The faults of electric tools are generally divided into electrical faults and mechanical faults. Electrical faults generally refer to the problems and faults of power supply, switches and other related electrical parts. How to distinguish electrical faults from mechanical faults? We have said last time: the distinguishing methods of electrical faults and mechanical faults of electric tools

After we confirm that the electric tool is an electrical fault, we still need to judge and distinguish the general location of the fault again, and try our best to judge quickly without dismantling the whole machine. This can reduce unnecessary time. Generally, experienced maintenance technicians will use the following methods to judge and quickly distinguish

1. Resistance method:

If there is no reaction after the electric tool is inserted into the power supply and the switch is pressed, the resistance method can be used to quickly judge and distinguish the general position of the fault. In the resistance method, the R * 1 resistance of the pointer type multimeter is used to test the resistance of electric tools without power supply,

When the power switch of the electric tool is not pressed (the contact is not connected), measure the resistance between the electrodes on the power plug (the common people of class I electric tools measure it three times). If the measured resistance value is 0 or close to 0, it indicates two wires There may be a short circuit or grounding between them (or the power switch of the power tool is damaged, the contact is stuck, which is affected by the circuit inside the power tool). If the measured resistance value is *, it means that the power line has no short circuit fault, and you can continue to find other fault points

Note: this step cannot be omitted,

How to quickly judge the electrical fault of electric tools

2. When the power switch of the electric tool is pressed (the contact is connected), measure the resistance value between the level L and the level n on the plug of the power line. If there is a certain resistance value, it indicates that the internal circuit of the motor of the electric tool is unblocked and the machine can be energized to test whether the machine operates. If there is no resistance value, there is an open circuit in the motor internal circuit of the electric tool,

3. Screw off the brush holder cover with a slotted screw driver, take out the brush from the two brush holders, and then press the power switch (the contact is connected). Measure the resistance value between the two plug-in electrodes (except the grounded insert electrode) and the two brush holders. If the resistance values measured twice are equal, and the stator coil and rotor are symmetrically connected, it indicates that the power line, power switch and stator coil are all good. The fault of electric tools may be in the brush or rotor part, such as the resistance value measured twice In case of serious difference, the stator coil and the rotor are connected together, or it indicates that there is contact discomfort or one of the stator coils is not welded properly or there is serious short circuit fault,

4. Remove the handle shell of the electric tool. At the incoming line of the power switch, measure whether the power line is open circuited. If there is no open circuit fault, continue to find the fault point

5. You can press the power switch (contact on state) to measure the resistance value of the contact group corresponding to the power switch of the electric tool. If both groups are 0, it indicates that the power switch is good, then the fault point can be found intermittently,

6. Measure the resistance values of two connection points at the outlet of the power switch and a brush holder copper base (actually, the resistance values of the two coils of the stator are measured). If the resistance values are equal, it means that there is no fault in the stator coil. For example, the resistance value is a serious short circuit fault,

7. If no problem is found in the electric tool after the above steps, the center eye caused by two brushes of the two probes of the meter can be inserted into the surface of the commutator (actually, the diagonal resistance of the rotor is measured). If there is a certain resistance, the rotor may be good, and most of the faults are poor contact of the brush,

Note: when electronic speed regulator and electronic speed control switch are used in the circuit, it is necessary to measure the device after short circuit connection or other circuits, otherwise it will be misjudged as open circuit fault. After short circuit connection, the above steps should be followed. If no problem is found, it is the electronic governor. The electronic speed control switch can work normally after replacement.