The asynchronous motor is powered by a three-phase AC network. For operation, a delta and star connection can be used. In order for everything to work stably, it is necessary to use special jumpers created for this, be it a star or delta connection. These are the most convenient options for connection and, accordingly, have a high degree of reliability.
Content
- Differences between connections
- Star connection
- Triangle scheme
- Star and triangle combination
- Additional Tips
Differences between connections
First you need to find out what is the difference between a star and a triangle. If we approach this issue from the point of view of electrical engineering, then the first option allows the engine to run more smoothly and gently. But there is one moment: the engine will not be able to reach full power, which is presented in the technical plan specifications.
The delta connection allows the engine to reach maximum power in a short time. Therefore, the efficiency of the device is applied to its full capacity. However, there is a serious drawback, which is the high inrush currents.
The fight against such phenomena as high starting currents is to connect a start rheostat to the circuit. This makes it possible to start the engine much smoother and improve its performance.
Star connection
Star connection is that the ends of all 3 windings are reconnected to a common point called neutral. If a neutral wire is available, then such a circuit is considered four-wire, in its absence, it is three-wire.
The beginning at the conclusions is fixed to certain phases of the power supply network. The voltage that is applied to these phases is 380 volts or 660 volts. The main advantages of such a scheme include:
- Non-stop operation of the engine for a long time and with stability.
- Decreasing the power of the equipment increases the reliability and operating time for the star circuit.
- Thanks to this connection, the start of the electric drive has increased smoothness.
- It is possible to influence the parameters by short-term overload.
- During operation, the equipment case will not become accessible for overheating.
There is equipment with a connection of the windings inside. Since only three pins are placed on the block of such equipment, other connection methods cannot be applied. Such execution does not require qualified specialists.
Triangle scheme
Instead of a star circuit, you can use a delta connection, the essence of which is to connect the ends and beginnings of the windings in a sequential manner. The end at the phase C winding closes the circuit and creates a whole circuit. Due to this shape, the resulting circuit will be more ergonomic.
Each of the windings has a line voltage of 220 or 380 volts. Of the main advantages of the circuit, there are:
- The power of the electric motors reaches the highest value.
- Applying a suitable rheostat for a smoother start.
- Significantly increased torque.
- High tractive effort.
A triangle is used in such mechanisms where significant starting loads and energy are required for powerful mechanisms. A significant torque is achieved by an increase in self-induction EMF indicators. This phenomenon is caused by large flow currents.
Star and triangle combination
If the structure is of a complex type, then the combined method of a star and a triangle is used. The use of this method leads to the fact that the power is greatly increased. But in the case when the engine cannot match the technical characteristics, everything will overheat and burn out.
To reduce the line voltage in the stator windings, a star circuit should be used. After decreasing the flowing current, the frequency will start to increase. A relay contact type circuit helps to switch delta to star.
It is this combination that gives the greatest reliability and significant productivity of the equipment used without fear of failure. This scheme is effective for engines where a lightweight starting scheme is involved. But with a decrease in the starting current and a constant moment, it should not be used. An alternative is a phase rotor with a rheostat for starting.
Additional Tips
The current during engine start is 7 times the operating current. Power is one and a half times higher when connected with a delta, a smooth start is obtained with the help of frequency-type wires.
The star connection method requires taking into account the fact that it is necessary to correct phase imbalances, otherwise there is a risk of equipment failure.
Linear and phase voltages with a triangle are equal to each other. If you want to connect the engine to the household network, then you need a phase-shifting capacitor. Thus, the use of a delta or star circuit depends on the design of the motor and the requirements of the household network. Therefore, you should carefully look at the engine performance and the necessary parameters that need to be increased for more efficient operation of the structure.
