Connection of the single-phase motor to a household three-phase network: options and main mistakes

In the process of living in a private or country house, the owner at some point decides to install a backup power supply. Most often it is a generator. Although the purchase of this device is quite a difficult task, this is not the end of the difficulties, faced by the owner of a private household. No less simple task for him is to connect the generator to the house.

Perhaps, most will believe, that there should be no special problems: after all, it is enough to start the generator, connect it to the house and then you can not know the worries. It should be noted, that the process of connecting home generators is a rather complex measure, during which it is quite easy to make serious mistakes, which can eventually lead to big trouble. And the breakdown of the generator is the smallest of them.

In this article we will pay attention to the features of connecting a single-phase generator to the house, where the wiring is laid, designed for three-phase network. Let it seem strange, however, even experienced electricians often have difficulties, when they have to solve a similar problem. And they create problems for themselves, which in general could be decided to avoid at the initial stage.

The principle of operation of a single-phase motor

The basis of the device of the classical single-phase motor is formed by two windings, which are at right angles to each other. Each of them has its own purpose, what is meant by their name:

• home;
• auxiliary.

These windings may include several sections, determined by the number of poles.

Deciding to use an asynchronous single-phase motor to connect to the house, you have to remember that first, that it has certain limitations. The capabilities of the stator are embedded in its design, which determines, for which tasks it can be used. It's about that, that when creating each motor are taken into account in advance, which of the tasks will be most important to him: ensuring maximum efficiency, torque, duty cycle, etc..

Such asynchronous motors create a higher noise level during operation, than two-phase analogues, due to the presence of a pulsating field. At the engine with two phases this lack is shown to a lesser extent, because they are equipped with a starting capacitor. It is the latter device that creates the conditions for smooth operation of the motor.

Asynchronous single-phase motors require compliance with certain rules of their operation, than they stand out against three-phase analogues. Ignition of single-phase motors in the "idling" mode is considered inadmissible. Working at low loads leads to their strong heating. Optimally, when such an engine is running under load, which is more 25% from full.

The right approach to solving the problem

You can simplify the task of connecting the generator to the house as much as possible: for this purpose it is enough to allocate a certain group of the most responsible consumers during construction of a country or private house and performance of electric installation works., which will be provided with backup power supply. This group is most often used to supply electricity to:

• lighting;
• heating equipment;
• certain sockets;
• security and fire alarm.

This option is attractive because, that to solve the problem you can use a fairly low power engine.

But, Unfortunately, only a few owners of country and private houses do so. The most common situations, when the problem of buying a motor for a three-phase network of the house and its connection becomes especially relevant at that time, when you have to face such an unpleasant phenomenon, as power outages.

The homeowner is often unable to solve this problem, because he has no special knowledge, to choose a suitable version of the motor and in accordance with the established requirements to perform work on its connection to a three-phase network. To even a man, which is far from the sphere of electricity, was able to understand, what exactly to do and how, we will not resort to special deadlines and other difficulties, and try to explain everything this way, so that anyone can understand the essence of these works.

Options for connecting a single-phase motor

How to start connecting a single-phase generator to a three-phase network of the house? First of all it is necessary to be defined with a connection method, many of which are known today. I want to start their consideration with that, which we have already mentioned above - by connecting the engine to the allocation for this purpose to a group of consumers. This method is basic, however, there are others besides it.

Load connection in manual mode

You can also connect the engine with a toggle switch, switch on 3 positions 1-0-2. According to the given scheme, each position will correspond to the following:

• "1" - will understand the load, requested from the industrial city network;
• "0" - the translation of the switch in this position will mean, that is disabled;
• "2" - will correspond to the load, provided with a backup source of electricity. Gasoline will act as such, diesel or gas generator.

We will not dwell in detail on the arrangement of the components, truth, I want to note, that the breaker or three-position switch has a fairly simple design, which includes fixed contacts, connected to the wires (load-city-generator), and moving contacts, whose task is to ensure the switching of the load from the city to the generator and back.

If there is a problem to switch the three-phase load city-load, then there is the involvement of three phases. What is meant here, that three city phases A-B-C are fed to the circuit breaker, they go to the load. In order for the load to be transferred to the generator, we must do such manipulations, that as a result on each of phases electricity was exposed.

This problem can be solved by slightly improving our circuit breaker switch: on the other side, where the generator will be connected, you will need to install a jumper between phases A-B-C. further, when the load will be applied to the generator, each of the phases will be supplied with electricity.

Load connection via contactors

Along with the above methods, you can connect a single-phase motor by using contactors. The main role here will be played by two contactors, among which one will provide power to the load from the city grid, and another will help shift the load to an alternative source of electricity, which will be the generator. It is advisable to use this method only in that case, if the system has automatic backup power.

When the load is created by the city network, then each of the phases, which is connected to the contactor, will go to the load. When the generator appears in the system, do the same, as with the flip switch: on the contactor terminals there, where the cable is connected, coming from the generator, will have to place a jumper between the phases and A-B-C.

Switcher or contactors?

If you are not considering the option of installing an automatic generator control system, then in this case to effectively solve the problem you will need to install a flip switch. And this device must be three-position 1-0-2. If you decide to use the automatic start unit of the AVR generator, then the only option for you will be the use of contactors.

The operation of a single-phase motor has one important nuance: this backup power supply is able to ensure the smooth operation of all devices, having one phase. Therefore it is necessary to be convinced, that the devices you have in the house meet this requirement. If you find three-phase units, you will have to disconnect them from the power supply, while you use the generator. Otherwise, you risk losing them completely, as their use in such a connection may cause them to fail.

Actions, leading to irreparable consequences

Generator, whether gas or gasoline, differs from most other devices in that, that traditional connection schemes are applied to it. Particular attention should be paid to the most serious mistakes, which are able to disable this backup power supply.

The wiring diagram is considered invalid, in which the generator is connected to a three-phase network directly to the consumer.

It is also forbidden to connect using two machines, among which the first is connected to the household mains, and the other directly to the generator. It should be borne in mind, what a mistake to make here is very easy, as a result, the wrong machine will be included. The consequences of such an action will be terrible, therefore it is not necessary to bring business to such.

Conclusion

Despite the misleading impression, to connect a single-phase electric motor to a three-phase network is not so simple. Considering, that you can use several methods for this, and each of them has its own characteristics, such work must be performed by a specialist. After all, any mistake, allowed when connecting this backup power supply, can lead to that, not only the generator itself will fail, but also devices, who are not designed to work in such a relationship.