Confirmation of three-phase motor connection
Update:04 Nov 2021
Summary:There are two types of wiring for three-phase motors: star connection and delta connection. From a theoretical point of ...
There are two types of wiring for three-phase motors: star connection and delta connection. From a theoretical point of view, these two connection methods can be selected at will, and there will be no difference in the analysis and calculation results. In practical engineering applications, this too simple "choose one out of two" proposition is quite reasonable. The question of how to choose or how to determine often plagues sales and marketing service personnel. Today, Ms. Shen described the wiring of the motor and related issues in detail. Let's look at the twists and turns of simple propositions. They are confusing and crazy.
In my country, according to the power division, the general series three-phase motors are star connection, 3KW or more is angle connection; YVF variable frequency series motors are star type, and 45KW or more is angle connection; YZ, YZR, YZP series crane metallurgical motors adopt star connection connect. The above are all the practice of asynchronous motor stator connection, customers and manufacturers can also adjust according to actual needs. In fact, the above regulations reflect that the choice of star connection or corner connection is a bit special. The choice of connection method differs depending on the type or purpose.
Due to the limitation of the grid capacity, the starting current of a series three-phase motor is usually limited. The current base value of the motor of 3kW and below is small, and the starting current is not enough to cause an impact on the power grid. The star connection helps to block the flow of asymmetrical current and harmonic current, so it is stipulated that the star connection means that the starting current of kW and above motors begins to affect the grid. The greater the power, the greater the impact on the grid. In order to reduce the starting current, a reduced voltage starting method must be adopted. The angle-connected three-phase motor can realize the step-down starting of the star-delta conversion. The general six-terminal outgoing series motor is simple and economical to realize.