In electrical engineering, there are two simple ways to connect a three-phase motor. They vary considerably, and their choice depends on the operating conditions and engine type.
The first type uses a three-phase motor connection called delta. It involves connecting the stator windings in series. In fact, the end of the first starting motor winding is connected to the second. This type of connection generates high inrush currents and allows the motor to deliver its full power rating.
The second type of connection is called a “star”. When using it, the ends of the windings are connected together, and power is supplied to their beginning. Such a connection of a three-phase motor is more gentle, but at the same time the motor produces one and a half times less power than when connected with a “triangle”.
The combined connection is considered the most correct. It is used mainly on high power engines, but it is also suitable for domestic conditions, as it protects the engine from unnecessary overloads, and at the same time it gives fullpower declared in the passport. Starts the motor using a star connection. At the same time, it will not experience large loads from high currents. After the speed reaches the nominal, it switches to the “triangle” type winding, which continues to work until the end of the work. Such a connection of a three-phase motor involves the use of a time relay or a special starter.
Separately, it is worth noting that most motors react negatively to voltage drops or short circuits. Therefore, when developing projects for connecting a three-phase motor, fusible links or entire protective mechanisms are usually included in the circuit.
Quite often, many people are faced with a situation where there is a three-phase motor available, and the electrical network has only one phase. In such cases, a three-phase motor is connected to a single-phase network using capacitors. They are connected through a free winding terminal and connected to the network. In this case, one should take into account the fact that the capacitance of the capacitors must change depending on the engine speed. Therefore, they are connected in parallel to each other in such a way that when turned on, both capacitors are in the network, and when the operating speed is reached, the second capacitor must be turned off.
Therefore, when a three-phase motor is connected to a single-phase network, the capacitor,constantly working is called a worker, and the one that turns off is called a starting one. In this case, the capacitance of the start capacitor should be approximately three times larger than the working one. The starting capacitor is connected through a separate button, which is held until the engine reaches the set speed.
It is worth noting that with such a connection, the engine loses more than 60% of its power, and if it is connected using the “star” scheme, then such a loss can increase by another one and a half times. Therefore, in such cases, it is recommended to use the "delta" scheme in order to minimize power losses.
