초록 ▼

The inverter includes a low voltage microcontroller referenced to ground potential and a waveform generator coupled to the microcontroller through a serial data link including optical isolation devices. The waveform generator floats at the negative bus potential of the DC source for the inverter. Th

The inverter includes a low voltage microcontroller referenced to ground potential and a waveform generator coupled to the microcontroller through a serial data link including optical isolation devices. The waveform generator floats at the negative bus potential of the DC source for the inverter. The waveform generator produces switching signals for the inverter under control of the microcomputer. The waveform generator, serial communications circuitry and other support circuits are all part of a single application specific integrated circuit. Registers store control parameters from the microcontroller, and counters, a look up table and a state machine derive pulse width modulated switching commands to achieve motor control for a 60°sector of motor field rotation and repeat the derivation of similar switching commands for each subsequent sector. A pulse director applies the pulses to the correct motor phases for a given sector.

대표청구항 ▼

In a control for an inverter for supplying pulse width modulated voltage from a DC bus to a three phase variable frequency induction motor having a microcontroller for determining desired motor operation by outputting frequency, carrier period and duty cycle parameters, and a waveform generator resp

In a control for an inverter for supplying pulse width modulated voltage from a DC bus to a three phase variable frequency induction motor having a microcontroller for determining desired motor operation by outputting frequency, carrier period and duty cycle parameters, and a waveform generator responsive to said parameters for commanding voltage vectors for inverter control, the waveform generator comprising: holding registers for each of the frequency, carrier period and duty cycle parameters; carrier period means responsive to the carrier period parameter for generating a carrier signal at each half period; a look up table containing two sets of sine functions; a state machine for sequentially assuming a plurality of states in each carrier period and for commanding a specific voltage vector for each state, the state machine having an address associated with each state for selecting which set of sine functions to address; means for generating angle values from the frequency parameter, and for addressing the look up table on the basis of the angle value and the state machine address to select a sine value; means responsive to the duty cycle parameter for producing a ramp signal having a slope determined by the duty cycle parameter; comparator means for comparing the ramp signal with the selected sine value to produce a signal when the ramp signal reaches the value of the selected sine value; the state machine including transition means responsive to the comparator means signal and the carrier signal for changing from one state to another, whereby a sequence of voltage vectors are commanded by the state machine at a rate determined by the frequency parameter and each having a duration depending on the selected sine value and the slope of the ramp signal; and means responsive to the means for generating angle values and to the commanded voltage vectors for issuing switching signals to the inverter.