Electric sockets for 380 volts are used at enterprises and in construction, as well as in private houses, at dachas or in car garages to connect welding machines, motors, compressors and equipment requiring three-phase voltage. In most cases, three-phase sockets are used to supply voltage to powerful electrical equipment. In apartments, such sockets are rare, but modern manufacturers tend to produce powerful home appliances. One condition - three-phase wiring must be present in the room.
Basic principles of connection
Connecting a three-phase outlet consists in connecting 4 (without a grounding conductor) or 5 cores, three of which will be phase, the fourth - zero, and the fifth (if any) - ground. At the time of purchasing the outlet, you need to imagine whether the plug on the device is suitable for it. If not, then it is better to buy a plug (it will be possible to change it on the equipment).
Before starting work, the voltage indicator must determine where the phases, zero and ground are located on the supply cable. It is important not to confuse, since connecting the phase to the ground or ground terminal will cause equipment breakdown and electric shock. Then turn off the power supply, make sure that it is not using the tester.
After all the work is done, you should turn on the power switch, make sure there is no phase on the case, measure the voltage between the phases - it should be 380 V. The socket is connected correctly if all conditions are met.
Types of Three Phase Connectors
Sockets of 380 volts are: four-pin - PC 32 and five-pin - 3P + PE + N. They differ in the connection scheme and the number of sockets for the plug. The circuit of the 380-volt 4-pin outlet is the same as that of the five-pin, the only thing is that the ground is not connected in the connector, but directly to the body of the electrical equipment, in this regard, it is used only for stationary equipment. Five-pin - are used for relocatable installations, and a plug connected by a flexible copper wire is connected to them.
There are still imported sockets, but they are more expensive than domestic ones. Their use is determined by design requirements, or by the presence of an appropriate plug in the device.
Another important point in the difference between outlets is the specific current for which they are designed. It is necessary that this value exceeds the maximum current of the connected electrical equipment.
Also, the sockets of the contacts 32a are divided by the method of installation on the internal and external. The internal version is in great demand, as it is convenient to operate, but their installation requires additional labor costs, namely: drilling a hole in the wall for the socket, fixing it with alabaster and mounting the socket in the installation box.
Socket 3P + PE + N
If you want to connect mobile electrical equipment, for example, a welding inverter, compressor, machine, it is recommended to use a 380-volt outlet with 5 contacts 3P + PE + N. This is usually needed in workshops, car garages and construction sites. How to connect this device?
First you need to disassemble the socket to get to the screw terminals. In this case, there will be five. According to the connection diagram of the 380 volt outlet, connect to the terminals marked as L1, L2, L3 one of the three phases in free order. The phase sequence only affects how the engine rotates - clockwise or counterclockwise. If later it turns out that the rotor is spinning in the wrong direction in which it is required, it will be possible to interchange any two phases on the switch, or on the starter. A zero is connected to the terminal labeled N. It should be noted that the contact zero is also mirrored on the plug, it is necessary to combine them. A conductor connected to a protective earth circuit is connected to the contact indicated by PE or the earth icon. The PE socket is located near the guide recess, which does not allow plugging the plug into the socket erroneously.
Socket PC32a
When it is required to connect stationary equipment (always located in one place) to electricity, for example, an electric stove, an outlet of 380 volts 32a is suitable. Three phases are connected to the three terminals of the socket L1, L2, L3, and N is the working zero. There are modifications with four contacts, but this does not mean that protective grounding is not required, it just connects directly to the metal part of the appliance body. According to the rules of electrical safety, inextricable grounding is connected to stationary equipment, bypassing a socket and cord made of copper stranded cable without insulation (for a visual assessment of its integrity). The thickness of this cord should be no thinner than the diameter of the core of the supply wire.
Deprecated Connection Method
In the past, it was possible to connect phase and zero wires to the socket terminals in an arbitrary order, and this did not adversely affect the performance of electrical equipment manufactured using the TN-C system. The only thing was that the repairmen were inconvenient when troubleshooting. Today, electrical equipment is produced that is sensitive to incorrect connection of phases and zero, so it is important not to make a mistake when connecting, otherwise a malfunction and emergency situation may occur.
In Soviet times, four-wire wiring was used, which included three phases and zero. Three-phase stationary type sockets were connected, which were marked with phase and zero icons (zero was signed with a ground icon) on the forward and reverse sides. The same designations were on the fork. These four-pin plugs and sockets are still used in work, connected according to the TN-C type, only with grounding and with the help of a five-core power cable. Where three cores will be - three phases, the fourth - zero, and the fifth - grounding.
