The motor uses an energized coil to generate a rotating magnetic field and acts on the rotor to form a magnetoelectric power rotating torque, which converts electrical energy into mechanical energy. It is widely used in the return transmission mechanism of agriculture, fishery, light industry, lifting and transportation, construction machinery and other machinery.

According to the different power supply mode, the motor can be classified into DC motor and AC motor. Pay attention to the public number "hydraulic said" to obtain more hydraulic knowledge.

The AC motor is powered by an AC power supply. The magnitude and direction of the AC power change periodically, forming a rotating magnetic field in the motor, and the magnetic field drives the rotor to rotate. The stator of the AC motor is connected to the three-phase alternating current, and the current size and direction of the three-phase alternating current change with the cycle.

The DC motor is powered by a DC power supply. The magnetic field in the motor is fixed. The Lorentz force drives the inner rotor of the motor to rotate. The current flows from the positive pole through the brush into the left side of the coil. After winding around the coil, it passes through the brush and returns to the negative pole of the power supply to form a closed loop. There is a fixed magnetic field formed by permanent magnets in the motor.

DC motors generally have brushes and commutators, while AC motors generally do not have commutators, so the structure is simple, easy to manufacture, relatively firm, and easy to make into high-speed, high-voltage, high-current, and large-capacity motors. There is often a spark between the brush and the commutator of the DC motor, which leads to the surface oxidation and even insulation of the commutator.

DC motor is mainly used for a wide range of speed control (smooth speed control) power machinery or other equipment, such as gantry planer, rolling mill, electric track traction (such as electric locomotive, subway).

The principle of AC motor is complex but the structure is relatively simple, and it is easier to maintain than DC motor. It is mainly used for power machinery or other equipment with low speed range, such as general ventilators, water pumps, machine tools, cranes on the construction site, etc.

According to the different forms of power transmission, it is divided into single motor and three-phase motor. A single-phase motor has only one phase line, and its wire is composed of a live wire and a neutral wire.

Three-phase electricity has three phase lines, and its wires are three-phase four-wire, that is, three live wires and a zero wire. Pay attention to the public number "hydraulic said" to obtain more hydraulic knowledge.

Single-phase motors are generally 220V,50HZ, and are generally used in living places, such as refrigerators, washing machines, air conditioners, electric fans, hair dryers, vacuum cleaners and other household appliances.

Three-phase motors are generally 380V,50HZ, mostly used in industrial fields, such as large fans, belt machines, hoists, etc. Generally speaking, the mechanical equipment is generally powered by the motor, and the power is generally relatively large. For high-power motors, three-phase motors are lower in cost, simpler in structure, economical and reliable, and have less vibration than single-phase motors, so three-phase motors are generally used.

With the development of power electronics technology and microelectronics technology, variable frequency motors are widely used in the field of speed control. Variable frequency motor refers to the motor equipment with high degree of mechanical automation composed of AC speed regulation mode of "special variable frequency induction motor inverter". At present, this combination mode has completely replaced the traditional mechanical speed regulation and DC speed regulation scheme.

The speed regulation principle of variable frequency motor: from the three-phase asynchronous motor speed formula: n = 60f(1-s)/p, it can be seen that changing the power supply frequency f, the pole number p of the motor and the slip rate s can achieve the purpose of changing the speed. Pay attention to the public number "hydraulic said" to obtain more hydraulic knowledge.

Compared with ordinary motors, variable frequency motors can be arbitrarily adjusted within their speed range and the motor will not be damaged, while most of the ordinary asynchronous motors can only operate under the condition of 380V/50HZ. The variable frequency motor, because the critical slip rate is inversely proportional to the power frequency, can be started directly when the critical slip rate is close to 1, so the overload capacity and starting performance do not need to be considered too much.

Variable frequency motor due to the high frequency magnetic field, so the insulation level is higher than ordinary asynchronous motor.

However, in practice, in order to save money, ordinary asynchronous motors are used instead of variable frequency motors in many occasions where speed regulation is required. Because the speed regulation accuracy of ordinary asynchronous motors is not high, the carrier frequency of the frequency converter is used when ordinary asynchronous motors are used instead of variable frequency motors. Try to be as low as possible to reduce high-frequency insulation damage to the motor.