Determination of stator connection method for three-phase asynchronous motor
The connection method of the three-phase asynchronous motor has two types: a star connection method (hereinafter referred to as a star connection) and a delta connection method (hereinafter referred to as a corner connection). From the perspective of theoretical theory, the two methods can be arbitrarily chosen, and there is no difference in the analysis results.
The connection method of the three-phase asynchronous motor has two types: a star connection method (hereinafter referred to as a star connection) and a delta connection method (hereinafter referred to as a corner connection). From the perspective of theoretical theory, the two methods can be arbitrarily chosen, and there is no difference in the analysis results.
In the actual application of engineering, this too simple alternative to the proposition is quite a bit of a statement. How to choose or how to determine the problem often plagues sales people and market service personnel. Today, Ms. Shen said that the motor connection and related issues are open to explain, let's take a look at the simple propositions of the answers that are confusing and confusing.
In China, the general-purpose series motors are in accordance with the power boundary, 3kW and below power motors are star-connected, and 3kW or more is specified as corner joints; YVF inverter series motors 45kW and below power motors are star-connected, 45kW or more are angled; and for YZ, YZR For the series of lifting metallurgical motors such as YZP, the star connection is adopted. All of these are the conventions for asynchronous motor stator connection, and customers and manufacturers can also adjust according to actual needs. The above regulations actually reflect the fact that the selection of stars or corners is a bit more stressful, with different types or different uses, and the choice of connection is different.
Due to the limitation of grid capacity, the general-purpose series motors usually have to limit the starting current of the motor. The base value of the power motor of 3kW and below is small, and the starting current is not enough to impact the power grid. The star connection helps to block the asymmetrical current. The current of the wave current is stipulated, and the starting current of the motor of 4kW and above starts to affect the power grid. The greater the power, the greater the impact on the power grid, the lower the starting current has to be adopted to reduce the starting current, and the angled motor can be Achieving star-delta conversion and step-down start-up, the universal series of motors with 6-terminal output is easy to implement, simple and economical.
The starting process of the variable frequency power supply drive motor is actually a soft start, the starting current will not exceed twice the rated current (the inverter capacity limit), and the starting has no effect on the power grid. Therefore, the 45kW and below power motors are all star-connected; for YZ, YZR, YZP and other series of lifting metallurgical motors, the operational reliability of the motor is in the first place, the star connection is the most ideal; the permanent magnet motor must use the star connection, in order to eliminate the harmonic magnetic field induction in the magnetic field established by the permanent magnet Current. High-voltage motors are mostly star-connected, with more safety and reliability factors.
Relationship between voltage and current parameters under star connection
The connection selection problem is solved. The phase voltage, line voltage, phase current and line current under the corresponding connection method also have various ways to make people faint.
Consequences of the wrong connection
For a two-voltage running motor, the stator requires six outlet ends, with a star connection at high voltage and a corner connection at low voltage. If there is no special request from the customer, it is recommended that the motor manufacturer adopts the star connection method to prevent the customer from being burned due to improper pressure applied by the customer.
