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Soft Starter for Pump

Soft starter for a pump: when we ship one, and when a contactor will do

We ship a soft starter for a pump in two cases: when the pipeline has thin walls or old cast-iron joints that won't survive water hammer, or when the motor inrush trips the main breaker on start. Most of our customers are water-utility crews running a 11-22 kW station where post-repair pressure spikes are tearing joints apart, or a farmer with a 7.5-15 kW borehole pump whose check valve starts leaking a week after install.

How it works. The soft starter limits start voltage, ramping it up over 5-15 seconds instead of an instant connection. Inrush drops from 6-7×FLA to 3-4×FLA (from the datasheet, not from marketing), pipe pressure builds gradually, mechanical seals last 2-3 times longer. Once the motor is up to speed, the internal bypass contactor switches it to direct supply and the thyristors cool off. If you also need to control pump output by pressure or flow, take a VFD instead.

What we ask before the order

First: the exact pump model and the nameplate current. You can't size by kW alone, because submersible pump efficiency drifts. Second concern: is the pump a borehole unit with a long cable run (50+ meters). If yes, add a 25-30% current margin, because cable inductance makes the start heavier. We also ask about soft stop: it matters for pumps with a check valve at 15-30 m height, otherwise the water column drops back and slams the impeller.

From our 12-month sales the top 3 for pumps: Schneider ATS22D47Q (47 A, 22 kW, centrifugals at water utilities), ATS22D32Q (32 A, 15 kW, typical borehole), ATS01N222QN (22 A, circulation pumps in boiler rooms). Manufacturer warranty 12-24 months depending on series, delivery from our Kyiv warehouse in 1-3 days.

ModelSeriesRated CurrentApplication
Schneider Electric ATS22D47QATS2247 ACentrifugal pumps 22 kW
Schneider Electric ATS22D32QATS2232 ABorehole pumps 15 kW
Schneider Electric ATS01N232QNATS0132 AWater supply systems
Schneider Electric ATS01N222QNATS0122 ACirculation pumps
Siemens 3RW3016-1BB14SIRIUS 3RW309 ADomestic pumps

Soft Starter Manufacturers for Pumps

Our catalog features soft starters from leading global industrial automation manufacturers:

  • Schneider Electric: Altistart series ATS01, ATS22, ATS48, ATS130. The most popular choice for pump applications with built-in dry run and water hammer protection.
  • Danfoss: MCD200 series. Compact soft starters with an extended supply voltage range.
  • Siemens, SIRIUS 3RW30/3RW40 series. Reliable soft starters for industrial pumping stations.

Soft Starters by Application

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Warranty and Delivery

All soft starters for pumps come with an official manufacturer warranty of 12 to 24 months. Delivery across Ukraine: Kyiv, Kharkiv, Odesa, Dnipro, Lviv; other cities on request. Bank transfer for businesses or cash on delivery for individuals.

Frequently Asked Questions

Soft starter or VFD for a pump?

It splits by the job. A soft starter removes the jolt at start and stop; once up to speed the motor runs straight off the mains through a bypass. It does not hold speed and saves no energy while running. A VFD controls speed the whole time, so it does what a soft starter cannot: pressure control from a sensor via PID, sleep mode, dry-run protection. Pumping into a float-switched tank: take a soft starter. Steady mains pressure, or a borehole with frequent draw-off? Then a VFD.

Which soft starter suits a borehole pump?

We size it by the motor current from the nameplate, not by kilowatts guessed at. The smallest units in stock start at 4 A (ABB PSR), 5 A (Motortronics VMX-PFE-02) and 6 A (Schneider ATS01N103FT, 1.1 kW at 400 V). A borehole adds one thing: the motor starts loaded by the water column. We do not trim the frame size here and take one class above what a one-to-one calculation gives.

Can a soft starter be used on a 220 V pump?

The industrial soft starters we sell (Schneider Altistart, ABB PSR and PSTX, Danfoss MCD, Siemens SIRIUS, Veichi SS70, WEG SSW) drive three-phase motors. A single-phase pump such as the Ukrainian "Vodoley" has a capacitor start winding, and phase-angle control works poorly with it. The working route for 220 V is different: a single-phase VFD, 1×220 V, for example the Veichi AC01. Domestic soft-start relays for 2.2-3 kW exist, but they are a different class of device.

Does a pump station need a soft starter?

If the station cuts in several times an hour and the pipes knock at every start, yes. Water hammer hits fittings and valves harder than it hits the pump itself. There is a limit though: a soft starter does not remove frequent starts, it only softens them. When a station clicks every minute the cause is usually the pressure vessel, or the system actually needs pressure regulation, and that means a VFD with PID.

How is a soft starter wired to a pump?

The layout is standard: breaker, contactor, soft starter, motor. Start and stop commands go to the digital inputs of the unit, not by breaking the power circuit. Two places where people get it wrong. First, the old thermal overload relay is left in the circuit after installation, although modern soft starters have built-in motor protection that works more accurately. Second, most units are not rated for starting more often than once every 10 minutes. For the wiring of a specific model see the manual on its product page.