Modular Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), and they are used in power generation, distribution, and utilization scenarios. In a broad sense, contactors refer to electrical devices used in industrial electricity, where a coil carries current to create a magnetic field, closing the contacts to control electrical loads.

Before installing AC contactors, it is essential to understand the installation and usage guidelines. A clear understanding of these guidelines is crucial for the smooth progress of subsequent work. The primary considerations are the normal operating conditions and installation requirements for AC contactors.

Let’s first get acquainted with the product and then delve into the normal operating conditions and installation requirements for AC contactors.

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What is AC Contactor ?

ONCCY AC contactors (referred to as contactors below) are primarily designed for use in AC circuits with a frequency of 50Hz or 60Hz, with rated operating voltages up to 1000V and rated operating currents up to 800A. They are used for remote circuit connection and disconnection and can be combined with appropriate thermal overload relays to create electromagnetic starters, providing protection against potential circuit overload.

Normal Operating Conditions and Installation Requirements for AC Contactors

Ambient air temperature: -5°C to +40°C. The average temperature within 24 hours should not exceed +35°C.

Altitude: Not exceeding 2000m.

Atmospheric conditions: When the maximum temperature is +40°C, the relative humidity of the air should not exceed 50%. Higher relative humidity is permissible at lower temperatures, such as 90% at 20°C. Special measures should be taken to address condensation resulting from temperature variations.

Pollution degree: 3.

Installation category: Category III.

Installation conditions: The inclination of the installation surface to the vertical plane should not exceed ±5°.

Shock and vibration: The product should be installed and used in places with no significant shaking, impact, or vibration.

AC Contactor Model Specifications

AC contactors come in various models. In practical applications, different models represent the same parameter values and are suited for different working conditions and applications. To make informed choices regarding selection, installation, and maintenance based on the requirements of electrical equipment, it is essential to familiarize oneself with the main models and technical parameters of contactors. Therefore, I present the AC contactor model specifications for your reference.

Main Specifications of AC Contactors

Classified by current rating: 115A, 150A, 185A, 225A, 265A, 330A, 400A, 500A, 630A, 800A.

Classified by rated control power supply voltage (Us) for the contactor coil: AC 50Hz or 60Hz, AC 110V (115V), AC 220V (230V), AC 380V (400V); DC 110V, DC 220V.

Please refer to Table 1 for the main parameters and technical performance indicators of AC contactor model specifications.

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The Role of AC Contactors

AC contactors are widely used for the interruption and control of electrical circuits. They employ main contacts to open and close circuits and auxiliary contacts to execute control commands. Main contacts generally have normally open contacts, while auxiliary contacts often include two pairs of normally open and normally closed contacts. Small-sized contactors are frequently used as intermediate relays in conjunction with the main circuit, enabling remote control or weak electrical control of strong currents.

The contacts in AC contactors are made of silver-tungsten alloy, offering excellent conductivity and high-temperature resistance.

AC contactors can be further classified into permanent magnet AC contactors and electromagnetic AC contactors.

The actuation mechanism of AC contactors is driven by an AC electromagnet. This electromagnet is composed of two “shaped” silicon steel sheets, one of which is fixed and fitted with a coil. There are multiple choices for the operating voltage. To ensure stable magnetic force, a short-circuit ring is added to the pole faces of the iron core. After a power loss, AC contactors rely on springs for reset. The other half is the movable iron core, which has the same structure as the fixed iron core and is used to open and close the main contacts and auxiliary contacts.

Permanent magnet contactors replace traditional electromagnetic actuators with a novel, low-power consumption actuation mechanism. Their working principle relies on the repulsion of like poles and attraction of opposite poles. The polarity of the permanent magnet on the interlocking mechanism of the contactor remains constant, while the soft iron fixed on the contactor base, under the influence of an external control signal, generates pulses of current lasting from ten to twenty milliseconds, resulting in changes in polarity, which allows the main contacts of the contactor to attract, hold, or release.

Permanent magnet contactors offer several advantages: (1) High reliability, unaffected by variations in power supply voltage. (2) Fast response, with a time of 0.12-0.15 seconds compared to the traditional 0.35-0.38 seconds. (3) Quiet operation, no AC noise, and impervious to dust and oil. (4) Minimal temperature rise in modules and resistance to aging, with a usage life three times that of traditional contactors. (5) Low maintenance and energy-saving protection.

Contactors rated above 20 amperes are equipped with arc extinguishing covers, which use the electromagnetic force generated when the circuit is interrupted to quickly extinguish the arc and protect the contacts.

Although the design and performance of AC contactors have continued to improve, their fundamental function remains unchanged. Regardless of how advanced technology becomes, AC contactors maintain their vital role.