Schneider ATS22: A Reliable Soft Starter for Efficient Motor Control

Schneider ATS22: A Reliable Soft Starter for Efficient Motor Control

30 May 2026 · 8 min read · Trans-Digi Global

The Schneider Altistart 22 (ATS22) is an all-in-one soft starter for three-phase asynchronous motors from 4 kW to 400 kW. It ramps the motor up and down with torque control and current limiting, then switches to its integrated bypass once the motor is at speed, giving pumps, fans, compressors and conveyors a smooth start without the 6 to 8 times rated current of a direct-on-line start, in a compact unit with built-in motor protection.

In this article

• Why fixed-speed motors still need soft starting
• How the ATS22 works
• Setting the starting current
• Sizing the ATS22: in line or inside delta
• Installation rules that protect the starter
• ATS22 versus other starting options
• Where the ATS22 is used
• Lessons from our soft starter projects
• How to select an ATS22
• Frequently asked questions about the Schneider ATS22
• Sources

This guide explains how the ATS22 works, how to size and install it correctly in a Singapore switchboard, where it fits against other starting methods, and what we have learned commissioning soft starters on HVAC and fire pump systems.

Why fixed-speed motors still need soft starting

Many motors do not need variable speed. A fire pump, a fixed-duty transfer pump or a fully loaded compressor runs at full speed whenever it runs. The US Department of Energy’s Adjustable Speed Drive tip sheet notes that variable speed drives do not save energy on equipment that operates close to fully loaded most of the time.

These motors still face the starting problem. Schneider Electric’s guide to DOL starters puts the starting current of a motor switched straight onto the supply at typically 6 to 8 times its rated running current. That surge dips the supply for other equipment, and the sudden torque stresses couplings, belts and pipework. A soft starter solves the start without adding the cost and complexity of a drive.

How the ATS22 works

The ATS22 controls the voltage applied to the motor with thyristors during starting and stopping. Soft starters of this kind are covered by IEC 60947-4-2, the standard for semiconductor motor controllers, starters and soft starters up to 1,000 V AC. Our ATS22 product page lists its key functions:

• Torque control and current limiting during acceleration and deceleration.
• Integrated bypass contactor, which takes over once the motor is at speed, reducing installation complexity.
• Integrated display and adjustment controls for set-up at the panel.
• Protection functions including thermal overload, phase loss and other motor protection.

Schneider’s Singapore product page for the ATS22D47Q adds the practical benefits Schneider claims for the range: smooth starting that avoids mechanical stresses and extends service life, reduced noise for operators, a slim form factor, lower cost to stock spares, and the ability to overcome difficult or high-torque starts. It also publishes motor thermal protection trip curves for a standard Class 10 application.

Setting the starting current

The current limit is the main lever on a soft starter. Schneider’s ATS22 FAQ states that the current can be limited from 200% to 700% of motor rated current, with a default of 350%.

Set it too low and the motor may struggle to reach full speed; set it too high and the benefit over DOL shrinks. The right value is confirmed during commissioning with the actual load.

Sizing the ATS22: in line or inside delta

The ATS22 range runs from 4 kW to 400 kW, according to Schneider’s Altistart 22 range page, with each reference covering a band of motor ratings by supply voltage. The ATS22D47Q, for example, covers 11 kW to 22 kW across 230 V to 440 V.

The starter can also be connected inside the motor’s delta windings, where it carries the winding current rather than the line current. Schneider’s ATS22 product documentation gives this worked example:

1. A 400 V, 110 kW motor has a line current of 195 A in delta connection.
2. The current in each winding is 195 ÷ 1.5, or 130 A.
3. The soft starter is chosen with a permanent nominal current just above 130 A, rather than above 195 A.

Inside-delta connection needs a motor with six accessible terminals and specific wiring, which Schneider documents in the ATS22 user manual. Confirm the motor’s terminal arrangement before choosing this option.

Installation rules that protect the starter

Schneider’s ATS22 installation guidance includes several points that matter in Singapore plant rooms, where ambient temperatures and humidity can be high:

• ATS22 soft starters are open devices and must be mounted in a suitable enclosure.
• The range is rated for pollution degree 2 under IEC 60664-1; for pollution degree 3, install inside a cabinet rated IP54.
• Mount within ±10° of vertical and away from heat-radiating equipment.
• Leave free space for air to circulate from bottom to top, and provide enclosure ventilation or forced cooling to limit the ambient temperature around the starter.
• If several starters share a panel, arrange them in a row rather than stacking them, so heat from one does not affect the one above.

