Push-button station - a device for local and remote control circuit coil circuits, contactors, relays, motor circuit. Sometimes referred to as push-button stations.
According to the definition button post contains 2 - 5 buttons. It is the engine management system on the forward stroke and a reverse or lift:
- way down;
Push-button station is recognized by idiosyncratic mind. This kind of control with supply or signal lines that are required to make or break. On the body in a number of control buttons are. Often a different color to indicate the purpose of or are labeled. Separate exclude mutual pressing, not to a hardware failure occurred.
Sometimes the button, depending on the position closes and opens the circuit at the same time two different turn. Both can not be connected, only one at a time. Therefore, the main characteristic of the push-button station is considered its switching capacity. Stations are recruited from the individual buttons.
of the circuit
Ordinary start and stop
The figure shows an example of the push-button station circuitry. The network turns the breaker switch P, then three phases are supplied to the magnetic actuator contacts. Circuiting the Start button to power up the relay, at the same time turns on normally torn contact K. Through magnetic contactor will now receive food. Contact force K is held electric coil windings.
Stop button at the initial moment is closed, so as not to interfere with the normal diet of the magnetic starter. If necessary, turn off the engine operator presses here and block the coil supply chain contact K. Which leads to the cessation of energy supplies to the electromagnetic system. All phases are broken, the equipment finishes its work.
It will be seen that the push position can be controlled emergency stop of the engine or used to save the resource master switch. The fuses are on the case, if the operator does not have time to react, and a magnetic starter zalipnet (contact welding arc, etc.). The safety equipment is not guaranteed, the fuse is triggered with a guaranteed delay.
In modern circuits breakers are used more often. They easily withstand inrush current, but an abnormal situation immediately triggers. Known deferred mode when the current exceeds the nominal 10-50%. Operating speed depends on the difference existing between the current and working.
A side effect is protection against undervoltage. If the network sags, special provisions for the situation are not taken, at some value of the contact coil to fall, opening the circuit. Equipment shutdown occurs. Reclosing is possible only when you press the Start button.
Scheme acceleration induction motor shaft
Actually a little post here participate. But switching scheme differs from the previous one, therefore, worth considering. The idea: standing shaft easier to disperse a lower voltage. This reduces inrush currents and ensures gentle treatment. Therefore, the ideal star connection. The voltage across the winding turns are not linear, and phase - in place 380 out of 220.
If so leave after start, the power will decrease approximately to the root of three times. Required as the shaft acceleration, circuit switched to a triangle. The windings will be under the line voltage, and operation close to the maximum. To solve the problem, is generally used, the centrifugal speed or time relay sensor. The methods work best depending on the situation.
The figure shows a diagram of a time switch. As planned by said second acceleration blocks simultaneous switching contactors schemes stars and triangle, which would lead to an immediate short circuit in phases. Circuit operation:
- At the initial time the Stop button is already closed, pressed Start.
- The action closes the power supply circuit of the coil contact K.
- As a result, on the normally closed through the relay circuit power contactors stars three phases come on the engine.
- Val starts to accelerate, and the time relay in seconds.
- After reaching a certain specified period, the contacts are moved on the power switch of the triangle pattern. At this point, the motor voltage is temporarily lost, but the shaft is already rotating by inertia.
- Short circuit triangle abruptly raises the voltage to the linear induction motor, while increasing the current consumption goes to mode.
As in the previous case, pressing the Stop button interrupts the supply chain for all relays. Driving off immediately. Similarly, there is protection against sagging voltage: power to the coil contact K falls and breaks the circuit contactors triangle diagram. Star does not work, he participated only in the dispersal.
The inrush current can be reduced, and the inclusion of additional resistors on all phases. The circuit does not differ from that given above. At the initial time is reduced due to voltage division between the winding resistance and series resistor. Then the countdown begins. When a preset time has gone out, the resistor circuit is shorted contactor parallel connection, the windings are subject to full line voltage network 380 V.
A significant advantage is the reduction surges and loyal requirements for protection of machines (more sensitive class). The bottom line is this. There are classes of automata, individual approach in sensitivity, but have very low tolerances on a short-term exceeding the nominal value of the current. Therefore, reducing this value will satisfy the requirements of the protection of failure at the start and at the same time to get excellent performance, after shaft acceleration.
