Mechanically held contactors have two different coils, a latching coil and an unlatching coil. Life Expectancy of Contactors. In AC applications where switching is at random, either contact may be negative or positive when arcing occurs. While technology has improved over years, the primary means of controlling electrical circuits remain the same. Mechanically held relays and contactors are often used because one. Transformers can present an unusual trap for an unsuspecting relay user. That is, when the arc is suppressed, contact temperature is held to a minimum. The stiffness of the reeds causes them to separate and open the circuit, when the magnetic field ceases.
The use of a contactor provides a level of isolation away from the high electric currents associated with those applications, protecting workers and equipment. Some examples include: AC Mechanically Interlocked - IEC. NEMA contactors are primarily used in North America however, more companies are adopting IEC contactors, c3controls specializes in IEC. How To Apply A Contactor To A Lighting Application | Sprecher + Schuh. Both perform the same task of switching a circuit! In a second known method, a single coil, which when activa ed pulls a plungert towards a center position with a follow through due to its momentum to the other side. Gold flashing on each contact results in minimal sulfidation, and provides good electrical make upon contact.
The function of the contactor is always the same; to make and break all power. A magnetic contactor is operated electromechanically without manual intervention. The contactor 10 is held in this altered state, without the control power 412 being supplied to its coil. Common applications include liquid level control, load shedding, power factor correction, and over/undertemperature monitoring. In such instances, the contacts break load current at the same approximate point on the sine wave. The contactor is electrically controlled and usually powered at a much lower level than the switched circuit. As with every electrical device, it is vital to ensure you find one that matches your needs and function. In turn, the coil/electromagnet creates a magnetic field which makes the contactor move the armature. This short-circuit style inrush is on the order of 17 times the continuous ampere draw but only lasts a few milliseconds. They have an electrical life expectancy of approximately 10 times that of fine silver contacts. Identifying mechanically held contactor versus electrically held contactor | Schneider Electric USA. 5, it can be mounted or inserted close to the contactor coil, such as near coil cover 96, and auxiliary contacts 220 so as to facilitate its connection to these for signaling purpose as will be described with respect to FIG. The main difference between soft starters and contactors is the use of an overload relay–a sensitive coil that monitors changes in ambient temperature and the amount of heat generated by excessive inrush current to the motor. With a relay there very well could be.
The excited electromagnet generates a magnetic field, which causes the core of the contactor to move the armature. Examples of applications where soft starters are used to control industrial AC motors include: centrifugal pumps, crushers and grinders, conveyor belts, fans and similar systems (i. e. blowers and exhausters), mixers and aerators, conveyor belts, and in electric helicopters. The contactor coils are generally rated for short time duration. Mechanically held relays and contactors are often used because they can. They also have an OFF state in which they limit and control the electric current supplied to the motor. 63 is the capacitor voltage loss during one time constant of 2. This flexibility is one of the main advantages of electromagnetic control over manual control. It helps reduce the eddy current loss.
The frame or enclosure. A middle limb of the magnet 52 is inserted in the hole of the bobbin 670 from one side, and the magnet along with the bobbin is fitted in the base 12, being inserted through the opening provided in the cover 70. It provides the driving force required by the contactor to close the power contacts. Material Transfer and Material Loss. But, if it travels from position 2 to position 1 due to coil energization, it goes to position 3 after de-energization of the coil. In some cases, it may even be desirable to have more than two-poles of contacts within a single contact module. BACKGROUND OF THE INVENTION. Mercury has a boiling temperature of 357oC. A first supporting arm 30 includes a first extension 34 adjacent the armature 28 and running generally alongside the first side 14. Mechanically held relays and contactors are often used because they connect. 5 and 6, the main cam 24 is held towards the side 18 against the spring bias which is trying to push it back towards the side 20. Not all AC applications incorporate random switching, however. At the position 1 or position 2, the profiles on the main cam 24 to actuate the contact modules seated upon the contactor 10 are at the same level.
Double-break contacts open the circuit in two places simultaneously. Because silver and silver alloys sulfidate, contact pressures must be great enough to break through this film. An has two basic parts: - A heater element that is connected in with the power line to the motor. In contrast, it is common practice in North America to combine tungsten and ballast applications into one group. Home | Articles | Forum | Glossary | Books|. Worst case circuit conditions dictate contact rating, not steady state conditions. A cable with a restrainer at the bottom hangs vertically from its upper end. The supply voltage to the connected motor is controlled by adjusting the firing angle of the thyristors or SCRs.
If this distance is extended further than the energy can overcome, the arc is suppressed. The arc that's formed when the contacts open can be lengthened and extinguished by motor action if it's in a magnetic field. Double break contacts divide the connection in such a way that it forms two sets of contacts.