Scheme of connection of the actuator
At the heart of all or, at least, the majority of schemes of start of the asynchronous electric motors used very widely both in the industry and in normal life, very simple scheme lies. That electrician who does not know it is bad.
So, all scheme, except the electric motor which is installed directly on the specific equipment or the device is mounted either in the guard, or in the special box (PML).
The START-UP and STOP buttons can be as on the front party of this guard, so out of it (are mounted on site where it is convenient to manage work), and maybe there, and there, depending on convenience. Three-phase tension from the closest place of powering is brought to this guard (as a rule, from the distribution board), and from it there is already the cable going on the electric motor.
And now about the principle of work. On the F1, F2, F3 plugs three-phase tension moves. Start of the asynchronous electric motor requires operation of the magnetic actuator (PM) and short circuit of its contacts of PM1, PM2 and PM3. For operation of PM it is necessary to give tension on its winding. By the way, its size depends on the coil, that is on what tension it is expected. It also depends on conditions and the place of operation of the equipment. Coils happen on 380, 220, 110, 36, 24 and 12 V). This scheme is expected the voltage of 220 V as undertakes from one of the available phases and zero.
Giving of power supply on the coil of the magnetic actuator is carried out on such chain. With f1 the phase on normally closed contact of thermal protection of the TP1 electric motor arrives, further passes through the coil of the actuator and comes to the START-UP button (KH1) and to contact of self-pickup of PM4 (the magnetic actuator). From them the power supply comes to the STOP normally closed button and later becomes isolated on zero.
For start it is required to press the START-UP button then the chain of the coil of the magnetic actuator will become isolated and will attract (will close) contacts of PM1-3 (for launch of the engine) and contact of PM4 which will give the chance at release of the button of start-up to continue work and not to switch-off the magnetic actuator (is called self-pickup). For the stop of the electric motor it is required to press only the FEET button (KH2) and by that to break off the PM coil feed circuit. As a result contacts of PM1-3 and PM4 will be turned off and work will be stopped before the following start of Start-up.
For protection thermal relays (on our scheme it is TP) are surely put. At the overload of the electric motor current raises and the engine sharply begins to heat up, up to failure. This protection works at increase in current on phases, thereby disconnects the contacts of TP1 that is similar to pressing of the FEET button.
These cases happen generally at full jamming of the mechanical part or at the big mechanical overload in the equipment on which the electric motor works. Though it becomes frequent the reason and the cursor, because of the dried bearings, the bad winding, mechanical damage, etc.
Connections of the actuator according to the scheme the reverse
The version of the stated above scheme of the actuator by the simplified option is used for start of the electric motors working in one mode i.e. without changing rotation (pumps, tsirkulyarka, fans). But for the equipment which has to work in two directions (frame cranes, telphers, winches, opening closing of gate, etc.) other circuitry is necessary.
For such scheme we need not one, but two identical actuators and the START-UP-FEET button three-push-button, i.e. two START-UP buttons and one FEET. The reverse panels and on two buttons can be used in schemes, on sites where work intervals very short. For example, for the small winch with intervals of work of 3-10 seconds. For operation of this equipment option on two buttons more suitable, but buttons both starting, i.e. only with normally open contacts, and interlock contacts (pm1 and pm2) self-pickup are not involved in the scheme. While you hold the button pressed, the equipment works as released the button - the equipment stopped. For the rest the scheme the reverse is similar to the scheme the simplified option.
Connection of the actuator according to the scheme the star - the triangle
Switching of the engine from the star on the triangle is applied to protection of electric circuits against overloads. Generally switch from the star to the triangle powerful three-phase asynchronous engines from 30-50 kW and high-speed ~ 3000 RPM, sometimes 1500 RPM.
If the engine is connected in the star, then on each its winding voltage of 220 Volts moves and if the engine is connected in the triangle, then voltage of 380 Volts is the share of each its winding. Here the Ohm's law of I=U/R comes into effect: the tension is higher, the current is higher, and resistance does not change.
In other words, at connection in the triangle (380) current will be higher, than at connection in the star (220).
When the electric motor accelerates and gains whole revolutions, the picture completely changes. The matter is that the engine has the power which does not depend on that, it is connected in the star or in the triangle. Engine capacity depends more on iron and the section of the wire. Here other law of W=I*U electrical equipment works.
Power is equal to the current intensity increased by tension that is the tension is higher, the current is lower. At connection in the triangle (380) current will be lower, than in the star (220). In the engine the ends of windings are brought to "terminal block" in such a way that, depending on how to put crossing points, connection in the star or in the triangle will turn out. Such scheme is usually drawn on the cover. To make switchings from the star to the triangle, we instead of crossing points will use contacts of magnetic actuators.
The scheme of connection of the three-phase asynchronous engine in which starting provision windings of the stator connect the star, and in working situation — the triangle.
Six ends approach the engine. The KM magnetic actuator serves for inclusion and shutdown of the engine. Contacts of the magnetic KM1 actuator work as the crossing point for turning on of the asynchronous engine in the triangle. Pay attention that wires from the terminal block of the engine have to be included in the same order, as well as in the engine. The main thing - not to mix.
By pressing the PUSK button the power supply moves on the KM magnetic actuator. It works, and on it tension via the interlock contact moves. Now the button can be released. Further tension moves on RV timing circuit, it counts the determined time. Also tension through the live contact of the timing circuit moves on the magnetic KM2 actuator, and the engine is started in "star".
Through the determined time RT timing circuit works. The magnetic P3 actuator is switched-off. Tension through contact of the timing circuit moves on normally closed (closed in the disconnected situation) the interlock contact of the magnetic KM2 actuator, and from there on the coil of the magnetic KM1 actuator. And the electric motor turns on in the triangle.
The KM2 actuator should be connected also via the normally closed block contact puskatelyakm1 for protection against simultaneous turning on of actuators.
It is better to take magnetic KM1 and SQ.KM actuators doubled with mechanical blocking of simultaneous inclusion.
The scheme is disconnected by the STOP button.
- Automatic cut.
- Three magnetic KM, KM1 actuators, SQ.KM.
- The button start-up - stop; - Current transformers TT1, TT2; - RT current relay; - RV timing circuit.
- BKM, BKM1, BKM2-interlock contacts of the actuator.