stirrer, inside the meterThe DC voltage generated by the DC generator is 500 volts. Current intensity and voltage are the key factors that affect the speed of water decomposition. Higher current and voltage will cause the rate of water decomposition to accelerate. Usually, 48V direct current is le direct current. Solution. The safe voltage level range of water and the DC voltage of 500 volts are greater than 48 volts, so the electricity emitted by the 500 V meter can decompose the water.
"Crank alternators are often used as power sources for crank meters." Why is this sentence wrong?
Use a 500V or 1000V megger to measure, if the insulation resistance is 0.5MΩ or more, it is qualified.
A megger, also known as a megger, is an instrument used to measure the insulation resistance and high value resistance of equipment under test. It consists of a hand-cranked generator, a meter head and three. terminals (i.e. L: line end, E: ground end, G: shield end).
Before measuring, perform an open circuit and short circuit test on the megger to check whether the megger ist in good condition. If both connecting wires are open and the handle is shaken, the pointer should point to ∞. (infinity). Momentarily short the connection head and the pointer should point to 0. At this time, it means the meter is good.
Connect the L terminal (line end) of the megger to the water pump motor terminal box and connect the E terminal (ground end) of the megger to the water pump motor housing. water.
When measuring, press the meter housing with one hand (to prevent the meter from vibrating). When the needle indicates 0, stop shaking immediately to avoid burning the meter;
When measuring, place the meter in a horizontal position and turn the generator crank at a speed of about 120 revolutions per minute
The reading after the pointer is basically stable after shaking for about 1 minute, this is the insulation resistance value of theengine.
A megger, also known as a megger, is an instrument used to measure the insulation resistance and high value resistance of equipment under test. It consists of a hand-cranked generator, a meter head and three. terminals (i.e. L: line end, E: ground end, G: shield end).
Principles of selection of megohmmeters:
(1) Selection of the rated voltage level. Generally speaking, for equipment with a voltage rating below 500 V, a 500 V or 1000 V megger should be used; For equipment with a rated voltage above 500V, a 1000V~2500V megometer should be used. For equipment with a voltage rating greater than 10 KV, a 2500 V megger should be used.
(2) Resistance range selection. There are two small black dots on the scale of the megger dial, and the area between the small dots noirs is the precise measurement area. Therefore, when selecting a table, the insulation resistance value of the equipment under test should be within the precise measurement area.
3. Precautions for using meggers
(1) The megger should be selected according to the voltage level of the equipment. For low voltage electrical equipment, a 500 volt. The megger must be selected. Using a megger with too high a voltage to measure low voltage insulation may cause insulation breakdown;
(2) Before measuring insulation resistance, the power supply of the equipment under test must be turned off. off and a short circuit discharge must be carried out. The purpose of discharge is to ensure the safety of people and equipment,And make the measurement results accurate;
(3) The connection of the megometer should be two separate single wires with good insulation (ofpreferably two colors). The two wires should not be twisted together, this is better. do not put the connection in contact with earth to avoid errors caused by poor insulation of the connection;
(4) Before measurement, perform an open circuit and short circuit test on the megger to check whether the megger is in good condition. If both connecting wires are open and the handle is shaken, the pointer should point to ∞ (infinity). At this time, if the two connecting wires are momentarily short-circuited, the pointer should point to 0. At. this time the pointer should point to 0.
Shake the handle. The meter must be in good condition, otherwise the meter will have errors;
(5) When measuring, press the meter shell with one hand (to prevent the meter from vibrating) . When the needle indicates 0, stop shaking immediately to avoid burning the meter;
(6) When measuring, place thee counter in the horizontal position and rotate the generator at a speed of approximately 120 revolutions per minute. handle;
(7) Before the megger stops rotating or the equipment under test is discharged, do not touch the measured part and the terminal of the instrument or remove the connection with your hands to avoid electric shock;
p>(8) If the weather is humid or the insulation resistance of the cable is measured, the shield terminal G (or protective ring) should be connected to eliminate the influence of the leakage current on the surface of the insulation;
(9) It is prohibited to use a megohmmeter to measure the insulation of equipment in lightning or humid weather and when there is high voltage electrical equipment nearby;
( 10) After the measurement is completed, the equipment under test should be unloaded.
4. The role of measuring insulation resistance and judging the resistance value:
The measurementure of the insulation resistance of electrical equipment is the simplest auxiliary method to check its insulation condition. The measured insulation resistance may reveal defects such as foreign bodies affecting the insulation of the conductive part of the electrical equipment, moisture and dirt on part or all of the insulation, strong deterioration of the insulating oil, breakdown of the insulation and significant thermal aging.
(1). The measured insulation resistance must be equal to or greater than the generally admissible value. The specific regulations of various electrical appliances are different: 0.5MΩ for low voltage equipment. 300 MΩ for 3-10 KV and 300 MΩ for 20-35 KV 400 MΩ, 63-220 KV corresponds to 800 MΩ and 500 KV corresponds to 3000 MΩ.
(2) Compare the measured value with the value from the factory, shed and previous years. There should be no significant changescompared to the previous test result, usually not less than 70% of the previous value. .
(3) The absorption rate of transformers of 35 kV and above should be measured, which is generally not less than 1.3. (Absorption rate calculation: insulation resistance measured in 60 seconds is better than insulation resistance measured in 15 seconds).
A megohmmeter is a megohmmeter. It contains a manual generator. The generator voltage is very high. After rectification, it charges the high voltage capacitor inside. -Voltage capacitor as power source. If the voltage is insufficient, it means starting the generator by hand and the generator voltage is higher than 200V.
The high DC voltage generated by the internal battery as a power source and the DC/DC conversion flows from pole E through the product under test to pole L, thus producing A current is generated from pole E to pole L, andAfter I/V conversion, the divider completes the operation and directly displays the measured insulation resistance value on the LCD screen.
Detailed information:
Place the megger in a horizontal position during shaking measurement. There is no short circuit between the tremolo end knobs when it rotates. The handle should be shaken slowly and gradually. If the pointer is at zero, this means that the measured insulation may have a short circuit. At this time, the handle cannot continue to be shaken. To prevent the coil inside the watch from heating up and being damaged.
Once the reading is complete, discharge the device under test. The discharge method involves removing the ground wire used when measuring the megger and shorting it to the device under test (no discharging the megger).