What Are The Two Types Of Automatic Transfer Switches?

Automatic transfer switches classified according to its structural design and functional characteristics. The two most common types are PC (Integrated) ATS and (integrated) ATS and CB (circuit breaker) ATS. Here's a closer look:
1.PC-class ATS (Integrated)
Structural features:
A single mechanical structure,such as a load switch or disconnect, is used to switch between two power sources.
It has no internal overflow release, only the ability to connect and carry currents without interrupting short-circuit currents.
It is usually a integral design, a contact system independent of the protective device, making switching more straightforward.
Operational principles:
Using an electromagnetic or motor driven mechanism, it quickly switches to a backup power source in the event of a main power failure.
Switching time is short (usually ≤ 0.1 seconds) and therefore suitable for applications requiring high power continuity.
Applicable Applications:
Low load currents and rare applications such as small commercial buildings and residential areas.
Work with downstream protectors (such as fuses and circuit breakers) that interrupt short current. Strengths:
Low cost: simple structure, no complex protection modules, low price.
High Reliability: few mechanical components, low failure rate, suitable for long-term use.
Fast switching speed: Direct mechanical switching, no intermediate link, fast response time.
Weaknesses:
Short-circuit protection: Dependence on external protection increases system complexity.
Overload capacity is limited: long-term overload can lead to contact corrosion and requires strict load current matching.
2. CB level automatic switch (Circuit Breaker Type)
Structural features:
It consists of two circuit breakers (or switches that overcurrent releases), each controlling the main power supply and backup power supply.
An integrated overcurrent release provides short-circuit and overload protection.
It is usually designed in an integral fashion, with mechanical or electrical interlocking of two circuit breakers.
Operational principles:
When the main power supply fails, first turn on the main power breaker, then switch on the backup power breaker to complete the switch.
Switching time is relatively long (generally ≥ 0.5 seconds) because faulty circuits must be disconnected first.
Applicable Scenarios:
Places with high security requirements (such as hospitals, data centers and airports).
Frequent short-circuit current interruptions are required in high-power motor or high-inductive load environments.
Strengths:
Integrated protection: independent interruption of short circuit and overload currents, reducing the need for external protection devices.
High safety: Dual circuit breaker design eliminates the risk of two power sources being connected simultaneously.
Adaptability: Supports higher current specification to meet diverse load requirements.
Weaknesses:
High costs: Complex structures require more materials and processes, leading to higher prices.
2.2. Slow switching time: Due to the need to disconnect fault circuit first, switching time is relatively long.
Complex maintenance: circuit breaker module modules require periodic inspection and are costly to maintain. Type Comparison Summary
Functional PCB rating
Structure: Single machine structure, double circuit breaker structure, no buckle element, with buckle element
Protection Function: no short circuit protection, short circuit protection, overload protection
≤ 0.1 seconds ≤ 0.1 second (fast) ≥0.5)
Cost: Low, high
Reliability: High (fewer mechanical parts) (but circuit breaker maintenance required)
Applicable Scenarios: Small load, infrequent operation, large load, high security requirements.
Selection Recommendations: If the load current is low, the switch time sensitive (such as UPS input) and the system already has comprehensive short-circuit protection (such as downstream circuit breakers), the PC level is preferred.
CB rating is preferred if the load is high current, requires independent short-circuit protection (e.g. fire pumps and elevators) or has high safety requirements (e.g. operating theatres and data centers).
Hybrid solution: In some cases, combining PC-level switches and CB level circuit breakers balances cost and security.