Apparatus for measuring the electrical time constant of the quadrature-axis damper of a synchronous machine

An apparatus for measuring the electrical time constant of the quadrature-axis damper of a synchronous machine, said synchronous machine having a rotor, a first phase winding, and a second phase winding, said apparatus comprising:

• means for applying a step voltage waveform across said first phase winding and said second phase winding when said rotor is at a position where a quadrature-axis magnetomotive force is generated by a resulting current flowing between said first phase winding and said second phase winding;
• means responsively connected to said first phase winding and said second phase winding for measuring the electrical time constant as a length of a time interval between a first time when a voltage across said first phase winding and said second phase winding reaches a first prescribed value and a second time when said voltage falls to a second prescribed value.

An apparatus for measuring the electrical time constant of the quadrature-axis damper of a synchronous machine, said synchronous machine having a rotor, a first phase winding, and a second phase winding, said apparatus comprising:

• means for applying a step voltage waveform across said first phase winding and said second phase winding when said rotor is at a position where a quadrature-axis magnetomotive force is generated by a resulting current flowing between said first phase winding and said second phase winding;
• means responsively connected to said first phase winding and said second phase winding for measuring the electrical time constant as a length of a time interval between a first time when a voltage across said first phase winding and said second phase winding reaches a first prescribed value as said resulting current reaches a prescribed constant value and a second time when said voltage falls to a second prescribed value which is a prescribed fraction of a difference between said first prescribed value and a threshold value which is a product of a steady-state current flowing through said first and second phase windings and an ohmic resistance of said phase windings.

A method of measuring the electrical time constant of the quadrature-axis damper of a synchronous machine, said synchronous machine having a rotor, a first phase winding, and a second phase winding, said apparatus comprising the steps of:

• placing said rotor in a position at which a quadrature-axis magnetomotive force would be generated by current flowing between said first phase winding and said second phase winding;
• applying a step voltage waveform across said first phase winding and said second phase winding;
• measuring the electrical time constant as a length of a time interval between a first time when a voltage across said first phase winding and said second phase winding reaches a first prescribed value and a second time when said voltage falls to a second prescribed value.