Based on the configuration of the main contact circuits, contactors are classified into: DC contactors and AC contactors.
Based on the operating mechanism, they are classified into: electromagnetic contactors and permanent magnet contactors.
A permanent magnet AC contactor is a type of low-power-consumption contactor that utilizes the principle of repulsion between like magnetic poles, replacing the traditional electromagnetic drive mechanism with a permanent magnet drive mechanism. Mature domestic product models include: CJ20J, NSFC1, NSFC2, NSFC3, NSFC4, NSFC5, NSFC12, NSFC19, CJ40J, and NSFMR.
DC Contactors
Development Status of DC Contactors (Domestic and International)
The overall development trend for contactors is moving toward longer electrical lifetimes, higher reliability, multi-functionality, eco-friendliness, a wider range of specifications, intelligence, and communication capabilities.
Hybrid DC Contactors
Compared to AC current, DC current does not exhibit periodic zero-crossing points. Consequently, when traditional contactors interrupt a circuit, the electric arc generated between the contacts is significantly more intense, and the arcing duration is longer, as this is necessary to fully dissipate the residual energy within the circuit. The combustion of the arc generates high temperatures and intense light, resulting in severe ablation of the contact surfaces. Over numerous switching cycles, the contact material gradually erodes; when this electrical wear becomes severe, it renders the DC contactor unserviceable, preventing it from effectively interrupting the circuit.
With the rapid advancement of power electronics technology, power electronic components have been integrated into DC contactors. This ingenious application has led to the creation of the hybrid DC contactor, marking a significant step forward in making DC contactors more intelligent and controllable. This hybrid contactor leverages the inherent advantages of traditional DC contactors-specifically their low contact resistance and minimal voltage drop during the closed (conducting) state-by connecting a contactless switch in parallel across the traditional contactor's contacts. This contactless power electronic switch, which consists of anti-parallel thyristors and a control module unit, generates no electric arc when interrupting the circuit. This effectively eliminates the electrical wear on the contact material caused by arcing in traditional contactors, thereby substantially extending the service life and enhancing the reliability of the contacts.
Permanent Magnet Mechanism for DC Contactors
As one of the most widely used types of electrical switches, DC contactors are produced and demanded in vast quantities. During normal operation, the electromagnetic coil remains continuously energized to generate electromagnetic attraction, ensuring the core and armature remain engaged; this action drives the moving and stationary contacts to close, thereby completing the electrical circuit. In this process, the coil's inherent electrical resistance leads to a continuous consumption of electrical energy. This energy consumption constitutes one of the primary operating costs associated with DC contactors, resulting in significant waste of both energy and financial resources. Consequently, identifying methods to reduce the operational energy consumption of DC contactors stands as a critical and challenging focal point in the field of DC contactor research. The permanent magnet operating mechanism for DC contactors represents an evolutionary advancement built upon traditional electromagnetic operating mechanisms. It functions as a hybrid mechanism that integrates both electromagnetic actuation and permanent magnets. Rather than relying solely on the conventional electromagnetic attraction and spring counter-force to drive the engagement and disengagement of the core, this mechanism incorporates the attractive force of permanent magnets acting upon the core. Furthermore, it utilizes the charging and discharging of energy-storage capacitors to provide the requisite power for closing and opening operations-a methodology commonly characterized as "electromagnetic actuation, permanent magnet holding, and electronic control." During the opening and closing transitions, the electromagnetic attraction, permanent magnet attraction, and spring forces act in concert; however, during steady-state operation, the permanent magnet attraction supplants the electromagnetic attraction to maintain the engaged state between the armature and the core. This approach offers several distinct advantages: First, the permanent magnet operating mechanism achieves substantial energy savings by eliminating the continuous power consumption typically required to energize the holding coil, thereby promoting environmental protection and energy efficiency. Second, utilizing permanent magnets to maintain the engaged state-as opposed to electromagnetic holding-results in lower noise levels and zero environmental pollution. Third, the permanent magnet operating mechanism eliminates the series of complex and cumbersome mechanical latching and protection devices typically found in purely electromagnetic mechanisms; this significantly enhances the operational reliability of the contactor's operating mechanism, streamlines manufacturing processes, reduces production costs, and ultimately allows for a more compact contactor design.
