Description:
The ABB 1SF536268D1008 is the main control / motherboard PCB (also referred to as the CPU or logic board) used inside ABB’s PSTX series electronic soft starters — covering the PSTX30 through PSTX1250 (certain frame sizes) as well as selected PSR / PSC / PST(B) legacy units that share the same control-platform lineage. It is the intelligence of the soft starter: the board houses the microprocessor that executes the soft-start / soft-stop ramp algorithms (including ABB’s patented TRI LOGIC® for torque-controlled starting), monitors motor current and thyristor heatsink temperature via the power-section sensing links, drives the thyristor gate pulses through an isolated interface, manages the bypass-contactor control, and stores application parameters in non-volatile memory. The 1SF536268D1008 also provides the connection point for the front keypad/LCD (or remote operator panel) and optionally for a fieldbus piggyback module (Modbus RTU / Profibus / DeviceNet depending on accessory).
Application Scenarios:
A large water-treatment plant operates multiple 315 kW centrifugal pumps on ABB PSTX370 soft starters. During a hot summer afternoon, one starter faulted to “Control Board Failure / EEPROM Error” and would not reset via the front panel or by cycling power. The pump was critical to maintaining wet-well level. Maintenance verified 110 V AC control voltage was present and reseated the ribbon to the keypad — the fault persisted, indicating a failed ABB 1SF536268D1008 motherboard. A pre-verified spare was installed (after isolating main power and discharging the DC bus), the original DIP / jumper settings were replicated, and the starter booted normally — loading its parameter set from the onboard NVRAM. The pump was back online within 20 minutes, avoiding a bypass around the soft starter that would have subjected the motor to a damaging across-the-line start and potentially tripped the upstream MCCB. The 1SF536268D1008 directly solved the pain point of a “brain-dead” soft starter — when this board fails the thyristors cannot fire and the motor cannot start, making it the single highest-priority spare for any PSTX-equipped facility.
Parameter:
| Main Parameters | Value/Description |
|---|---|
| Product Model | 1SF536268D1008 (PSTX Series Main Control / Motherboard PCB) |
| Manufacturer | ABB (Drives / Motion — Low Voltage Products & Systems) |
| Product Category | Soft Starter Control Board / CPU Motherboard (PSTX Family) |
| Compatible Starters | ABB PSTX30 … PSTX570 (some references extend to PSTX1250 — verify BOM / frame size before order) |
| Microprocessor | 16-bit / 32-bit MCU (version-dependent) executing ramp, current-limit & TRI LOGIC® algorithms |
| Memory | NVRAM / EEPROM for parameter storage; retentive across power cycles |
| Inputs (Control Side) | Run / Stop / Reset DI (24 V DC or 110/230 V AC per version); optional remote DI expansion via add-on |
| Outputs (Control Side) | Bypass contactor drive (relay or SSR), Fault Relay (NO/NC), Ready / Running status |
| Thyristor Interface | Isolated gate-drive & feedback via multi-pin header to power-section firing board |
| Sensing Inputs | Motor current (CT secondary from power section), heatsink temperature (NTC/PTC from thyristor module) |
| Keypad / Display | Ribbon cable to PSTX front panel (2-line alpha-numeric + LEDs) or remote mount kit |
| Option Slot | Supports fieldbus piggyback (Modbus RTU / Profibus DP / DeviceNet — sold separately) |
| Supply Voltage | Derived from soft starter control-voltage input (typically 100–240 V AC or 24 V DC — per starter P/N) |
| Coating / Protection | Conformal coated PCB; IP00 (must be installed inside starter enclosure) |
| Operating Temp. | -10 °C to +50 °C (inside starter cabinet; derate above 40 °C per manual) |
| Dimensions (approx.) | 150 × 110 × 30 mm (form factor varies by PSTX frame size — confirm against removed unit) |
Technical Principles and Innovative Values:
The ABB 1SF536268D1008 is purpose-built for reliable, repeatable motor starting — not a generic motor-controller card.
- Innovation Point 1 — TRI LOGIC® Torque-Controlled Starting & Kick-Start Feature: The onboard firmware implements ABB’s TRI LOGIC® algorithm which modulates starting torque in proportion to load requirement rather than blindly ramping voltage. This reduces mechanical stress on couplings/belts and minimizes starting current spikes — a key advantage over basic voltage-ramp soft starters and a frequent reason plants standardize on PSTX units.
- Innovation Point 2 — Dual-Level Parameter Protection & Auto-Restore: Application parameters (ramp time, initial/final voltage, current limit, bypass delay) are stored in write-protected NVRAM. If a board is replaced, the new 1SF536268D1008 can be pre-loaded from a backup file via ABB’s starter-configuration software, or will adopt the previous unit’s settings if the old EEPROM is transplanted (version-dependent). This minimizes recommissioning time.
- Innovation Point 3 — Integrated Bypass Logic with Reduced Heat & Energy: The control board automatically closes the external bypass contactor once the ramp is complete and motor current has settled below the preset bypass-current threshold. This removes thyristor conduction losses, extends SCR life, and improves overall system efficiency — all sequenced by the 1SF536268D1008 without external timer relays.
