Motor before use, or in the fault, should be measured first under the motor is good or bad, before you can energize and use.
How to judge a motor is good or bad, there are two main parameters, one is to measure the motor coil resistance, the second is to measure the insulation resistance of the coil and shell. Three-phase motors and single-phase motors measure insulation resistance in the same way, but the measurement of coil resistance judgment method is not the same.
Three-phase motors
Three-phase asynchronous motors, commonly used in work, are composed of three sets of coils, and most of the coil connections are Y-type hairpin or △ hairpin.
Three-phase motor schematic
Motor terminal Box
To determine whether the coil of a three-phase motor is good or bad, it is necessary to measure whether the resistance between the three-phase windings is balanced. Do not need to know the corresponding power of the motor actual resistance of each group of coils, and do not need to remove the connecting piece to measure the resistance of the three groups of coils to determine the balance of the resistance of the three-phase coil winding, which is more cumbersome.
Whether it is a Y-type connection motor, or △ connection motor, or two-speed motor. Can be used to measure the resistance of U1, V1, W1 terminals between each other, the same can determine whether the motor three-phase resistance balance.
Measurement of motor coil resistance usually use a multimeter, multimeter gear selection in the resistance 200Ω file, with red and black pens to measure the motor (U1, V1), (V1, W1), (U1, W1) between the resistance value.
multimeter
When the mutual error between the measured resistance values is 2%, it can be judged that the motor resistance value is normal. When the error between the measured resistance value reaches 10% or more, it can be judged that the motor is bad.
When the measured resistance error in 2% -10%, to consider the motor coil is not the original production, or later motor coil burned out over the rewinding of the coil, replace the coil maintenance personnel level problems, winding the coil resistance error, when the error is not too large, can also be used normally. When you are not sure, you can use the inverter to drive the motor to see if there is any alarm phenomenon to determine the motor is good or bad.
When the motor coil resistance value of three-phase balance, can not say that the motor is good, but also to measure the insulation resistance of the motor, the general motor insulation resistance is lower than 0.58MΩ, indicating that the motor insulation is not good, should not be used. Motor insulation resistance is higher than 0.58MΩ, indicating that the motor insulation is good, can be used normally.
When measuring the motor with a multimeter, the multimeter gear in the resistance MΩ file. A pen on the U1, V1, W1 any terminal, another pen on the motor shell, pay attention to ride in the absence of paint, the measured resistance is greater than 0.58MΩ or not pass, you can judge the motor insulation is normal. Measured resistance is less than 0.58MΩ, insulation is not good, should not be used. Multimeter to measure the insulation resistance of the motor is not necessarily accurate, when the feeling of each measurement of the insulation resistance of the motor are not the same value, affecting your judgment. You can use megohmmeter, the data measured by multimeter has only reference value, while the value measured by megohmmeter is more accurate and can be taken as real data.
Megohmmeter E, L terminal, access to the wire rod, the two wire rod measurement with the multimeter pen to measure the motor in the same way, megohmmeter no gear adjustment, as long as the 120 revolutions per minute to shake the hand crank can be.
Single-phase motors
Single-phase motors usually have only two sets of coils, the main winding and the secondary winding. The secondary winding starts and the main winding runs. Inside the motor, the main winding and the secondary winding are connected in series, and a wire is drawn from the connection. Single-phase motors usually draw three wires, which can be indicated by ① ② ③ three wire ends.
Single-phase motor coils and wiring
Use the 200 ohm file of multimeter, when the motor power is small, you can improve the ohm file of multimeter.
Use the multimeter to measure the single-phase motor ① ② ③ three wires, you can choose two two-phase measurement, ① ②, ② ③, ③ ① to measure the resistance value of the three groups, the measured resistance value of the normal 1 big 2 small.
When measured 2 groups of small resistance value is not equal to the maximum resistance value to prove that the motor is damaged, or measure the resistance of infinity, to prove that the motor winding damage, single-phase motor main winding and secondary winding is intertwined, short-circuit is the main winding and secondary winding short-circuit together, a group of short-circuits occurring in the winding phenomenon is rare.
2 groups of small resistance value sum for the largest resistance value, prove that the motor coil winding is normal.
Single-phase motor should also measure the insulation resistance, measurement and three-phase motor, please refer to the above three-phase motor insulation resistance measurement method, insulation resistance higher than 0.58MΩ to prove that the insulation resistance of the motor is normal, the insulation resistance is lower than 0.58MΩ to prove that the insulation of the motor is not good should not be used.
General measurement of resistance value of the smallest resistance value for the main winding, the second largest resistance value for the secondary winding, the largest resistance value for the main and secondary winding series resistance.
Single-phase motor wiring for the measurement of the largest resistance line and capacitance in parallel, the measurement of the smallest resistance line into the single-phase voltage.
When measuring the single-phase motor resistance value of 1 large 2 small, when the two small measured resistance value is the same, that the main and secondary winding resistance value is the same, when the main winding is energized motor for positive rotation, when the secondary winding is energized motor for reverse rotation. When the main and vice winding resistance values are the same, it means that the single-phase motor has the function of forward and reverse rotation and can be used for forward and reverse rotation.
