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Quick judgment method for electrical faults of electric tools
Date:2021/2/8 Publisher:hx2019 Hits:151
After we confirm that the power tool is an electrical fault, we still need to judge again to distinguish the general location of the fault, and try to make a quick judgment without disassembling the whole machine, which can reduce unnecessary time. Generally, experienced repairers will use it. The following methods are used to judge and distinguish quickly
 
1. Resistance method:
 
If there is no response after the power tool is plugged into the power source and the switch is pressed, the resistance method can be used to quickly judge and distinguish the general location of the fault. The resistance method is to first use the R*1 resistance file of the pointer multimeter to test the resistance of the electric tool under the condition of disconnecting from the power supply.
 
When the power switch of the power tool is not pressed (the contact is not connected), measure the resistance value between the electrodes on the power plug (measured by people of class I power tools 3 times). If the measured resistance value is 0 or close to 0, It means that there may be a short circuit or grounding between the two wires (it may be that the power switch of the power tool is damaged, the contacts are stuck, and it is affected by the circuit inside the power tool). If the measured resistance value is *, it means that the power cord is not short-circuited Failure, you can continue to find other failure points
 
Note: This step cannot be omitted,
 
2. When the power switch of the power tool is pressed (the contact is turned on), measure the resistance between the L and N levels on the power cord plug. If there is a certain resistance value, the internal circuit of the electric tool motor is unblocked. , You can power on to test whether the machine is running. If there is no resistance value, it means that there is an open circuit in the internal circuit of the motor of the electric tool.
 
3. Unscrew the brush holder cover with a flat-blade screwdriver, remove the brushes from the two brush holders, and press the power switch (the contacts are turned on). Measure the resistance between the two blade electrodes of the power plug base (except for the grounded blade electrodes) and the two brush holder steel bases, if the resistance values ​​measured twice are the same, the stator coil and the rotor are connected symmetrically , It means that the power cord, power switch, and stator coil are all good, and the fault of the power tool may be in the brush or rotor part. For example, the two measured resistance values ​​are seriously different, and the stator coil and the rotor are connected together, or explain There is poor contact or one of the coil packages of the stator coil is poorly welded or has a serious short-circuit failure,
 
4. Remove the handle shell of the power tool. At the entry point of the power switch, test whether the power line is stagnant or open. If there is no open circuit fault, continue to find the fault point
 
5. You can press the power switch (the contact is on) to measure the resistance value of the contact group corresponding to the power switch of the electric tool.
 
6. Measure the resistance value of the two connection points at the outlet of the power switch and a brush holder copper holder (actually measure the resistance value of the two coils of the stator). If the resistance value is equal, it means that the stator coil is not faulty. If the resistance value is Severe short-circuit failure,
 
7. If the electric tool has not found any problem after the above steps, the center eye caused by the two brushes of the two meter pens can be inserted into the surface of the commutator (actually, the diagonal resistance of the rotor is measured. Value) If there is a certain resistance, the rotor may be good, and most of the faults are poor contact of the brushes.
 
Note that when using an electronic speed governor or electronic speed control switch in the circuit, you need to short-circuit the part and measure it after other circuits, otherwise it will be mistakenly judged as an open circuit fault, and the above steps should be followed after short-circuiting. If no problem is found, it is the fault of the electronic speed governor and the electronic speed control switch itself, and it can work normally after replacing it with a new one.