Connecting a 380 volt electric motor with a capacitor

Consider at first why it is considered that the engine is powered by 380 volts. Happiness to be three phases at 220 volts. The simplest questions make newcomers float away, the lack of knowledge of the theory gives rise to practical errors. We are sincerely grateful to the enthusiasts who have thrown YouTube with educational videos, without such a rich material it is difficult to give practical advice to those who are planning to connect a 380-volt 380 volt motor with a capacitor. We proceed to the implementation of the theory in practice.

Engine operation 380 volt

These engines are called three-phase. They are distinguished by a bunch of advantages over typical household, widely used by industry. Advantages relate to high power, efficiency. It is in three-phase motors that it is possible to dispense with starting windings, capacitors with the appropriate power supply. Constructions can eliminate unnecessary elements. Start-up relay of the refrigerator, which closely monitors the integrity, time of operation of the starting winding. Three-phase motors do not need home-grown tricks.

work. Why is this happening? The presence of three phases can create a rotating electromagnetic field inside the stator without additional tweaks. Let's see the drawing. For the sake of simplicity, the rotor is shown, equipped with two poles, the stator contains a coil per phase of alternating current. Configurations of typical 380 volt engines are more complex, simplification does not hurt to explain the essence of the processes occurring inside.

Picture in blue shows negatively charged fields, in red - positive. At the initial moment the stator is devoid of a mark, the three coils are white. The rotor in our assumption is made of permanent magnets, painted and resides in an arbitrary position. There are only two poles. Then we move according to the diagrams:

1. The first picture awarded phase B with a negative sign, the other two are slightly positively charged( approximately one third of the amplitude), schematically shown in a pale pink color. The positive pole of the rotor has shifted to coil B. The weak positive field AC has attracted the south pole of the rotor. Since the charge level is the same, the center of the pole is exactly in the middle.
2. At the next point in time( after 60 degrees, 3.3 ms), the south pole appears in phase A of the stator. The rotor rotates 60 degrees clockwise. Weak negative fields of phases B, C hold the rotor positive pole between them.
3. At this moment the north pole of the stator is located at phase C, the rotor continues to rotate another 60 degrees. Further picture should be clear.

As a result of the correct distribution of the three phases, the stator field rotates, dragging the rotor. The speed does not match the network 50 Hz. The stator windings are larger, the number of rotor poles is different. In addition, there is the phenomenon of slippage depending on the voltage amplitude, and many other factors. Nuances are used to regulate the speed of rotation of the motor shaft. The question of the voltage of 380 volts was reached. Formed in three phases with a current voltage value of 220 volts( as in the outlet).Take the difference between any two at an arbitrary point in time, the value exceeds the specified value.

It turns out 380 volts. A three-phase motor uses three voltages for operation with a current value of 220 volts, the shift between any one is 120 degrees. You can easily trace from the graph in our figure. That is why many are tempted to use the equipment at home, run, using one phase supplied by the outlet. Directly impossible to make, as it should be clear, you have to invent tricks. The simplest is the use of a capacitor. Passing capacitance changes the voltage phase by 90 degrees. The difference is less than 120, who wanted to get in the ideal.

In practice, connecting a motor through a capacitor works fine. True for the implementation of ideas have a little tricky.

Three-phase 380V motor starting from

home network

First, you need to know how electrical switching of the windings is performed. Typically, the motor housing is provided with a protective cover to hide the electrical wiring. It is necessary to remove the shield, proceed to study the scheme. More often, the electrical connection diagram is shown. In order to start up to produce a three-phase network, star switching is used. The ends of the three windings have one common point, called the neutral, the opposite side is supplied with phases. One for each winding. It turns out the field distribution discussed above.

Connecting the asynchronous motor 380 to 220 Volt, try switching to change. Useful electrical circuit driven nameplate housing. According to the figure, the motor windings are joined by a triangle. Each at both ends is combined with the other. Let's see what happens. What distinguishes the technique from the regular use of equipment. For simplicity, the figure shows the switching circuit of the capacitor. It looks like this:

• A 220 V mains voltage is applied to the winding C.
• The voltage comes to winding A through the working capacitor in the phase shift state by 90 degrees.
• On the winding B is the difference between the indicated voltages.

