The most direct feature of asynchronous motors is that there is a difference between the actual speed of the motor and the speed of the magnetic field, that is, there is a slip; compared with other performance parameters of the motor, the slip of the motor is the easiest to obtain, and any motor user can use some simple The operation is calculated.
In the expression of the performance parameters of the motor, the slip rate is a relatively important performance parameter, which is characterized by the percentage of the slip relative to the synchronous speed. of. For example, a power frequency 2-pole motor with a slip rate of 1.8% and a 12-pole motor have a large difference in actual absolute slip. When the slip rate is the same as 1.8%, the slip of a 2-pole power frequency asynchronous motor is 3000 × 1.8% = 54 rpm, the slip of a 12-pole power frequency motor is 500 × 1.8% = 9 rpm. Similarly, for motors with different poles with the same slip, the corresponding slip ratios will also be quite different.
From the comparative analysis of the concepts of slip and slip, slip is an absolute value, that is, the absolute difference between the actual speed and the synchronous magnetic field speed, and the unit is rev/min; while the slip is the difference between the slip and the synchronous speed . percentage.
Therefore, the synchronous speed and actual speed of the motor should be known when calculating the slip. The calculation of the synchronous speed of the motor is based on the formula n=60f/p (where f is the rated frequency of the motor, and p is the number of pole pairs of the motor); therefore, the synchronous speed corresponding to the power frequency 2, 4, 6, 8, 10 and 12 The speeds are 3000, 1500, 1000, 750, 600 and 500 rpm.
The actual speed of the motor can be actually detected by the tachometer, and it is also calculated according to the number of revolutions per minute. The actual speed of the asynchronous motor is less than the synchronous speed, and the difference between the synchronous speed and the actual speed is the slip of the asynchronous motor, and the unit is rev/min.
There are many types of tachometers, and electronic tachometers are a relatively general concept: rotational speed measurement tools designed and manufactured based on modern electronic technology generally have sensors and displays, and some also have signal output and control. Different from the traditional photoelectric speed measurement technology, the inductive tachometer does not need to install a photoelectric sensor, no motor shaft extension, and can be used in the water pump industry and other industries where it is difficult to install sensors.
Post time: Mar-30-2023