Synchronous speed The synchronous speed of a three-phase asynchronous motor is directly proportional to the power frequency and inversely proportional to the logarithm of the stator.
For example, in the formula ns=60 f/p, ns refers to the synchronous speed, with the unit of r/lmin f- frequency and the unit of Hz. The logarithm of P magnetic pole gives the rotating magnetic field speed or synchronous speed corresponding to different magnetic poles at 50Hz, 60Hz and 100Hz power frequency.
If the rotating speed of the rotor of three-phase asynchronous motor is equal to the rotating speed of the rotating magnetic field, there will be no relative motion between the magnetic field and the rotor, and the conductor can't cut the magnetic field lines, so there will be no induced potential and current in the rotor coil, and the rotor conductor of three-phase asynchronous motor will not be rotated by electromagnetic force in the magnetic field.
Piston air compressor has many structural forms. According to the configuration of cylinders, there are vertical, horizontal, angular, symmetrical and balanced and opposite. According to the compression series, it can be divided into three types: single-stage, two-stage and multi-stage. According to the set mode, it can be divided into two types: mobile and fixed.
According to the control mode, it can be divided into unloading type and pressure switch type. Among them, the unloading control mode means that when the pressure in the gas storage tank reaches the set value, the air compressor does not stop running but operates without compression by opening the safety valve. This idling state is called unloading operation. The pressure switch control mode means that when the pressure in the gas storage tank reaches the set value, the air compressor automatically stops running.
Extended data:
Classification characteristics:
Piston air compressors are generally classified according to exhaust pressure, displacement (volumetric flow), structural type and structural characteristics.
1, divided into:
Low pressure air compressor? Exhaust pressure ≤ 1.0mpa
Medium pressure air compressor 1.0mpa
High pressure air compressor? Press 10 MPa 100m3/min.
The displacement of air compressor refers to the free gas flow in the suction state.
General provisions: shaft power
3, according to the relative position of the cylinder centerline and the ground is divided into:
Vertical air compressor-the cylinder centerline is arranged perpendicular to the ground.
Angle air compressor-the cylinder centerline forms a certain angle with the ground (v, w, l, etc. ).
Horizontal air compressor-the center line of the cylinder is parallel to the ground, and the cylinder is arranged on one side of the crankshaft.
Counterweight air compressor-the center line of the cylinder is parallel to the ground, and the cylinders are symmetrically arranged on both sides of the crankshaft. /X
4, according to the structural characteristics are divided into:
Single-acting-The gas is compressed only on one side of the piston.
Double action-the gas is compressed on both sides of the piston. ?
Water-cooled-refers to the cylinder with cooling water jacket, which is cooled by water.
Air cooling-the outer surface of the cylinder is cast with fins, and the air is cooled.
Fixed-The air compressor set is fixed on the foundation.
Mobile-air compressor device is placed on mobile equipment for easy movement.
Oil lubrication-refers to the oil lubrication in the cylinder and the circulating lubrication of lubricating oil in the moving mechanism.
Oil-free lubrication-means that there is no oil lubrication in the cylinder, and both the piston and the cylinder are running dry, but the transmission mechanism is lubricated by lubricating oil circulation, and there is no oil lubrication at all-the transmission mechanism in the cylinder is oil-free.
In addition, it is divided into crosshead type (small and medium-sized oil-free air compressor) and crosshead type (V, W low-pressure micro air compressor); Single-stage compression, two-stage or multi-stage compression.
References:
Baidu encyclopedia-piston air compressor
References:
Baidu Encyclopedia-Three-phase Asynchronous Motor