Being able to maintain power continuity is essential in current-day systems such as hospitals, data centers, and factories, which depend on the availability of backup power that is triggered by the Automatic Transfer Switches (ATS). Huyu Electric produces ATS solutions for reliable source switching, with PC-Class and CB-Class types serving different needs. This article explains how Huyu Electric ATS works, the differences between PC-Class and CB-Class, and suitable applications.
The Role of an Automatic Transfer Switch
A transfer switch automatically monitors the utility power source and activates backup power, like a generator, when voltage drops or power is cut off. Once power stabilizes, it transfers the load back to one. When the normal source returns and stabilizes, the ATS switches the load back. In intelligent power distribution systems, the ATS does more than mechanical switching. Modern designs include controller logic, sensing circuits, and communication interfaces that allow status reporting, remote commands, and event logging. Huyu Electric integrates these functions into its ATS range to support both standalone and networked installations. The main technical division in ATS products is between PC-Class and CB-Class designs.
What Is a PC-Class Automatic Transfer Switch
PC-Class stands for power switching class. A PC-Class ATS is built primarily as a switching device rather than a protective device. Its main function is to swiftly transfer load between two power sources under normal and abnormal conditions. Upstream or downstream circuit breakers manage overloads and short circuits, not the ATS. Huyu Electric PC-Class ATS units use a load break switch or contact assembly with mechanical and electrical interlocks, preventing simultaneous connection of both sources. Transition can be open with a brief interruption or closed with a brief overlap. PC-Class ATS units, designed for switching duty, offer high mechanical endurance and quick transfer times. They’re ideal for frequent switching, like testing generators or improving utility quality that fluctuates.
What Is a CB-Class Automatic Transfer Switch
CB-Class stands for circuit breaker class. In this design, the ATS is built using two interlocked circuit breakers, each connected to a different power source. The breakers perform both the switching and the protection functions. All the breakers are equipped with trip units and protection settings. The mechanism of interlocking makes sure that the breaker may be closed only once, so that there is no back feed between sources. The difference between these structures influences size, weight and wiring. The ATS offers built-in overcurrent protection due to circuit breakers. CB-Class ATS designs are common for coordination with protective devices or code-based breaker isolation.
Structural Differences Between PC-Class and CB-Class
The most visible difference lies in the internal hardware. A Huyu Electric PC-Class ATS uses a dedicated switching assembly. It does not have thermal or magnetic trip units inside the switch. Its current-carrying parts are sized for load duty and short-time withstand, but it relies on external breakers to clear faults. In contrast, a Huyu Electric CB-Class ATS contains two full circuit breakers. Each breaker has its own trip unit and protection settings. The interlocking mechanism ensures only one can close at a time, preventing back feed between sources. This structural difference affects size, weight, and wiring. PC-Class ATS units are often more compact for the same current rating. CB-Class units are larger because they house two breakers and associated mechanisms.
Functional Differences in Operation
In a PC-Class ATS, when a fault occurs on the load side, upstream protective devices operate. The ATS itself does not trip on overload. Its role is to maintain the connection to whichever source is healthy and available. This separation of switching and protection simplifies coordination because dedicated breakers handle the protection scheme. In a CB-Class ATS, the breakers can trip on overload or short circuit. This means the ATS becomes part of the protection hierarchy. Coordination studies must consider the trip curves of the breakers inside the ATS, along with other system breakers. Transfer speed can also differ. PC-Class switches are designed specifically for rapid transfer and often achieve shorter switching times. CB-Class designs involve mechanical breaker operation, which may be slightly slower but still within acceptable limits for most applications.
Application Scenarios for PC-Class ATS
Huyu Electric PC-Class ATS units are commonly used in applications where frequent switching is expected and where protection is already well defined elsewhere in the system. Data centers are a typical example. They usually have upstream main breakers and downstream branch protection, so the ATS only needs to switch between utility and generator or between two utility feeds. Commercial buildings with standby generators also benefit from PC-Class ATS. The focus is on reliable transfer and long mechanical life. Because these systems often undergo routine generator testing, the durability of the switching mechanism is important. Industrial facilities with stable protection coordination also use PC-Class ATS when the goal is to minimize downtime during source changes while keeping the protection scheme centralized in the main switchgear.
Application Scenarios for CB-Class ATS
Huyu Electric CB-Class ATS units are often selected where integrated protection and switching are preferred in one assembly. Small to medium facilities may use CB-Class ATS at the service entrance or main distribution point to combine functions and reduce the number of separate devices. Projects that must meet specific regulatory requirements for breaker isolation sometimes favor CB-Class designs. Each source connects through a circuit breaker, offering clear isolation and visible trip status. In systems with tight fault level and coordination control, engineers may select CB-Class ATS to finely tune transfer protection.
Considerations for Selection
The factors that need to be considered when selecting PC-Class versus CB-Class Huyu Electric ATS are the protection philosophy of the system, space, frequency of switching and coordination. If the design philosophy separates protection and switching clearly, PC-Class is often more straightforward. If combining protection and transfer in one unit is preferred, CB-Class may be the better fit. Engineers must also consider short circuit ratings, transition type, control features, and communication needs. Huyu Electric provides controller options with display interfaces, remote signals, and network connectivity, allowing both PC-Class and CB-Class ATS units to fit into intelligent power monitoring systems.
Conclusion
Automatic transfer switches are central to reliable backup power design. The difference between PC-Class and CB-Class is not just a technical label but a reflection of how switching and protection responsibilities are arranged in the system. Huyu Electric offers both types to match different engineering approaches. PC-Class ATS units focus on fast, durable switching with protection handled by separate breakers. CB-Class ATS units combine breaker protection and transfer functions in one assembly. Through the knowledge of these differences, designers and facility managers can then choose a Huyu Electric solution that would match their system architecture, safety requirements, and operational needs.
