Electrical power system

A method of operating an electrical power system comprising:

• an electrical machine;
• an AC:DC power electronics converter connected to receive an input AC supply from the electrical machine and provide an output DC supply across first and second output terminals;
• a DC bus connected to the first and second output terminals of the AC:DC power electronics converter;
• a load connected across the DC bus;
• a first circuit breaker switch and a first current limiting diode connected in series between the AC:DC power electronics converter and the DC bus;
• and
• a second circuit breaker switch and a second current limiting diode connected in series between the DC bus and the load the first current limiting diode being configured to limit current to a higher level than the second current limiting diode,
• the method comprising:
• measuring a voltage across the first and second current limiting diodes;
• opening the first circuit breaker switch if the measured voltage across the first current limiting diode exceeds a first threshold voltage;
• and
• opening the second circuit breaker switch if the measured voltage across the second current limiting diode exceeds a second threshold voltage.

An electrical power system comprising:

• an electrical machine;
• an AC:DC power electronics converter having an AC side and a DC side, the AC side connected to the electrical machine and the DC side connected across first and second terminals;
• a DC bus connected to the first and second terminals of the AC:DC power electronics converter;
• a load connected across the DC bus;
• a first circuit breaker switch and a first current limiting diode connected in series between the AC:DC power electronics converter and the DC bus;
• and
• a second circuit breaker switch and a second current limiting diode connected in series between the DC bus and the load,
• wherein the first current limiting diode is configured to limit current to a higher level than the second current limiting diode.