Let's look at the diagrams: what it will look like in practice. The phase shift is uneven. Between the peaks along which the epures are plotted, 90 and 45 degrees are set aside. As a result, the rotation is in principle devoid of opportunities to be uniform. The shape of the phase of the winding is different from sinusoidal. The launch of a three-phase motor with a network of 220 volts is accompanied by the presence of energy loss. The process is possible. There is often a phenomenon called sticking. Incorrect field shape inside the stator is powerless to unwind the stator.

The motor connection scheme is somewhat simplified, it differs from the standards for the execution of design documentation drawings. The visibility of the picture is obvious. The circuit capacitor is working, it is found starting. Need to strengthen the torque at the initial stage. Any asynchronous motor at the start consumes more current, a lot of energy is spent on the first movement. The capacitor is usually connected parallel to the worker, is included in the circuit by pressing a special button. For example, it is suggested to mark as Acceleration.

When the shaft gains momentum, the starting capacity becomes unnecessary, and the resistance to movement of the shaft decreases. Releasing the Accelerate button, we exclude the element from the network. In order for the starting capacity to be discharged( the voltage is able to reach 300 V), we short-circuit the resistance through which the current will not flow in working condition. Gradually the electrons are compensated, the danger of defeat will disappear. There is a simple question - how to choose a working, starting capacity? Connecting a 380 V electric motor to 220 V is not an easy task. Let's consider the answer.

Choosing the values ​​of the starting capacitance for connecting a three-phase 220 V motorAmong the starting and operating capacitors, exclude components with an operating voltage below 400 volts. Practice imposes corrections, it is necessary to do it by hand. Pay attention to the wires. The currents according to the technical documentation are given relative to the voltage of 220 V. The considered circuit uses other values. You may have to recalculate the size of the currents.

In practice, if the working capacity is too small, the shaft “sticks”.The engine would work if given initial acceleration, if the beast with a power of 4 kW pootryvayet fingers, no one to blame. It turns out that the nominal working capacity is determined by at least two parameters:

Adjustment of the engine

1. A more powerful engine, a larger capacitor rating needs to be applied. At 250 watts, dozens of microfarads are enough, with greater power, the value is in the hundreds. It is logical to stock in advance a solid set of capacitors. It is advisable to take film, electrolytic without special measures is prohibited to use, designed to work in DC networks. At connection of an alternating voltage of 220 V can simply blow up.
2. Higher engine rpm, higher starting capacitor rating required. Reaching the difference several times, we increase the capacity value by an order of magnitude( 10 times).To start the engine with a power of 2.2 kW and 3000 rpm, try to stock up on a battery of 200–250 microfarads. Very great value. The capacity of the globe is fractions of mF.

Strongly the capacity of the starting capacitor depends on the applied load. The pulley motor consumes a lot of energy, the battery volume increases. Let's try to choose the nominal. Practitioners have noticed: the more stable the 380 V motor works, powered by a single-phase network, when the voltages in the capacitor arms are equal. We avoid touching the winding working directly from the network, we measure the potential of the other two. How does the capacitance value determine the voltage?

Asynchronous motor is characterized by its own reactance. When enabled, a divider is formed. Beautifully plotted, in practice, the shape of the phases is very different. Determined reactance by the above set of parameters. The design of the engine, causing the size of the power, speed, shaft load. A number of parameters, which cannot be taken into account theoretically in the framework of the review. Therefore, practitioners simply recommend first finding the minimum size of the battery at which the motor starts to rotate, then gradually increase the nominal value until the winding voltages become equal.

After engine spin-up, it sometimes turns out that equality has been broken. The resistance to the movement of the shaft has fallen. Before you connect the electric motor from 380 to 220 finally, decide on the working conditions, try to ensure the specified equality.

Please note: the actual value can exceed 220 volts. The voltage value will be 270 V. Before you connect the motor through a capacitor, worry about the contacts. Ensure a reliable connection in order to avoid losses, overheating in the places of current flow. Switching is better to lead to special terminals, tightening the bolts. After the final selection of parameters, the electrical part should be closed with a casing, the wires should be passed through the rubber seal of the side wall of the compartment.