The difference between this scheme by switching from star to delta is that there is no need to bypass the normally closed contact. The two parallel branches are inserted into one point. We should also add that at the initial time should not load the shaft. Then launch will take place as smoothly as possible.
Conveniently displayed on the mode and asynchronous motors with slip-ring motors. In this case, the regulated sliding rheostats than achieve desired characteristics of shaft rotation. Resistance levels are no longer two, but more. The scheme is complicated, but the position remains the same button. This illustrates the versatility of its application in certain situations.
The example uses three steps starting resistances. At the initial moment after pressing the Start all work on the push-button stations, which significantly reduces the induction currents in the rotor flux linkage is weakened, and the shaft grows very slowly. But it drops sharply and power consumption, which naturally reduces the inrush current.
speed sensor or timer relays monitor the overclocking process. Once the condition is reached, the first stage of the rheostat short-circuited through the contactor. shaft speed begins to increase at the expense of the gain of the rotor and the stator flux linkage that due to the lower resistance to the induced eddy currents. At the same time the relay is activated the next time (or encoder) which continues tracking.
The process is repeated, and the stage is shorted №2, after which the engine speed is increased again. But in the case enters the last relay. At the end of his work in the rheostat fully bypassed and has no effect on the work process of the induction motor. Said technique allows you to smoothly build up speed and avoid sudden surges of current consumption.
The scheme comprises a single push-button post, but a pile of equipment, the principle of action which needs to be clarified. Hoist intended for transportation equipment, crates, boxes. The operator monitors the cabin filled, and then sends it to the desired floor. If necessary, push-button stations are placed at each exit. Thus, there are several control points.
It is assumed that the circuit breakers 1P and 2P included. Otherwise, the circuit is de-energized. Floor switches signal EP scheme cabin is above or below the level of installation of this important circuit element. Three stable positions:
- Both contacts open - the elevator is located on this floor. The figure is stuck on the second cabin.
- The only contact is closed - no cabins on this floor.
Pressing any button causes the relay of the floor ER closes a normally open contact. Therethrough energized locking control relay (SW), pushbutton tripping position by a power source. Simultaneously, the forward stroke of the engine is turned on, and the brake (TM) is released. Upon reaching the predetermined level of the two lift floors switch contact opens, depriving relays (ER) power. Contact opens, including brake, extinguishing the engine speed and energizing the push position. System ready to receive new commands.
Of course, to unload the groups of personnel necessary to provide the switch, blocking the progress of the elevator. Sometimes the remote supplied with the button "busy", which signals to all participants on the need to delay the process. Without all these measures are quite possible casualties. This sketch shows that the conventional push-button position may perform quite artful manipulations. At the same time organized layout allows you to comfortably set commands. Often push the post hangs in the supply cable and can be moved to wherever it is needed the operator, allowing the flexibility to adjust their actions under the process.
During the return stroke reversal circuit is activated. The procedure for filing a phase change in the motor winding. For the rest, the reverse is performed as a direct course.
Special button posts
Before 1 January 2016 to push-button stations covered by the GOST 30011.5.1. Since that date, should be guided by the Standard IEC 60947-5-1. Information taken from the ICS-10-2015. There are also some other documents. Standards play a role in the case where the application of special conditions. For example, explosion-proof push-button stations inside filled with transformer oil to lock arcing on switch contacts.
For switching, a special wire insulation which is resistant to the action of corrosive media. In this case, refers to oil and gasoline. Rubber insulation should be avoided throughout the aggressive plot. All live parts are immersed in oil. It follows directly that the steady insulation must also be below the liquid level.
According to international standards, explosive mixtures are divided into groups and categories. Conflict of standards in this area is small. Sign of explosion protection is placed, as a rule, on the body. This is either cast tesnonnye marks or label. Then follows a group or category of explosive mixture.
The buttons are located inside the casing and controlled by the special external elements - for example, staples. The cable is inserted through the sleeve on displacement contacts. The housing is made of high-strength materials, composite extruded mixtures are sometimes used iron, steel. button can often be in a sealed compartment, and electrical connections to the other. Simplifying security measures concerning the operation and installation of the product. Labeling provides information about the protection of IP class housing, placement category according to GOST 15150.