Method for controlling a voltage/frequency converter controlled single-phase or polyphase electric motor
First Claim
1. A method for controlling a voltage/frequency converter controlled single-phase or polyphase electric motor (PM) with which to the converter (10) there is supplied a variable for control which corresponds to the induced voltage (16, 17) in at least one phase winding (1, 2, 3) of the motor (PM), characterized in that the intrinsic induction (BEMF) of the at least one motor phase winding (1, 2, 3) is measured and it is evaluated whether the phase position of the intrinsic induction is in a predetermined ratio or not to that of the phase winding current (15) of a motor phase winding (1, 2, 3), and that when the phase positions are not at this predetermined ratio and that of the intrinsic induction (16, 17) leads that of the phase winding current (15) with respect to this ratio, the variable supplied to the converter is produced such that the converter increases the frequency supplied to the motor in the next control interval and/or reduces the voltage supplied to the motor in the next control interval until the phase positions of the intrinsic induction (16, 17) and of the phase winding current (15) are at the predetermined ratio, and when the phase position of the intrinsic induction (16, 17) lags that of the phase winding current (15) with respect to this ratio, the variable (V, F) supplied to the converter (10) is produced such that the converter reduces the frequency supplied to the motor in the next control interval and/or increases the voltage supplied to the motor in the next control interval, until the phase positions of the intrinsic induction (16, 17) and of the phase winding current (15) are at this predetermined ratio.
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Abstract
The method for controlling a voltage/frequency converter controlled single-phase or polyphase electric motor evaluates the phase shifting between the EMF and BEMF by way of the deviation between the zero crossing of the phase current and the voltage produced by the intrinsic induction and readjusts the frequency of the converter accordingly. The measurement of the intrinsic induction is effected in the zero crossing of the current courses of the associated phase, wherein during the measurement the phase is separated from the supply network.
103 Citations
16 Claims
- 1. A method for controlling a voltage/frequency converter controlled single-phase or polyphase electric motor (PM) with which to the converter (10) there is supplied a variable for control which corresponds to the induced voltage (16, 17) in at least one phase winding (1, 2, 3) of the motor (PM), characterized in that the intrinsic induction (BEMF) of the at least one motor phase winding (1, 2, 3) is measured and it is evaluated whether the phase position of the intrinsic induction is in a predetermined ratio or not to that of the phase winding current (15) of a motor phase winding (1, 2, 3), and that when the phase positions are not at this predetermined ratio and that of the intrinsic induction (16, 17) leads that of the phase winding current (15) with respect to this ratio, the variable supplied to the converter is produced such that the converter increases the frequency supplied to the motor in the next control interval and/or reduces the voltage supplied to the motor in the next control interval until the phase positions of the intrinsic induction (16, 17) and of the phase winding current (15) are at the predetermined ratio, and when the phase position of the intrinsic induction (16, 17) lags that of the phase winding current (15) with respect to this ratio, the variable (V, F) supplied to the converter (10) is produced such that the converter reduces the frequency supplied to the motor in the next control interval and/or increases the voltage supplied to the motor in the next control interval, until the phase positions of the intrinsic induction (16, 17) and of the phase winding current (15) are at this predetermined ratio.
- 11. A device for controlling a voltage/frequency converter controlled single or polyphase electric motor (PM) with a voltage/frequency converter (10) which supplies to each motor phase winding (1, 2, 3) an alternating voltage with a frequency fixed per control interval and with a control means (21) which supplies to the converter (10) a variable which corresponds to the induced voltage in at least one motor phase winding (1, 2, 3), for the frequency and/or voltage control, characterized by at least one measuring means (20) for acquiring the current flowing in a motor phase winding and an evaluation means which is connected to the control means (21) and which is set up to evaluate whether the phase position of the intrinsic induction (16, 17) is at a predetermined ratio or not to that of the phase winding current (15) of the same motor phase winding or not and which supplies a corresponding evaluation signal to the control means (12), wherein the control means, when the evaluation signal indicates to the evaluation means that the ratio of the phase position in each case of the intrinsic induction (16, 17) and of the phase winding current (15) does not correspond to the predetermined ratio, with a phase of the intrinsic induction (17) which leads with respect to this ratio, to the converter (10) supplies a control signal which effects a frequency increase and/or voltage reduction in the next control interval until the phase positions of the intrinsic induction (16, 17) and of the winding phase current (15) are at the predetermined ratio and with a phase of the intrinsic induction (16) which lags with respect to this predetermined ratio, to the converter (10) supplies a control signal which effects a frequency reduction and/or voltage increase in the next control interval until the phase positions of the intrinsic induction (16, 17) and of the phase winding current (10) are at the predetermined ratio or lie in previously fixed limits.
Specification