How to use a multimeter to measure leakage voltage and distinguish between live and neutral wires
From the picture above, we can know that this multimeter can measure AC voltage, DC voltage, AC current, DC current as well as resistance and capacitance, buzzer, diode, etc. It also has intelligent anti-burn protection design, automatic shutdown, etc. , it can be said that the function is quite powerful. For an ordinary electrician, it is completely sufficient. The specific range parameters are listed in the table, so I won't go into details.
So can a multimeter be used to measure the quality of a motor? How to measure it?
I think this should be looked at from two aspects. If there is a short circuit between coils, a short circuit between turns, or an open circuit, these can be measured with a multimeter. If there is a short circuit to the ground or leakage to the ground, a megohmmeter (insulation resistance meter, megger) should be used to measure the insulation resistance value.
Let's briefly talk about using a multimeter to measure the short circuit between the motor coils and the short circuit and open circuit between the coil turns.
Motors may be large or small, but three-phase motors are composed of three windings. To determine whether the motor is faulty, measuring the resistance of the three-phase winding is essential. The resistance of the three-phase windings varies depending on the size of the motor, but the difference in resistance is not very large, generally between 2 and 5 ohms.
Usually three-phase motors have 6 binding posts, but for some smaller power ones, the manufacturer has formed a star or angle shape inside the motor, and there are only three binding posts in the junction box. The detection method of this kind of motor is the same as the detection method of 6 terminals, except that the coil turns are short-circuited, which ordinary electricians cannot detect.
Let's take the following figure as an example to detect whether there is a fault between the coils of the motor.
