An electrical power supply system for a programmable logic controller, including: 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; 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 when the second electrical power supply module is switched to the master mode.

An electrical power supply system for a programmable logic controller, including: 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; 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 when the second electrical power supply module is switched to the master mode.