ABB PSR25-600-70 Compact Soft Starter, 25 A

The PSR25-600-70 is the 25 A size of ABB’s compact PSR softstarter range, ordered as 1SFA896108R7000. It starts and stops a three-phase squirrel-cage motor along a voltage ramp, so the shaft sees a gentle torque build-up instead of the across-the-line jolt. The built-in bypass closes after the ramp, so continuous running produces little heat, and only two phases are controlled. It is intended for 11 kW class motors where a top-of-ramp signal is wanted, within the pump, fan, compressor and conveyor duties ABB describes.

See motor soft starters for the full list, and the PSR30-600-70 for a 30 A alternative.

Technical specifications

Duty limits of the PSR25

Select by motor current. The 25 A rating is a limit, and the kW values in the table are only the matching IEC and UL motor sizes. ABB’s starts-per-hour data assume 40 C ambient, a starting current of 4 x Ie and a 6 second ramp; under those conditions the PSR25 handles a 25 A motor at 10 starts per hour without a fan and 20 with the auxiliary fan. Between 40 C and 60 C derate by 0.8 percent for every degree. For installations higher than 1000 m use the formula percent of Ie = 100 – (x – 1000)/150, where x is the altitude in metres; 4000 m is the maximum. Heavier starting duty is outside these tables; use ABB’s selection tool or the next frame.

In the catalogue the PSR25 is paired with the MS132 manual motor starter, 50 A gG fuses (50 kA), a 60 A J-type fuse for UL, an overload relay of type TF42 and a line contactor of type AF26. The contactor does not serve the softstarter, yet is often fitted to let the overload relay disconnect the circuit. Accessories include a connection kit for the manual motor starter and the PS-FBPA fieldbus plug adapter. ABB points to its coordination tool for alternative protection devices.

Mounting, indicators and settings

It is built in the PSR25 to PSR30 frame: IP20 main circuit and control circuit, 12 VA at 100-240 V AC, DIN rail or screw fixing. Ramp and voltage limits are set on three dials, and two LEDs report On/Ready and Run. A narrow housing saves enclosure space. Leave the clearances given in the manual for cooling.

PSR-70 range: neighbouring types and order codes

ABB lists these neighbouring sizes for the same control voltage.

Worked derating examples for the PSR25

The derating rules above can be applied directly. At 50°C ambient, ten degrees above the 40°C reference, the current is reduced by 10 x 0.8 = 8 percent, so the PSR25 should be used for a motor of no more than about 23 A. At 55°C the reduction is 12 percent, leaving about 22 A. These figures matter in Oman, where unconditioned panels in pump houses and on skids regularly exceed 40°C inside the enclosure during summer. If the motor current is close to 25 A and the panel is not air-conditioned, the PSR30 is the more comfortable choice.

Starts per hour in practice

The rating of 10 starts per hour without a fan assumes a 6 s ramp at 4 x Ie. Longer ramps or higher starting current produce more heat in the thyristors, so applications such as booster pumps that cycle often, or conveyors that restart under load, should be checked with ABB’s selection tool. Adding the auxiliary fan doubles the permitted starts under the reference conditions.

Setting the three dials

• Start ramp (1–20 s): begin with a short ramp and extend it until the mechanical shock disappears. An unnecessarily long ramp only adds heat.
• Stop ramp (0–20 s): on pumps a soft stop reduces pressure surges and water hammer. On fans and other high-inertia loads it is usually set to 0 so the load coasts down.
• Initial/end voltage (40–70 %): raise it if the motor does not begin to turn at once at the start of the ramp; keep it as low as possible otherwise.

Typical applications in Oman and the GCC

An 11 kW motor at 400 V is a common size for water transfer and irrigation pumps, cooling tower fans, small air compressors and belt conveyors in quarries and cement plants. In these duties the PSR25 reduces the starting current peak compared with direct-on-line starting, which helps on weak supplies or generator-fed sites, and reduces belt slip and coupling wear. Because the PSR has IP20 protection, it must be installed in a dust-protected enclosure; in sandy locations use filtered ventilation and clean the filters regularly. The motor itself still needs separate overload protection such as the TF42 relay listed above.

Type code, order check and documents

The PSR25-600-70 code reads: PSR family, size 25, 600 V class, -70 for a 100-240 V AC control supply (the 24 V AC/DC type ends -11). Before ordering confirm motor current, line voltage, control voltage, starts per hour and accessories such as the connection kit or fan.

The PSR pages of ABB catalog 1SFC132012C0201 are provided, covering ordering details, technical data, dimensions and circuit diagrams. Quotations are prepared on request by Seven Star LLC, an independent supplier in Muscat, and this page shows no price or stock.