REDUCTION OF START-UP SEQUENCE
The present invention relates to a method for bringing a brushless motor, such as a multiphase brushless motor, operatively connected to for example a compressor into an optimal angular starting position in an energy saving manner, the method comprising the steps of applying a first drive voltage to a first phase winding of the motor and measuring a current flowing in another phase winding of said motor, said current being generated in response to the first drive voltage applied to the first phase winding. The method further comprises the step of switching the applied first drive voltage off when said current reaches a steady-state condition. By applying the method of the present invention a significant amount of power can be saved. The present invention further relates to a system for carrying out the present invention.
1 . A method for efficiently bringing a rotor of a multiphase motor into a desired angular starting position, the method comprising the steps of:
applying a first drive voltage to a first phase winding of the motor,
measuring a current flowing in another phase winding of said motor, said current being generated in response to the first drive voltage applied to the first phase winding, and
switching the applied first drive voltage off when said current reaches a steady-state condition.
2 . The method according to claim 1 , further comprising the steps of:
applying a second drive voltage to a second phase winding of the motor,
measuring a current flowing in another phase winding of said motor, said current being generated in response to the second drive voltage applied to the second phase winding, and
switching the applied second drive voltage off when said current reaches a steady-state condition.
3 . The method according to claim 2 , further comprising the steps of:
applying a third drive voltage to a third phase winding of the motor,
measuring a current flowing in another phase winding of said motor, said current being generated in response to the third drive voltage applied to the third phase winding, and
switching the applied third drive voltage off when said current reaches a steady-state condition.
4 . The method according to claim 1 , wherein steady-state current conditions are considered reached when the oscillations in the current amplitude remain within +/−3% of the total motor current divided by the number of undriven phases.
5 . The method according to claim 1 , wherein the first, second and third drive voltages have amplitudes in the range 10-30 V, such as within the ranges 10-14 V or 22-26 V.
6 . The method according to claim 1 , wherein the first, second and third drive voltages are provided from a battery.
7 . A system for efficiently bringing a rotor of a multiphase motor into a desired angular starting position, the system comprising:
means for generating a drive voltage to be applied to a phase winding of the motor,
means for measuring a current flowing in another phase winding of said motor in response to the drive voltage, and
means for determining when said current reaches a steady-state condition.
8 . The system according to claim 7 , further comprising filter means for filtering a voltage representing a measured current.
9 . The system according to claim 8 , the filter means comprises a low-pass filter.
10 . The system according to claim 7 , wherein the drive voltage has an amplitude in the range 10-30 V, such as within the ranges 10-14 V or 22-26 V.
11 . The system according to claim 7 , further comprising a battery adapted to provide the drive voltage.