scietex.hal.vfd

The scietex.hal.vfd package is a Python library for interfacing with variable frequency drives (VFD). It defines a transport-agnostic driver contract (VFDProtocol) plus the data structures and capability model shared by every driver, and ships concrete implementations for three drive families.

A driver reaches a drive over one of two transports:

• Direct RS485 — the driver owns the serial port and speaks Modbus RTU to the drive itself (scietex.hal.vfd.base.rs485.VFD).
• Scietex Modbus gateway — the gateway owns the RS485 bus, and the driver speaks Modbus/TCP to a gateway device entry that routes to the drive by unit id (scietex.hal.vfd.intek.spe_b.client.IntekSPEBModbusVFD).

Features

• VFDProtocol, a runtime-checkable contract: connect, disconnect, read parameters, read state, read and reset faults, start, stop and set the frequency setpoint.
• VFDCapabilities, which advertises optional control surface (direction, jog, freewheel stop, fault reset, frequency setpoint) so a caller can reject an unsupported command before dispatching it.
• VFDParameters, which reports frequency in both Hz and percent of the configured maximum, plus output current, voltage and power, and the optional DC bus voltage and temperatures a drive exposes. An optional field is None when the drive does not report it, which is distinct from a reported 0.0.
• Implemented drive models, each with both transports:
  • Intek SPE-B — direct RS485 (SPEvB) and gateway (IntekSPEBModbusVFD).
  • Vesper E5-8200 — direct RS485 (VesperE58200) and gateway (VesperE58200ModbusVFD).
  • Vesper E4-8400 / E4-P8402 — direct RS485 (VesperE48400) and gateway (VesperE48400ModbusVFD).
• Driver descriptors for the gateway (scietex.modbus.drivers entry-point group) and driver classes for a service (scietex.hal.vfd.drivers group).

What each drive reports

Only the E4-8400 exposes a live temperature reading (004Dh, U1-46). The other two report overheat only as a fault code, and a fault is not a temperature.

¹ The SPE-B reports the operating frequency only as a percentage of P0.10, so frequency_hz is None until P0.10 has been read. A drive that refuses P0.10 still reports frequency_percent, current, voltage and power; the connection stays usable and only the Hz field degrades. set_frequency is refused in that state, because no percentage can be computed.

Installation

Install the package via pip (assuming it's published to PyPI):

pip install scietex.hal.vfd

Alternatively, clone the repository and install locally:

git clone https://github.com/bond-anton/scietex.hal.vfd.git
cd scietex.hal.vfd
pip install .

Requirements

• Python 3.10 or higher.
• scietex.hal.serial 2.4 or newer (RS485 transport and Modbus gateway descriptors).
• pymodbus 3.15 or newer (Modbus/TCP client for the gateway transport).

Usage

Every driver implements VFDProtocol: connect, close, read_data, read_parameters, read_state, read_error_code, clear_error, start, stop and set_frequency. Check driver.capabilities before issuing an optional command.

Direct RS485 with the Intek SPE-B VFD:

import asyncio

from scietex.hal.serial import ModbusSerialConnectionConfig
from scietex.hal.vfd.intek import SPEvB


async def main(serial_conf: ModbusSerialConnectionConfig):
    """Main function."""
    vfd = SPEvB(serial_conf, address=1, label="Intek VFD")
    data = await vfd.read_data()
    print(data)


if __name__ == "__main__":
    serial_configuration = ModbusSerialConnectionConfig(
        port="/dev/serial0", baudrate=19200
    )
    asyncio.run(main(serial_configuration))

The same drive behind the Scietex Modbus gateway:

import asyncio

from scietex.hal.vfd.intek import IntekSPEBModbusVFD


async def main():
    """Main function."""
    vfd = IntekSPEBModbusVFD("gateway.local", port=502, unit_id=1)
    await vfd.connect()
    try:
        print(await vfd.read_data())
        print(await vfd.read_error_code())
    finally:
        await vfd.close()


if __name__ == "__main__":
    asyncio.run(main())

A Vesper drive behind the gateway works the same way:

from scietex.hal.vfd.vesper import VesperE48400ModbusVFD

vfd = VesperE48400ModbusVFD("gateway.local", port=502, unit_id=1)

set_frequency takes Hz, not percent: the caller works in engineering units and each driver converts with its own maximum-frequency parameter. The E5-8200's communication manual names no maximum-frequency parameter, so its driver takes max_frequency_hz from the constructor (default 50.0, the factory base frequency); a caller whose drive runs a different maximum must pass it, or frequency_percent will be wrong.

A drive that has never been configured for the gateway answers neither transport. See the per-family references for the register maps, the fault tables and the settings the gateway requires:

• intek/docs/protocol.md — Intek SPE-B (Pd.01/Pd.05/Pd.02).
• vesper/docs/README.md — Vesper E5-8200 and E4-8400, plus the transport facts both manuals share.

Contributing

Contributions are welcome! To contribute:

1. Fork the repository.
2. Create a feature branch (git checkout -b feature/YourFeature).
3. Commit your changes (git commit -m "Add your message").
4. Push to the branch (git push origin feature/YourFeature).
5. Open a Pull Request.

Run the checks before opening a pull request:

tox -e format,lint,type,test

format and lint run ruff, type runs ty, and test runs pytest across Python 3.10, 3.12 and 3.14.

License

This project is licensed under the MIT License - see the LICENSE file for details.