Electrical power supply system for a programmable logic controller

An electrical power supply system for a programmable logic controller, the electrical power supply system comprising:

• a first electrical power supply module configured to operate in a master mode to deliver at least one electrical supply voltage to the programmable logic controller;
• a second electrical power supply module configured to operate in a slave mode to deliver the electrical supply voltage to the programmable logic controller in event of failure of the first electrical power supply module;
• and
• a first microcontroller and a second microcontroller each including:
• a control module configured to temporarily control switching of the first electrical power supply module to the slave mode and switching of the second electrical power supply module to the master mode, and
• a test module configured to test the second electrical power supply module in current when the second electrical power supply module is switched to the master mode, the test module being configured to measure electric current delivered by the second electrical power supply module when the second electrical power supply module is in the master mode,
• wherein the first and second microcontrollers communicate to implement the test by the respective test modules, and
• wherein each control module is configured to, after the test is completed and the electric current delivered by the second electrical power supply module when the second electrical power supply module is in the master mode is measured, control switching of the first electrical power supply module back to the master mode and switching of the second electrical power supply module back to the slave mode.