A 63A backup circuit and a 4000A distribution system need different automatic transfer switches.
But even at the same current rating, there may be more than one suitable ATS types. The choice also depends on the drive mechanism, switching positions and how protection is arranged in the system.
At AISIKAI, our SKT1, ASKQ6, ASKQ8, ASKQ1 and SKQ1 series cover motorized, solenoid-operated and circuit-breaker-based transfer designs. This guide explains where each series fits and how to narrow the options for your panel or generator backup project.
Series | Current range | Class and mechanism | Selection starting point |
|---|---|---|---|
SKT1 | 10–3200A | PC Class; motorized | Projects requiring a motor-operated transfer switch |
ASKQ6 | 63–630A | PC Class; solenoid-operated | Solenoid transfer with a choice of two-position or three-position operation |
ASKQ8 | 630–6300A | PC Class; solenoid-operated | High-current transfer applications, including requirements above 3200A |
ASKQ1 | 6–63A | PC Class; solenoid-operated | Lower-current residential and small distribution circuits |
SKQ1 | Depends on MCB or MCCB configuration | CB Class; circuit-breaker-based | Projects specifying a breaker-based transfer arrangement |
The current ranges describe each series as a whole. Individual ratings, poles and frame sizes depend on the selected configuration.
Current is a useful first filter. For a 40A circuit, ASKQ1 falls within range, while SKT1 is another option if the project calls for a motorized mechanism. At 250A, both SKT1 and ASKQ6 are within range. At 4000A, ASKQ8 is the relevant PC Class series among the families covered here.
These examples narrow the product families; they do not size the switch for the load. Operating voltage, load characteristics and installation conditions remain part of the final selection.
Where current ranges overlap, the next decision is the transfer design. Choose between a motorized or solenoid-operated PC Class switch, or a CB Class arrangement if the specification calls for circuit breakers in the transfer assembly.
Our SKT1 motorized automatic transfer switch covers 10–3200A. It is a PC Class series with a motor-operated mechanism and an AC-33A utilization category. A three-position I–0–II configuration provides an OFF position between the two source positions.
SKT1 is a starting point for panel builders specifying motorized transfer across a broad range of circuit ratings. For example, a 250A project requiring a motor-operated mechanism points toward SKT1, while a project at the same current requiring solenoid operation points toward ASKQ6.
For panel integration, the frame size and terminal arrangement matter alongside the electrical rating. They determine the space needed for the switch, cable routing and connections to the rest of the assembly.
[IMAGE 2 — SKT1 installed in an actual distribution panel]
Our ASKQ6 solenoid automatic transfer switch covers 63–630A and offers two position arrangements:
J type: I–II, for two-position operation.
X type: I–0–II, with an OFF position.
The position requirement is a useful way to distinguish the two versions. If the project needs a defined OFF position as part of its transfer arrangement, the X type is the relevant option. If it specifies two-position operation, start with the J type.
For an enquiry, “ASKQ6, 250A, three-position” gives us a clearer starting point than the series and current alone. The required control sequence and controller functions complete the specification.
[IMAGE 3 — ASKQ6 J/X product comparison, labelled I–II and I–0–II]
Our ASKQ8 automatic transfer switch is a solenoid-operated PC Class series covering 630–6300A. It extends the selection into current ratings above the SKT1 range.
A 4000A or 6300A transfer requirement therefore points toward ASKQ8 among the PC Class families in this guide. Within the overlapping 630–3200A range, the required mechanism and panel arrangement help distinguish ASKQ8 from SKT1.
At these higher currents, the switch is closely tied to the cabinet design. Busbar layout, connection space, temperature rise and protective-device coordination need to be considered together. A single-line diagram and the available installation dimensions are particularly useful when developing the assembly.
Our ASKQ1 automatic transfer switch is a solenoid-operated PC Class series covering 6–63A. It is an option for lower-current backup circuits in residential and small distribution applications.
The circuit requirement matters more than the building label. A small residential circuit may fall within the ASKQ1 range, while a larger residential supply may require SKT1 or ASKQ6. The same principle applies to small commercial premises: select around the actual circuit, voltage and transfer requirements.
Our SKQ1 family offers MCB-type automatic transfer switches and MCCB-type automatic transfer switches for CB Class applications.
The main selection difference is the protection arrangement. SKQ1 uses circuit breakers in the transfer assembly, so the selected breaker's trip characteristics and breaking capacity form part of the specification. With a PC Class arrangement, suitable external protective devices provide the required circuit protection.
If the project specifies a CB Class ATS, start with SKQ1 and select the breaker configuration around the load and protection requirements. If it specifies a PC Class ATS, compare SKT1, ASKQ6, ASKQ8 and ASKQ1 by current range and mechanism.
[IMAGE 4 — SKQ1 MCB and MCCB versions side by side]
A short switching time describes only part of a generator backup sequence. After a utility failure, the system may need to detect the loss of supply, start the generator and allow its output to stabilize before transferring the load. Controller delays also affect the interruption experienced by the equipment.
This is why switching speed alone cannot establish whether a backup system meets the load's continuity requirements. Where the load cannot tolerate an interruption, the overall design may also need a UPS.
For background on the sequence, see the PNNL guide to automatic transfer switches.
[IMAGE 5 — Conceptual utility-to-generator sequence; no fixed timing values]
Once you have selected a likely series, bring the remaining requirements together in one specification:
Information | What to include |
|---|---|
Power sources | Utility–generator, utility–utility or another arrangement |
Electrical system | Operating voltage, frequency, phase configuration and required current |
Load | Load types, including significant motor loads |
Poles and neutral | Required pole count and neutral/earthing arrangement |
Transfer operation | Two or three positions, source priority, return sequence and delays |
Controls | Control supply, generator-start interface and position feedback |
Protection | Prospective short-circuit current and associated protective devices |
Installation | Temperature, altitude, available space and connection arrangement |
Supply scope | ATS component or complete assembled cabinet |
Pole count follows the system's neutral-switching requirements; 4P is not an automatic upgrade from 3P. Likewise, the controller and switch need to be specified together to deliver the required operating sequence.
For projects referencing IEC 60947-6-1 for transfer switching equipment, include the required edition and certification documents in the enquiry. Final selection uses the ratings, drawings and documentation for the exact configuration supplied.
Which AISIKAI ATS series should I consider for a 200A application?
For a 200A PC Class application, both SKT1 and ASKQ6 fall within range. SKT1 uses a motorized mechanism, while ASKQ6 uses a solenoid-operated mechanism. The choice depends on the required transfer arrangement and panel design. If the specification calls for a CB Class ATS, consider an SKQ1 MCCB configuration with suitable breaker ratings and protection characteristics.
What is the difference between two-position and three-position ATS operation?
A two-position ATS has source positions I and II. A three-position ATS adds a defined OFF position, giving an I–0–II arrangement. In the ASKQ6 series, J type provides two-position operation and X type provides three-position operation. The OFF position is distinct from the brief contact-opening interval during a transfer; any required dwell time depends on the selected switch and control arrangement.
Can AISIKAI supply a complete ATS cabinet instead of a switch only?
Yes. We supply ATS components for panel integration and complete ATS cabinets configured around project requirements. For a cabinet enquiry, include the current, voltage, power sources, enclosure requirements and cable-entry direction. A single-line diagram and details of any metering or monitoring functions help us define the assembly.
Send us your required current, system voltage, power-source arrangement and preferred series, together with a single-line diagram if available. We can then help narrow the configuration for your panel or complete ATS cabinet.
You can also find selection guides and manuals in our Download Centre.
