Dual power transfer switchgear (transfer switch ATS, also known as ATSE, is the abbreviation of Automatic transfer switching equipment.) An appliance that converts one or several load circuits from one power source to another. It consists of one (or several) switchgear and other necessary appliances for monitoring the power circuit and automatically switching one or several load circuits from one power source to another. In the electrical industry, it is simply referred to as “dual power automatic transfer switch” or “dual power switch”.

The dual power automatic switch is a device controlled by a microprocessor for switching between the network power and the grid power or the grid power and the generator power source in the power grid system, so that the power source can be continuously sourced. Series dual power supply, when the common power suddenly fails or power failure, through the dual power switch, it is automatically put into the standby power supply (the backup power supply can also be powered by the generator under small load), so that the equipment can still operate normally. The most common are elevators, fire protection, surveillance, lighting, etc.

The development of dual power switching system products has generally experienced three types: contactors, molded case circuit breakers/load disconnectors, and integrated automatic transfer switch appliances.

Contactor class

Such a power switching system uses a contactor as a switching execution component, and a switching function uses an intermediate relay or a logic control module to form a secondary loop to complete a control function, which is generally a non-standard product. The disadvantage is that the primary loop contactor requires a secondary circuit to be energized for a long time. It is prone to failures such as temperature rise and heat generation, contact bonding, and coil burnout. Because it is a non-standard product, it has many components and components. The quality of the product is restricted by components and manufacturing processes, and the failure rate is high. It has been gradually replaced by new products. [2] 

Molded case circuit breaker

This type of power switching system uses the Molded Case Circuit Breaker as the switching execution component. The switching function is completed by the ATS automatic control unit. It has mechanical and electrical interlocking functions, perfect functions, good operating performance, high service life, fewer components and components, and easy installation. . This class is a CB-class transfer switch device. It is equipped with two circuit breakers as current breaking units and equipped with a current release device. It has certain protection capability. The circuit breaker's on/off capability is much higher than that of the relay. [2] 

This type of product is maintained by the mechanical structure during steady state. Due to the difference between the circuit breaker and the load isolation switch itself, the application effect under the overcurrent condition is not as good as that of the PC grade product.

Load isolation switch

The load isolating switch type transfer switch device is assembled by assembling an electric operating mechanism, a mechanical interlocking mechanism and an automatic control unit on the basis of two load isolating switches. The breaking unit of the current is a load isolating switch, and the contact arc extinguishing system is designed to break the primary arc requirement, and does not have the protection function of the circuit. This kind of product belongs to the PC grade product, and it adopts spring energy storage and instantaneous release. The acceleration mechanism can quickly turn on, break the circuit or perform circuit conversion, and the product operation performance is reliable.

Integrated automatic transfer switch

This kind of power conversion system is a combination of switch and logic control, which does not require an external controller, and realizes the electromechanical integration of the automatic transfer switch. The contact system of this kind of power switching system product adopts the "single-pole double-throw" design, which is designed and manufactured uniformly, small in size and simple in structure. This product does not have current protection function and belongs to PC level conversion switch electrical products. The general conversion time of this kind of products is relatively small, the switch switching drive adopts motor drive, the switching is stable and reliable, the motor drive of the operator only has current flowing at the moment of switching, and the operating current is not required in steady state, and the energy saving is remarkable. The product has no heating, heating, contact bonding, and coil burning. The switch has an electromechanical interlocking device, which can realize self-returning self-recovery, self-injection, self-recovery, voltage loss, undervoltage, phase failure protection, manual-automatic conversion, delay control, etc., and is a mainstream product of power switching.

ATS is suitable for dual power supply with key loads such as fire protection in the construction field. EPS is suitable for EPS. It is mainly aimed at solving primary load power supply equipment such as emergency lighting, accident lighting and fire protection facilities, and provides an independent fire protection code. Emergency power supply system for the circuit. UPS is mainly used to provide electricity for IT industry equipment, providing a clean, uninterrupted backup power supply. The diesel generator power supply mode is suitable for use in conjunction with ATS, EPS, and UPS in power supply locations where long-term backup power is required.