How to distinguish induction from leakage, we will teach you three tricks! Ordinary people can also learn super practical
When household appliances (such as washing machines, refrigerators, power tools) have a leak or induction electrification, they will feel "hand numbness".
If it is only induced electricity, these appliances can continue to be used. If it is a leak, continuing to use it will be very dangerous and needs to be repaired.
But how to correctly distinguish induction charging from a real leak?
Inductive electrification is caused by mutual induction between internal circuit and shell of machine, or mutual induction between line and line, which is equivalent to connection between charged part and shell through a capacitance.
Current leakage occurs due to aging or reduction of insulation of internal circuit due to long-term use of machine or dampness, which causes machine body to become electrified.
Some of them are caused by deformation of machine body, which results in one or more direct contacts between body and internal live parts (in which case it is dangerous to reuse machine).
01 Resistance measurement method
Use a multimeter to measure insulation resistance between machine frame and line. If measured resistance is greater than 1 MΩ, it can be considered as inductive charging.
When measured resistance is a few thousand ohms or less, it may be considered a leak and appropriate action must be taken.
This is a simpler method than most commonly used one, but it is unreliable and needs to be further validated by other methods.
02 load estimation method
Turn off zero line (N line) of machine, connect a 220V/15W light bulb between breakpoint and case, and connect power after connection is good. If light comes on, it means machine is leaking.
If light does not come on, then machine is charging by induction. This is because leakage current can be large enough to make bulb glow, but induced current is only a few tens of milliamps, which is not enough to make bulb glow. This method is more accurate in estimation.
03 Voltage measurement method
(1) Use multimeter's voltage block to measure voltage between machine frame and ground, and then swap live wire (L wire) and neutral wire (N wire). machine, measure voltage between machine frame and ground again.
If there is a large change in two voltage values before and after, it is largely caused by leakage; if there is no obvious change in results of two measurements, this means that it is induced charging.
This is because machine's leak point is often not in middle of a normally charged machine body. If it is in middle, solution will be wrong, and results of two measurements and after will be different.
When induction is charged, value will not change as it has nothing to do with measurement point.
(2) When machine is running, first use a multimeter to measure voltage between machine body and neutral line (N line). Stop machine, disconnect neutral wire (N wire), connect a multimeter between break point and machine body, then only connect live wire (L wire) to power supply, measure voltage again, and compare two times before and after, if results are two times If there is an obvious change, this indicates a leak.
If there is not much change, in most cases it is electrification caused by induction. This is because voltage measured for first time is voltage between leakage point and neutral line (line N) (unless leakage point is very close to end of live wire, it is approximately equal to voltage of power supply), and voltage measured for second time is basically onpower supply voltage; they often differ from each other. If it is induction charging, there will be no such numerical change.
(3) Turn DMM to AC20V gear, then take test lead in one hand and keep other test lead close to machine body. When distance is about 4-5 cm, observe multimeter, if multimeter shows a voltage of several volts (V), this indicates that charging is caused by leakage.
If multimeter does not show or shows a very small value, it means that case is charging due to induction.
Based on above several methods of judgment, some of them are simple and some are not very accurate, so when faced with case of loading car body, several methods should be used interacting with each other to improve reliability of decision, so take appropriate measures.
When distinguishing whether it is a leak or an induction charge, different measures must be taken.
If it is an induction charging, you must connect ground wire to machine body, so that there will be no "hand numbness" phenomenon in future, and also play a role in protecting machine from leakage.
If electrification is caused by a leak, machine should be repaired to find leak, and machine can only be used after insulation has been strengthened or repaired.
- What is drowning in gold? Why Shen Jin?
- This is a metaphor for EMI/EMS/EMC that can be understood at a glance.
- How many types of pads have you seen in PCB design?
- Summary of Common PCB Repair Techniques
- What is three anti-paint? How to use it correctly?
- Knowing these rules, you will not get confused looking at circuit diagram.
- How to make anti-interference PCB design?
- Can diodes do this?