Modern connection
The new TN-S grounding system obliges consumers to connect electrical equipment with a power cable with five cores, one of which will be grounding (PE), and the other four - as before: three phases (L1, L2, L3) and zero (N). Thus, 380 volt sockets appeared with five contacts, marked in the previous form on both sides of the connector housing.
Screw method of attaching cores to a socket
In order to connect the cores to the connector, you need to use one of the mounting options. The screw method is time-tested and very reliable. On the reverse side of the outlet there are screw clamps into which the ends of the cable are inserted and screwed to the contact. Before this, it is necessary to prepare the veins. Strip them with a sharp knife, or with a stripper, a special tool for accurately removing insulation. Put on the sleeve tips and squeeze them with a hand tool - crimper. If you do not have crimping pliers on hand, you can use a soldering iron and irradiate twisted wires. Thus, the machined ends of the cable can already be screwed to the outlet.
Screwless mounting method
This is the most modern and convenient connection, because it saves electrician time, reduces labor costs and allows you to fix a connection error.
The cable is stripped first if necessary. For information - sockets are made where the insulation does not need to be removed, it is punched with a special sharp clamp. Then the wire is placed in the socket, according to the 380 volt outlet circuit. The next step will be the simultaneous pressing of the lever and pushing the core under the clamp, and then you just need to release the handle to fix the wire. Then you need to check the strength of the connection by pulling the cable.
There is a modification of sockets, where instead of levers on each contact there are holes for a flat screwdriver. Then, placing the wire in the socket, insert a screwdriver with a flat blade into the groove, and then raise the tool handle up. At this point, cutting through the insulation will occur. It remains only to remove the screwdriver and check the strength of the contact by twitching the cable.
Wiring diagrams
The connection plan is different for different types of 380-volt sockets. Features and connections vary too. The circuit of a five-pin socket has already been considered above, now it is proposed to consider in more detail the connection of 4 contacts.
Types of old models of sockets can quite successfully be used in a modern five-wire wiring system using TN-S grounding. In this circuit, leakage current protection is provided by the PE ground wire, which is connected to the central PE ground bus. This conductor is connected directly to the electrically conductive part of the equipment case, and not to the grounding contact of the socket, which is absent in this case.
Naturally, the three-phase device must be stationary so as not to reconnect the ground.
Voltage test
To make sure that the 380 volt outlet is connected correctly, it is recommended to use a multimeter included in the AC voltage measurement mode and use the circuit.
Between phases in a free sequence, a value of 380 V should be observed. Between zero and each phase separately - 220 volts, as well as between ground (protective zero) and each phase - also 220 volts.
Only when all the values match, you can start to operate the outlet to power electrical installations. In the event of a malfunction of energy consumers, the outlet will perform the function of protection against electric shock.
There is another way to protect against current leakage - this is a special device called RCD (residual current device). It is connected immediately after the power switch, and after it comes the cable to the outlet. It will turn off as soon as a leak appears in the circuit and this will prevent a person from getting an electric shock.
By installing a differential automaton , two devices can be replaced - a power automaton and an RCD, since it performs the functions of these elements of the electrical circuit. Usually, when from the old days only a circuit breaker is present in the wiring , specialists replace it with a differential circuit breaker and all issues with protection are resolved.
Check plug connection
If the question of how to connect a 380 volt outlet, everything is clear, then how to check the plug connection in the case when they changed it. You should again use a multimeter, but put it in resistance measurement mode. The plug does not need to be plugged in yet.
The resistance of the motor windings through the plug contacts is measured. In other words, the resistance between zero and each phase contact is measured. All three values must coincide with each other, and be equal to some specific number, for example R.
Next, the series resistance of the two windings is measured. Simply put, the resistance between two phase contacts is measured in any sequence. You should get three identical values, two times larger (than in the first case), that is, 2R.
If all measurements meet the requirements, then the plug is connected correctly and it can safely be inserted into a power outlet.
The plug and socket are designed in such a way as to ensure normal operation of the transmission of the rated current of the consumer or an open circuit, but only after turning off the power switch. You can not use them to stop the supply of voltage, to avoid the occurrence of an electric arc or spark. To turn off the electrical installation, first turn off the power switch, and then unplug the plug from the outlet. To turn it on, first plug the plug into a power outlet, and then turn on the machine. The same sequence must be followed even in an emergency.