How to judge whether the motor is good or bad by digital multimeter
1. Resistance to ground (use the high-grade ohm gear): the insulation resistance between the motor winding (three-phase) and the casing is generally required to be above 2M, and the requirement can be lowered as appropriate for use in humid, acid-base and other environments. Generally not less than 0.5M.
2. Phase-to-phase resistance (use high-grade ohms): the insulation resistance between windings of different phases is generally required to be above 2M, and the requirements can be lowered as appropriate for use in humid, acid-base and other environments, generally not less than 0.5M.
3. Three-phase resistance value (use the low gear of the ohm gear): the resistance value of the three-phase winding itself requires that the resistance value of the three-phase winding is roughly balanced (accurate data can only be obtained by measuring with a digital meter, and the requirements for different motor capacities are different. required not to exceed 2%).
220v motor how to reverse the principle
1. Schematic diagram of forward and reverse control of single-phase AC motor with reversing switch: adjust one end of the wiring of the winding connected in series with the capacitor to the other end of the power supply, and change the direction of the rotating magnetic field of the motor.
2. Centrifugal switch, running capacitor, connected to the starting capacitor to control the positive and negative rotation principle: U1U2 is the main winding of the motor, V1V2 is the built-in centrifugal switch of the motor, and Z1Z2 is the secondary winding. „V1Z1 is connected to the running capacitor (small), and V2Z1 is connected to the starting capacitor (large).
Single-phase motor generally refers to a low-power single-phase asynchronous motor powered by a single-phase AC power supply (AC220V). This type of motor usually has two-phase windings on the stator and the rotor is of the common squirrel-cage type. The distribution of the two-phase windings on the stator and the different power supply conditions can produce different starting and running characteristics.
Single-phase motor refers to an asynchronous motor that is powered by a 220V AC single-phase power supply. Because the 220V power supply is very convenient and economical, and the electricity used in household life is also 220V, so the single-phase motor is not only used in a large amount in production, but also closely related to people's daily life, especially with the improvement of people's living standards, The amount of single-phase motors used in household electrical appliances is also increasing.
In terms of production, there are micro pumps, refiners, threshers, pulverizers, woodworking machinery, medical equipment, etc. In terms of life, there are electric fans, hair dryers, exhaust fans, washing machines, refrigerators, etc. There are many types. But the power is less.
In theory, if measures are taken to make the AC current flowing in the two sets of windings of the single-phase motor have a certain phase difference, it can be started. How to make a certain phase difference between two magnetic potentials or magnetic fluxes that have been staggered by a certain angle in space is the starting point for solving the start-up problem. According to this, single-phase AC asynchronous motors can be divided into two categories: split-phase type and shaded pole type.
Split-phase single-phase motor
The split-phase single-phase motor uses capacitors or resistors in series with the inductive starting winding to play a phase shifting role, so that the current phases of the starting winding and the working winding are staggered, which is the so-called "phase splitting".
(1) Capacitive split-phase single-phase motor
Since the phase-shifting effect of the capacitor is relatively obvious, as long as a capacitor of appropriate capacity (generally about 20-50μF) is connected in series in the starting winding, the current phase difference of the two windings can be close to 90°, and the synthetic rotating magnetic field at this time is close to Because of the circular rotating magnetic field, the starting torque is large and the starting current is small.
This type of single-phase motor is widely used and can be retained (called capacitor run motor) or cut off (called capacitor start motor, which is executed by a centrifugal switch placed inside the motor) as needed after starting. If it is necessary to change the direction of rotation of the motor, it is only necessary to reverse the outlet ends of any winding, and at this time the current phase relationship of the two windings is opposite.
(2) Resistive split-phase single-phase motor
The starting winding of this kind of motor has fewer turns and thinner wires. Compared with the running winding, the reactance is small and the resistance is large. When starting with resistance phase separation, the current of the starting winding is ahead of the running winding, and the synthesized magnetic field is an elliptical rotating magnetic field with a large ellipticity, and the starting torque is small. The starting winding of the resistance split-phase single-phase motor is generally designed for short-term work. After starting, it is cut off by the centrifugal switch and maintained by the working winding.
