Monitoring an electrical machine for the presence of a fault

A method for operating an electric machine of an electrical system in dependence on an operating state of the electrical system, the method comprising:

• determining, during the operation of the electric machine, at least one group of evaluation variables for a multiphase time signal that is transmitted momentarily from or to the electric machine in such a way that in each case an evaluation variable of the group of evaluation variables is determined for at least two different phases of the multiphase time signal;
• comparing, in an evaluation circuit, each of the determined evaluation variables of the respective group of evaluation variables with every other of the determined evaluation variables of the respective group;
• and
• establishing the operating state of the electrical system based on the comparison,
• wherein the operating state is a normal operating state, a warning operating state, or an alarm operating state, and
• wherein, for each phase of the multiphase time signal, a Hilbert filter is applied to the respective phase of the multiphase time signal to determine the respective evaluation variable.

A method for operating an electric machine of an electrical system in dependence on an operating state of the electrical system, the method comprising:

• determining, during the operation of the electric machine, at least one group of evaluation variables for a multiphase time signal that is transmitted momentarily from or to the electric machine in such a way that in each case an evaluation variable of the group of evaluation variables is determined for at least two different phases of the multiphase time signal;
• comparing, in an evaluation circuit, each of the determined evaluation variables of the respective group of evaluation variables with every other of the determined evaluation variables of the respective group;
• and
• establishing the operating state of the electrical system based on the comparison, wherein the operating state is a normal operating state, a warning operating state, or an alarm operating state,
• wherein the operating state is a normal operating state, a warning operating state, or an alarm operating state, and
• wherein, in the comparison of the evaluation variables of the different phases of the multiphase time signal with one another, the respective result of the comparison for a respective group is determined by forming a difference or by forming a quotient of two evaluation variables of the respective group that are in each case to be compared.

A monitoring unit comprising:

• an electrical interface for connecting the monitoring unit to an electrical line, which carries a multiphase time signal transmitted momentarily from or to an electric machine of an electric system;
• a filter for determining evaluation variables, which is configured to be connected to the electrical line by way of the electrical interface;
• and
• an evaluation circuit connected to the filter, wherein the evaluation variables determined by the filter are configured to be fed to the evaluation circuit,
• wherein the filter is configured to determine, during operation of the electric machine, at least one group of evaluation variables for the multiphase time signal that is transmitted momentarily from or to the electric machine and is fed to the filter by way of the electrical interface, in such a way that in each case one evaluation variable of the group of evaluation variables is determined for at least two different phases of the multiphase time signal, and
• wherein the evaluation circuit is configured to compare each of the determined evaluation variables of the respective group of evaluation variables with every other of the determined evaluation variables of the respective group of evaluation variables and, in dependence on a respective result of the comparison, to produce a control signal, which serves as a basis for establishing an operating state of the electrical system.

An electrical system comprising:

• an electric machine;
• and
• a monitoring unit comprising:
• an electrical interface for connecting the monitoring unit to an electrical line, which carries a multiphase time signal transmitted momentarily from or to the electric machine;
• a filter for determining evaluation variables, which is configured to be connected to the electrical line by way of the electrical interface;
• and
• an evaluation circuit connected to the filter, wherein the evaluation variables determined by the filter are configured to be fed to the evaluation circuit,
• wherein the filter is configured to determine, during operation of the electric machine, at least one group of evaluation variables for the multiphase time signal that is transmitted momentarily from or to the electric machine and is fed to the filter by way of the electrical interface, in such a way that in each case one evaluation variable of the group of evaluation variables is determined for at least two different phases of the multiphase time signal, and
• wherein the evaluation circuit is configured to compare each of the determined evaluation variables of the respective group of evaluation variables with every other of the determined evaluation variables of the respective group of evaluation variables and, in dependence on a respective result of the comparison, to produce a control signal, which serves as a basis for establishing an operating state of the electrical system.