Apparatus for controlling power transducers of the pulse width modulation (PWM) control type

Claim 1

An apparatus for controlling a power transducer capable of converting DC power into three phase AC power and/or vice versa by means of a pulse width modulation (PWM) control, having a processing unit for producing gate signals which turn on and off switching elements of the power transducer, said processing unit comprising: memory means including a first area for storing data of events, according to which the on or off states of the respective switching elements are determined, the combination of three different events determining an operational mode of the power transducer, said operational mode being defined by dividing one cycle of voltage or current of the three phase AC power into six; said memory storing means including also a second area for storing data of enabling times with respect to predetermined phase angles of the voltage or current of the three phase AC power, at which enabling times a constant timer interruption interval of said processing unit is divided into three subdivided intervals in proportion to the magnitudes of the voltage or current of the respective phases of the three phase AC power and corresponding events are enabled; processing means adapted so as to execute, for every timer interruption interval, a step of calculating a composite phase angle on the basis of at least a frequency or frequency instruction of the three phase AC power, a step of determining one of the operational modes in accordance with the calculated composite phase angle; and a step of reading out three events belonging to the determined mode and corresponding enabling times by retrieving said memory means in accordance with the calculted composite phase angle and the determined operational mode; and output control means, including a timer, for selecting one of the read-out events every time when the timer indicates a time coincident with an enabling time accompanied with an event to be selected to thereby produce the gate signals of the switching elements in accordance with the content of the selected event at the time of the corresponding enabling time.

Claim 2

An apparatus for controlling a power transducer capable of converting DC power into three phase AC power and/or vice versa by means of a pulse width modulation (PWM) control, having a processing unit for producing gate signals which turn on and off switching elements of the power transducer, said processing unit comprising: memory means including a first area for storing data of events, according to which the on or off states of the respective switching elements are determined, the combination of three different events determining an operational mode of the power transducer, said operational mode being defined by dividing one cycle of voltage or current of the three phase AC power into six; said memory storing means including also a second area for storing data of enabling times with respect to predetermined phase angles of the voltage or current of the three phase AC power, at which enabling times a constant timer interruption interval of said processing unit is divided into three subdivided intervals in proportion to the magnitudes of the voltage or current of the respective phases of the three phase AC power and corresponding events are enabled; processing means adapted so as to execute, for every timer interruption interval, a step of calculating a composite phase angle on the basis of at least a frequency or frequency instruction of the three phase AC power, a step of determining one of the operational modes in accordance with the calculated composite phase angle; and a step of reading out three events belonging to the determined mode and corresponding enabling times by retrieving said memory means in accordance with the calculted composite phase angle and the determined operational mode; and output control means, including a timer, for selecting one of the read-out events every time when the timer indicates a time coincident with an enabling time accompanied with an event to be selected to thereby produce the gate signals of the switching elements in accordance with the content of the selected event at the time of the corresponding enabling time.