The Parameters and Functions of Automatic Transfer switches

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1. The utilization category of automatic  transfer switch


To understand the use of dual power automatic transfer switch utilization category, the first step is to find out the nature of the current used by the dual power automatic transfer switch. The current nature of the dual power transfer switch is AC. The operation category can be divided into OPERATION A and  OPERATION B, which are summarized in a table as follows.


Utilization Category

 Typical Applications

A Operation

B Operation



AC-31 B

Noninductive or weak inductive load



Mixed load, including moderate load



The total system load includes cage motor and resistive load



Motor load or containing motor resistance load and mixed load of incandescent lamp load Under 30 percent

AC-35 A

AC-35 B

Discharge lamp load

AC-36 A

AC-36 B

Incandescent lamp load


Here’s an explanation: what each letter stands for?

ATS Utilization Category

These parameters directly determine the load switching capability of ATSE, Due to the limitation of ontology switch’s own functional structure, derived ATSE cannot meet the A operation category (The rated current of the specified multiple frequently switches 50 times).


2. ATSE Rated limit short circuit current (Inc)

Rated limit short circuit current: Iq value: Short circuit protection appliance is placed in front, After the protection device breaks off the current,ATSE can still normal electricity and transformation ,the rated limit short-circuit current (Iq) can reach 120kA if the fuse is in front.


3. Transfer time

ATSE switching time consists of two parts: Logic judgment time, determined by controller performance;Body switching time, from one power supply is completely disconnected until the other power supply is closed.

The dedicated PC-class ATSE conversion time of the exciter set driving motor  is 50ms-300ms

Motor driven load isolation switch derived PC-class ATSE is 700 ms to 1.5 s

Motor driven CB class ATSE is 1.5s-3S

ATSE conversion time how fast the choice depends on the load demand for electricity (load allowed in the action time of power), and whether there is a multi-stage ATSE system design.

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