ABB PSR37-600-70 Compact Soft Starter, 37 A

Choose the PSR37-600-70, ABB order code 1SFA896110R7000, when a motor of up to 37 A rated operational current needs a smooth, adjustable start and stop in a very small package. Starting and stopping follow an adjustable voltage ramp, reducing mechanical wear compared with direct-on-line switching. The built-in bypass closes after the ramp, so continuous running produces little heat, and only two phases are controlled. ABB names pumps, fans, compressors and conveyors as typical duties, and this size suits 18.5 kW class motors on larger pumps and compressors.

Related equipment is listed under motor soft starters, including the neighbouring PSR30-600-70 size.

Technical specifications

Matching the PSR37 to the motor and the starts per hour

Select by motor current. The 37 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 PSR37 handles a 37 A motor at 10 starts per hour without a fan and 20 with the auxiliary fan. Above 40 C and up to 60 C the rated current falls by 0.8 percent per 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. For heavy starts or higher starting rates ask ABB’s softstarter selection tool, or step up a size.

ABB’s example coordination for the PSR37 uses manual motor starter MS165 (type 1, 50 kA), a 100 A gG fuse, J-type fuses up to 90 A for UL, thermal overload relay type TF42 and line contactor type AF38. The contactor does not serve the softstarter, yet is often fitted to let the overload relay disconnect the circuit. Kits for direct connection to ABB manual motor starters are available, as is the PS-FBPA fieldbus plug adapter. Other short-circuit protection devices can be checked in ABB’s online coordination tool.

Installation of the PSR37

Housing group PSR37 to PSR45 applies, with IP10 main circuit, IP20 control circuit and 10 VA at 100-240 V AC; the starter mounts on a DIN rail or with screws. Setup uses three potentiometers for the start ramp, the stop ramp and the initial or end voltage; green LEDs show On/Ready and Run. Several units can share one enclosure because the housing is narrow. Check ventilation clearances in the manual before stacking units.

Sizes next to the PSR37

ABB lists these neighbouring sizes for the same control voltage.

Applying the derating rules to the PSR37

Using ABB’s figure of 0.8 percent per degree above 40°C, a PSR37 in an enclosure at 50°C is good for about 34 A, and at 55°C for about 32.5 A. A typical 18.5 kW 400 V motor draws a current in the mid-thirties, so in a hot, unconditioned panel the margin disappears quickly. In such cases the PSR45 or an air-conditioned enclosure should be considered. Note also that the main circuit of this frame is IP10, so terminals must be protected against accidental contact by the enclosure itself.

Heat and enclosure design

Thanks to the integrated bypass, the stated power loss at Ie is only 5.5 W, so the soft starter adds little heat during continuous running. Most of the heat is generated during the start ramp. For panels with several starters, size the ventilation for the case where motors start in sequence, and keep the clearances from the manual.

Commissioning checklist

• Check that the main supply is within 208–600 V and the control supply is 100–240 V AC; the -70 version does not accept 24 V.
• Set the start ramp, stop ramp and initial voltage before the first start; begin with a moderate ramp and adjust while watching the load.
• Use the run relay (3 A resistive, 0.5 A AC-15) to signal the PLC or to switch a line contactor where required.
• Verify that the overload relay is set to the motor nameplate current.
• Observe the first starts and confirm that the Run LED comes on and the bypass closes at the end of the ramp.

Where the PSR37 fits in GCC plants

The 18.5 to 22 kW range covers larger booster and transfer pumps in water networks, chilled water and condenser pumps in district cooling, screw compressors, and crusher feeders and conveyors. Soft stopping on pumps reduces water hammer in long pipelines, which is valuable in desalinated water transfer systems. Where the motor is fed from a diesel generator, the reduced inrush helps keep voltage dips within acceptable limits. In dusty locations install the unit in a sealed or filtered enclosure.

Ordering notes and documents

The PSR37-600-70 code reads: PSR family, size 37, 600 V class, -70 for a 100-240 V AC control supply (the 24 V AC/DC type ends -11). Please confirm the motor current, supply voltage, control voltage, starts per hour and any connection kit or fan before ordering.

The linked document is the PSR section of ABB’s softstarter catalog (1SFC132012C0201) with ordering details, technical data and circuit diagrams. Seven Star LLC is an independent supplier in Muscat and quotes on request; no price or stock is shown on this page.