A. Magnetic Contactor
Magnets or magnetic contactor switches are switches that work based on magnetism. This means that these switches work when there is magnetic force. Magnets function as towing and release contacts. A contactor must be able to stream flow and decide the current in normal working condition. Normal operating current is current flowing during the disconnection does not occur. A magnetic contactor coil (coil) can be designed for direct current (DC) or alternating current (AC). AC contactor is mounted on ring core magnetic short circuit, the point is to maintain a continuous flow of magnetism for so that the contactor is able to work normally. While on a magnetic coil that is designed for DC current short circuit ring is not installed.
Working Principle
A contactor consists of a coil, some of the contact Normally Open (NO) and several Normally Close (NC) At the time of a normal contactor, NO will open and when the contactors work, NO will close. While the NC contacts the opposite of when in normal circumstances the NC contacts will close and NC contacts in working condition will be opened. Coil is a coil which, when given the stress will occur magnetization and interesting contacts so that there is a change or work. Electromagnetic contactor operated is one of the most useful mechanism ever designed for closing and opening the electrical circuit is drawing the working principle of a magnetic contactor can be seen in the following figure:
Magnetic contactor specifications that must be considered is the ability of the contactor was written in the size of Watts / KW, which is adapted to bear loads, the ability to deliver current from the contacts - contacts, written in units of amperes, voltage capability of magnetic coils, whether for voltage 127 or 220 Volt Volt, as well as the frequency, the ability to protect against low voltage, for example written ± 20% of the working voltage. Thus in terms of safety and practicality, the use of a magnetic contactor is much better than regular switches.Applications
The advantages of using the magnetic contactor as replacement equipment which is operated manually control include:a. In handling large currents or high voltages, it is difficult to construct manually a suitable tool. Moreover, such a device is large and difficult to operate. On the contrary, will be relatively simple to build a magnetic contactor which will handle large currents or high voltages, and the manual device should control only the coil of the contactor.
b. Contactor enable multiple operations carried out from one carrier (one location) and diinterlocked to prevent errors and operating hazards.
c. Operation should be repeated several times in an hour, can be used contactors to save the business. Operators simply need to press buttons and contactor sequence of events that will start automatically.
d. Contactor can be controlled automatically by means of a pilot or a highly sensitive sensors.
e. High voltage can be overcome by the contactor and away entirely from the operator, thereby increasing the safety / security installation.
f. By using a contactor control equipment can be fitted at points distant. The only space is needed near the engine room for the button press.
g. With contactor, automatic and semi automatic control may be done with equipment such as a programmable logic control such as Programmable Logic Controller (PLC).
1. Contactor Magnet Direct Current (DC)Contactor magnet direct current (DC) consists of a coil that is essentially made of iron. So when an electric current flowing through the coil, the iron core will become a magnet. Magnetic force is used to attract the armature is at once close / open contacts. When electric current is lost to the coil, the magnetic force will be gone and spring will withdraw / reject the armature so that the contacts re-open or close.To design a large direct current contactors required greater work stress, but this will result in current through the coil will be large and will quickly heat contactors. So the direct current magnetic contactor will be efficient on the working voltage as small as 6 V, 12 V and 24 V.
Figure 1. Symbols and physical images DC magnetic contactor
Physical form of relay is packed with transparent plastic container, having two contacts SPDT (Single Pole Double Throgh) Figure 2.1, one main contact and two branch contacts.) Relays of this type using a 6V DC voltage, 12 V, 24 V, and 48 V. Also available with voltage AC 220 V. The ability of the contact a current of electricity is limited to less than 5 amperes. To be able to stream large power flows to control induction motors, relays associated with
When direct current contactor for use on AC current then kemagnetannya will arise and disappear at any time following the wave of AC current.
1. Contactor Magnet Alternating Current (AC)
Construction magnetic contactor ac contactor is basically the same as magnet direct current. However, due to the nature of alternating current sinusoid waveform, then at one period there were two major voltage equal to zero. If the frequency of AC current 50 Herz will mean in 1 second contains 50 waves. And 1 period will take 1 / 50 = 0.02 seconds which took two times zero. Thus in 1 second occurs 100 times a zero point or within 1 second magnetic coil magnets lose 100 times.
Figure 2. Symbols and code numbers, and physical form of contactor
Therefore, to fill the loss of magnets on the magnet coils due to loss of flow then made winding short circuit that functions as a generator when the current magnetic induction of magnets on a magnetic coil missing. Thus, the magnetic currents on the contactor will be maintained continuously (continuous).
When contactors are designed for use on AC current, the DC current in the coil does not arise so that the electric induction coil to heat. Sebaliknnya, if the magnetic contactor for DC current that has no windings short circuit the AC current supplied to the contactor it will vibrate due to the magnetism in the magnetic coil arise and disappear every 100 times.
Contactor will work normally when the voltage reaches 85% of the working voltage, when the voltage drop contactor will vibrate.
The size of the contactor is determined by the current limits. Usually there are some contacts on the contactor, which is normally open contacts (Normally Open = NO) and normally closed contacts (NC = Normally Close). Contact No mean when a magnetic contactor is not working position when the contactor opens and closes the contacts working / connecting. While the NC contact means when the contactor is not working position when the contactor contacts closed and the work that contact open. So the work function of NO and NC contacts opposite. NO and NC contacts to work more quickly to open shortly before the NO contacts close.
Figure 3. Symbols magnetic contactor. a) coil (coil), b) Main Contact, c) auxiliary contacts
The function of the contacts made to the main contacts and auxiliary contacts. The main contacts consist of NO contacts and auxiliary contacts consist of NO and NC contacts. The main contacts are used to drain the mainstream, namely the required current to power the user plane for example electric motors, aircraft heating and so forth. While the auxiliary contacts are used to aid the flow stream flows necessary for the magnet coils, alt auxiliary circuit, indicator lights, and others.
From the information above can be seen that the advantage of using magnetic contactors and switches instead of toggle switches Cam is,
* An electric current flowing in the switch controller is very small compared to the load current.
* Can control the electrical load from a distance with a relatively small voltage loss.