What Is an ATS Automatic Transfer Switch? Why Diesel Generators Need ATS

When utility power fails, a diesel generator provides backup power, while an ATS (Automatic Transfer Switch) automatically transfers the load between utility and generator power.

ATS systems are widely used in hospitals, data centers, factories, telecom sites and commercial buildings that require automatic standby power.

Voltgent provides complete diesel generator + ATS solutions for different project requirements.

What Is an ATS Automatic Transfer Switch?

ATS stands for Automatic Transfer Switch.

It automatically switches the load between:

● Utility power

● Diesel generator power

Utility fails → Generator starts → ATS transfers the load → Utility returns → ATS switches back

The entire process can operate automatically without manual switching.

Main Components of an ATS System

An ATS system normally includes several important components.

The exact design depends on generator capacity, voltage, current, application and project requirements.

How Does an ATS Work with a Diesel Generator?

The ATS automatically manages the transfer between utility and generator power:

1.  Monitors utility power

2.  Detects mains failure

3.  Starts the generator

4.  Transfers the load to generator power

5.  Monitors utility recovery

6.  Transfers the load back and stops the generator after cooling

The complete process is automatic and controlled by the ATS or AMF system.

Why Is ATS Important for a Diesel Generator?

A diesel generator can operate without an ATS, but manual starting and load switching may be required.

With ATS, the system can automatically:

● Detect power failure

● Start the generator

● Transfer the load

● Return to utility power

● Reduce manual operation

● Improve backup power response

ATS is therefore especially suitable for automatic standby and unattended power systems.

Does ATS Provide Uninterrupted Power?

No. A standard ATS + diesel generator system usually has a 10–30 second power interruption while the generator starts and stabilizes.

For critical loads requiring continuous power, a UPS is normally used together with the generator and ATS.

ATS vs AMF: What Is the Difference?

ATS transfers the electrical load between utility and generator power.

AMF detects mains failure and automatically starts or stops the generator.

In many modern generator controllers, the AMF function is already integrated.

Types of ATS Automatic Transfer Switches

Common ATS types include:

● PC Class ATS – Mainly used for power source transfer.

● CB Class ATS – Combines transfer switching with circuit protection.

● Contactor Type ATS – Compact and cost-effective for smaller systems.

ATS selection should consider generator capacity, current, voltage, poles, short-circuit rating and application requirements.

Voltgent ATS Solutions

Voltgent offers flexible ATS integration based on generator size and project requirements.

1. Built-In ATS

Compact ATS integration for small standby generator systems.

2. Integrated ATS Cabinet

Suitable for medium-capacity generators, combining easy installation with a compact design.

3. Separate ATS Cabinet

Recommended for larger generators, providing more space for switching, protection, cabling and maintenance.

For industrial projects, Voltgent can also design customized ATS and control systems based on the single-line diagram and load requirements.

Typical ATS Applications

ATS systems are widely used where automatic backup power is required, including:

● Hospitals

● Data centers

● Industrial facilities

● Telecom sites

● Commercial buildings

● Airports and railways

● Water treatment plants

● Mining and oil & gas projects

For critical loads, ATS can also work with UPS and other emergency power systems.

How to Select the Correct ATS Size

ATS selection should consider more than generator kVA.

Key factors include:

● Rated current

● System voltage: 220V–480V

● Number of poles: 3-pole or 4-pole

● Short-circuit rating

● Application requirements

The correct ATS should match the generator, load and site electrical system.

ATS for Single and Multiple Generator Systems

ATS can be used in both simple and complex power systems, including:

● Utility + one generator

● Utility + multiple generators

● Dual utility + generator

● Generator paralleling systems

For multiple generators, ATS may work with synchronizing controllers, paralleling switchgear and load-sharing systems.

FAQ About ATS for Diesel Generators

Q1: What is the difference between ATS and AMF?

ATS transfers the load between utility and generator power, while AMF monitors mains power and controls generator start/stop.

Q2: Does every diesel generator need an ATS?

No, ATS is mainly recommended for automatic standby systems that require unattended power transfer.

Q3: How long does an ATS take to restore generator power?

Generator power is typically restored within 10–30 seconds, depending on generator starting and controller settings.

Q4: Can utility power and generator power be connected at the same time?

Normally no, unless a specially designed closed-transition or paralleling system is used.

Q5: Can ATS be used with different types of diesel generators?

Yes, ATS can be used with standby, prime, silent, containerized and industrial generator systems.

Q6: Can Voltgent provide a complete ATS solution?

Yes, Voltgent provides complete ATS, AMF, control, protection, monitoring and paralleling solutions for generator projects.

Need a Diesel Generator with ATS?

Voltgent provides complete diesel generator + ATS solutions for standby and emergency power projects.

Tell us your generator capacity, voltage and application, and we’ll help you select the right ATS and control system.

Contact Voltgent for a customized generator + ATS solution.