Method and apparatus for control of electrical machines

A method for controlling a synchronous electrical machine comprising an inverter configured to provide a stator excitation signal to one or more stator phase windings of the synchronous electrical machine and an electronic control system comprising a frequency setting section and a magnitude setting section for setting the frequency and magnitude of the stator excitation signal, the method comprising:

• operating the frequency setting section to determine a maximum frequency of the stator excitation signal that is substantially equal to the frequency associated with operation of a rotor of the synchronous electrical machine at a target operating speed;
• operating the frequency setting section to respond to a drop in the operating frequency of the synchronous electrical machine by setting a frequency for the stator excitation signal which substantially follows and maintains synchronism with the operating speed of the synchronous electrical machine;
• and
• in the event of an instantaneous increase in the rotational frequency of the synchronous electrical machine beyond the maximum frequency, operating the frequency setting section to maintain the stator excitation signal at the maximum frequency.

An electronic control system for controlling a synchronous electrical machine and configured to vary a magnitude and frequency of a stator excitation signal applied by an inverter to one or more stator phase windings of the synchronous electrical machine,

• the electronic control system comprising a frequency setting section and a magnitude setting section, wherein:
• the frequency setting section is configured to determine a maximum frequency of the stator excitation signal that is substantially equal to the frequency associated with operation of a rotor of the synchronous electrical machine at a target operating speed;
• the frequency setting section is configured to respond to a drop in the operating frequency of the synchronous electrical machine by setting a frequency for the stator excitation signal which substantially follows and maintains synchronism with the operating speed of the synchronous electrical machine;
• and
• in the event of an instantaneous increase in the rotational frequency of the synchronous electrical machine beyond the maximum frequency, the frequency setting section is configured to maintain the stator excitation signal at the maximum frequency.

A method for controlling a synchronous electrical machine comprising:

• varying, by an electronic control system, a magnitude and frequency of a stator excitation signal applied by an inverter to one or more phase windings of the synchronous electrical machine, wherein the electronic control system includes a frequency setting section and a magnitude setting section;
• determining, by the frequency setting section, a maximum frequency value from a target operating speed of the synchronous electrical machine;
• limiting, by the frequency setting section, the frequency of the stator excitation signal to the maximum frequency value;
• responding, by the frequency setting section, to a drop in the operating frequency of the synchronous electrical machine by setting a frequency for the stator excitation signal which substantially follows and maintains synchronism with the operating speed of the synchronous electrical machine;
• and
• in the event of an instantaneous increase in the rotational frequency of the synchronous electrical machine beyond the maximum frequency, maintaining, by the frequency setting section, the stator excitation signal at the maximum frequency.