ABB PSTX
Softstarter for three-phase motors: start and stop, currents, temperatures and protection events.
The ABB PSTX is a softstarter that starts and stops three-phase motors for pumps, fans, compressors and conveyors, with built-in protection functions. This Modbus RTU template reads phase currents, frequency, motor temperature, run status and event codes and lets you start, stop and reset the softstarter from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 19200 baud
- Registers
- 60, read and write
- Brand
- ABB
- Key readings
- Run and top of ramp status · Phase currents · Mains frequency · Motor voltage · Motor temperature · Number of starts · Motor run time · Top event code
- Available commands
- Start and stop · Fault reset · Relay outputs · Control words
- Compatible models
- PSTX30 to PSTX1250 softstarters with built-in Modbus RTU
- Last updated
Registers (60)
28 read, 32 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Status Word | Read | ||||
| FBT Return Value | Read | ||||
| Fieldbus AI 1 (Phase L1 Current) | A | Read | |||
| Fieldbus AI 2 (Phase L2 Current) | A | Read | |||
| Fieldbus AI 3 (Phase L3 Current) | A | Read | |||
| Fieldbus AI 4 (Max Phase Current) | A | Read | |||
| Fieldbus AI 5 (Mains Frequency) | Hz | Read | |||
| Fieldbus AI 6 (Motor Voltage) | % | Read | |||
| Fieldbus AI 7 (Motor Temperature) | °C | Read | |||
| Fieldbus AI 8 (Number of Starts) | Read | ||||
| Fieldbus AI 9 (Motor Run Time) | h | Read | |||
| Fieldbus AI 10 (Top Event Code) | Read | ||||
| Auto Mode Status | Read | ||||
| Event Status | Read | ||||
| Ready to Start | Read | ||||
| FBT Response 0 | Read | ||||
| FBT Response 1 | Read | ||||
| FBT Toggle Bit Input | Read | ||||
| Fieldbus DI 1 | Read | ||||
| Fieldbus DI 2 | Read | ||||
| Fieldbus DI 3 | Read | ||||
| Fieldbus DI 4 | Read | ||||
| Fieldbus DI 5 | Read | ||||
| Fieldbus DI 6 | Read | ||||
| Fieldbus DI 7 | Read | ||||
| Fieldbus DI 8 | Read | ||||
| Fieldbus DI 9 | Read | ||||
| Fieldbus DI 10 | Read | ||||
| Start Command | Write | ||||
| Stop Command | Write | ||||
| Fault Reset | Write | ||||
| Auto Mode | Write | ||||
| Slow Speed Reverse | Write | ||||
| Slow Speed Forward | Write | ||||
| Start 1 | Write | ||||
| Start 2 | Write | ||||
| Start 3 | Write | ||||
| Motor Heating | Write | ||||
| Stand Still Brake | Write | ||||
| Start Reverse | Write | ||||
| Emergency Mode | Write | ||||
| FBT Toggle Bit Output | Write | ||||
| User Defined Trip | Write | ||||
| Switch to Remote Control | Write | ||||
| Pump Cleaning Automatic | Write | ||||
| Pump Cleaning Forward | Write | ||||
| Pump Cleaning Reverse | Write | ||||
| K4 Relay Command | Write | ||||
| K5 Relay Command | Write | ||||
| K6 Relay Command | Write | ||||
| 1DO0 Relay Command | Write | ||||
| 1DO1 Relay Command | Write | ||||
| 2DO2 Relay Command | Write | ||||
| 2DO3 Relay Command | Write | ||||
| Refresh Parameters | Write | ||||
| Control Word 1 | Write | ||||
| Control Word 2 | Write | ||||
| FBT Control Word | Write | ||||
| Fieldbus AO 1 | Write | ||||
| Fieldbus AO 2 | Write |
Loading registers…
Send your device list
If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Show phase currents and motor temperature of a pump or fan on a dashboard next to the run status of the softstarter.
- Get an email as soon as the event status bit turns on, together with the top event code, so you know which protection tripped.
- Follow the number of starts and the motor run time to plan maintenance of the motor and the softstarter.
- Reset a fault or switch an output relay remotely when the process allows it, without a visit to the panel.
Installation
Connect terminals 23 and 24 of the PSTX to the RS485 port of the ModbusCloud Gateway and terminate the last device on the line.
On the softstarter set Com3 function to Modbus RTU slave, an address of 1 to 247, 19200 baud, even parity and 1 stop bit, and then FB interface connector to Modbus RTU.
Power cycle the softstarter so the new communication settings take effect.
In ModbusCloud, add a Modbus device (RTU) with the same address and settings, import this template and check that the phase currents arrive.
Things to watch for
The softstarter does not answer on Modbus.
Check that Com3 function is Modbus RTU slave and FB interface connector is Modbus RTU, and that the address is not 0, which is the factory setting. Communication changes need a power cycle. The DX111 and DX112 I/O modules use the same terminals, so they cannot be used together with Modbus.
The softstarter trips on fieldbus failure.
When no Modbus message arrives within the fieldbus failure timeout (19.12), the PSTX trips and stops the motor by default. If you only read values every few minutes, set Fieldbus failure op (19.4) to Off.
The analog values do not match what I expect.
The ten analog values are programmable with Fieldbus AI 1 to 10 (12.22 to 12.31). The template uses the factory functions and scaling, such as phase currents in tenths of an ampere. If someone changed these parameters, the meaning and scaling change too.
Can I start and stop the motor from ModbusCloud?
Yes, with Fieldbus control on and Auto mode set, once writing registers is switched on for your gateway. Use either the command bits or Control Word 1, not both, or the softstarter ignores the commands. A remote start can surprise people working on the machine, so agree on it on site first.
Want to see how it works?