ATS22 versus other starting options

For pumps, a controlled stop is as valuable as a soft start. The US Department of Energy and Hydraulic Institute sourcebook Improving Pumping System Performance warns that rapid acceleration of large volumes of fluid can cause damaging water hammer, and that soft-starting switchgear can extend system life and improve reliability.

Where the ATS22 is used

• Building services: chilled-water, condenser-water and domestic transfer pumps, cooling tower fans and AHU fans running at fixed speed.
• Water treatment: transfer and process pumps.
• Industry: screw compressors, conveyors and material handling.
• Standby and fire duties: subject to the Fire Code and the consultant’s design.

For fire pump circuits, SCDF’s Fire Code 2023, clause 5.2.3 states that thermal overload trips shall not be used in the motor circuits it covers and requires automatically resetting no-volt release, so the soft starter’s protection settings on these circuits must be configured to suit.

Lessons from our soft starter projects

Our published soft starter references use Himel’s HASXS Expert Series, and the commissioning lessons apply equally to the ATS22:

• Starters can extend the life of existing motors. At Gateway East, we supplied more than ten soft starters from 37 kW to 55 kW as standby starters for the chilled-water and condenser-water systems. A key requirement was that they reliably start motors more than ten years old, so the client could keep its installed motors.
• Critical duties need verified parameters. On the Singapore Rail Test Centre (132 kW) and Kim Chuan Depot Extension (160 kW) fire pump systems for the Land Transport Authority, the starter parameters were configured for the fire pump application and verified through testing and commissioning.

Trans-Digi Global is an authorised partner for Schneider Electric and Himel and also supplies the Carlo Gavazzi RSGD and Himel HASES soft starters. Where the specification names the ATS22, we supply it; where it is open, we compare options on duty, lead time and cost. Our services cover sizing, panel integration, parameter set-up, testing and commissioning.

How to select an ATS22

1. Motor rating and voltage: kW and full-load current at 230 V, 400 V or 440 V.
2. Connection: in line, or inside delta for six-terminal motors.
3. Load type: centrifugal pump or fan (light start) or high-inertia load (heavy start).
4. Starts per hour and starting time: check against the starter’s rating.
5. Supply limits: maximum acceptable starting current, especially on generator supply.
6. Enclosure and ventilation: pollution degree, IP rating and heat dissipation.
7. Fire Code duties: confirm any SCDF requirements for the circuit.

Frequently asked questions about the Schneider ATS22

What is the Schneider ATS22 used for?

It is an all-in-one soft starter for three-phase asynchronous motors from 4 kW to 400 kW, used on pumps, fans, compressors and conveyors that run at fixed speed.

Does the ATS22 have a built-in bypass?

Yes. The ATS22 has an integrated bypass contactor that takes over once the motor reaches speed, which reduces installation complexity.

How much does the ATS22 reduce starting current?

The current limit is adjustable from 200% to 700% of motor rated current, with a 350% default, compared with typically 6–8 times rated current for a direct-on-line start.

Can the ATS22 be connected inside the motor delta?

Yes, on motors with six accessible terminals. The starter then carries the winding current, roughly the line current divided by 1.5, so a smaller unit can be used.

Should I choose the ATS22 or a variable speed drive?

Choose the ATS22 when the motor runs at fixed speed and you only need a smooth start and stop. Choose a drive when the load varies and running at lower speed will save energy.

Where can I buy the ATS22 in Singapore?

Send the motor rating, voltage, application and quantity through our contact page. For larger or more demanding duties, see our guide to the Schneider ATS480, and for variable loads, how VSDs improve motor efficiency.

Sources

• Schneider Electric Singapore, Altistart 22 range page.
• Schneider Electric Singapore, ATS22D47Q product page, installation and connection guidance.
• Schneider Electric, FAQ: How to reduce starting current in ATS22.
• Schneider Electric, DOL starter: types and working principle.
• IEC, IEC 60947-4-2:2020 Semiconductor motor controllers, starters and soft-starters.
• US Department of Energy, Motor Systems Tip Sheet #11.
• US Department of Energy and Hydraulic Institute, Improving Pumping System Performance: A Sourcebook for Industry.
• Singapore Civil Defence Force, Fire Code 2023, clause 5.2.
• Trans-Digi Global project references: Gateway East, Singapore Rail Test Centre, Kim Chuan Depot Extension.