Method of controlling pulse width modulated inverter for use in induction motor drive

Claim 2

A control method of a pulse width modulated inverter for driving an induction motor in a speed variable manner, utilizing a process for forming a pulse width modulating signal by a microcomputer comprising the steps of: (a) executing a command for reading a value of a rated frequency (f 1 )max externally set; (b) calculating the number of running pulses for calculating the number N of pulses allotted to a half cycle of a modulating wave corresponding to the running frequency f 1 from a zero frequency to said running frequency f 1 ; (c) calculating a PWM timer fundamental unit time t for determining a fundamental unit time of a carrier wave; (d) calculating a crest value H wherein H=1/(4t×N×f 1 ) of said carrier wave; (e) calculating a voltage V 1 wherein V 1 =βf 1 and β is a constant; (f) calculating an amplitude ratio K H corresponding to said voltage V 1 ; (g) calculating a modulating wave level D wherein D=K H ·H; (h) calculating data for determining the carrier waveform by the use of said PWM timer fundamental unit time t and said crest value H; (i) calculating data for determining the modulating waveform by the use of said modulating wave level D; and (j) forming said pulse width modulating signal by the use of said data for determining the carrier waveform and said data for determining the modulating waveform.

Claim 3

A control method of a pulse width modulated inverter for automatically adjusting an output voltage from said inverter, utilizing a process for forming a pulse width modulating signal by a microcomputer comprising the steps of: (a) executing a first command for reading a value of a rated frequency (f 1 )max externally set; (b) calculating the number of running pulses for calculating the number N of pulses allotted to a half cycle of a modulating wave corresponding to a running frequency f 1 from a zero frequency to said rated frequency; (c) calculating a PWM timer fundamental unit time t for determining a fundamental unit time of a carrier wave; (d) calculating a crest value H wherein H=1/(4t×N×f 1 ) of said carrier wave; (e) calculating a voltage V 1 wherein V=βf 1 and β is a constant; (f) calculating an amplitude ratio K H corresponding to said voltage V 1 ; (g) executing a second command for reading out an average voltage Vav obtained by rectifying the output signal from said inverter; (h) calculating an amplitude ratio K' H corresponding to said average voltage Vav; (i) calculating a difference ΔK H between said amplitude ratios K' H and K H ; (j) calculating an amplitude ratio (K H ) 1 corresponding to said difference ΔK H ; (k) calculating a modulating wave level D-(K H ) 1 ·H; (l) calculating data for determining the carrier waveform by the use of said PWM timer fundamental unit time t and said crest value H; (m) calculating data for determining the modulating waveform by the use of said modulating wave level D; and (n) forming said pulse width modulating signal by the use of said data for determining the carrier waveform and said data for determining the modulating waveform.

Claim 4

A control method of a pulse width modulated inverter for automatically adjusting an output voltage from said inverter, utilizing a process for forming a pulse width modulating signal by a microcomputer comprising the steps of: (a) executing a first command for reading a value of a rated frequency (f 1 )max externally set; (b) calculating the number of running pulses for calculating the number N of pulses allotted to a half cycle of a modulating wave corresponding to a running frequency f 1 from a zero frequency to said rated frequency; (c) calculating a PWM timer fundamental unit time t for determining a fundamental unit time of a carrier wave; (d) calculating a crest value H wherein H=1/(4t×N×f 1 ) of said carrier wave; (e) calculating a voltage V 1 wherein V=βf 1 and β is a constant; (f) calculating an amplitude ratio K H corresponding to said voltage V 1 ; (g) executing a second command for reading out an average voltage Vav obtained by rectifying the output signal from said inverter; (h) calculating an amplitude ratio K' H corresponding to said average voltage Vav; (i) calculating a difference ΔK H between said amplitude ratios K' H and K H ; (j) calculating an amplitude ratio (K H ) 1 corresponding to said difference ΔK H ; (k) calculating a modulating wave level D-(K H ) 1 ·H; (l) calculating data for determining the carrier waveform by the use of said PWM timer fundamental unit time t and said crest value H; (m) calculating data for determining the modulating waveform by the use of said modulating wave level D; and (n) forming said pulse width modulating signal by the use of said data for determining the carrier waveform and said data for determining the modulating waveform.

Claim 5

A control method of a pulse width modulated inverter for automatically calculating the output current from said inverter, utilizing a process for forming a pulse width modulating signal by a microcomputer comprising the steps of: (a) executing a first command for reading a value of a rated frequency (f 1 )max externally set; (b) calculating the number of running pulses for calculating the number N of pulses allotted to the half cycle of a modulating wave corresponding to a running frequency f 1 from a zero frequency to said rated frequency; (c) calculating a PWM timer fundamental unit time t for determining a fundamental unit time of a carrier wave; (d) calculating a crest value H=1/(4t×N×f 1 ) of said carrier wave; (e) calculating a voltage V 1 wherein V 1 =βf 1 and β is a constant; (f) calculating an amplitude ratio K H corresponding to said voltage V 1 ; (g) executing a second command for reading an average current Iav obtained by rectifying the output current from said inverter; (h) calculating an amplitude ratio K" H corresponding to said average current Iav; (i) calculating a difference ΔK' H between said amplitude ratios K" H and K H ; and (j) calculating an amplitude ratio (K H ) 2 corresponding to said difference ΔK H '; (k) calculating a modulating wave level D wherein D-(K H ) 2 ·H; (l) calculating data for determining the carrier waveform by the use of said PWM timer fundamental unit time t and said crest value H; (m) calculating data for determining the modulating waveform by the use of said modulating wave level D; and (n) forming said pulse width modulating signal by the use of said data for determining the carrier waveform and said data for determining the modulating waveform.

Claim 6

A control method of a pulse width modulated inverter for automatically calculating the output current from said inverter, utilizing a process for forming a pulse width modulating signal by a microcomputer comprising the steps of: (a) executing a first command for reading a value of a rated frequency (f 1 )max externally set; (b) calculating the number of running pulses for calculating the number N of pulses allotted to the half cycle of a modulating wave corresponding to a running frequency f 1 from a zero frequency to said rated frequency; (c) calculating a PWM timer fundamental unit time t for determining a fundamental unit time of a carrier wave; (d) calculating a crest value H=1/(4t×N×f 1 ) of said carrier wave; (e) calculating a voltage V 1 wherein V 1 =βf 1 and β is a constant; (f) calculating an amplitude ratio K H corresponding to said voltage V 1 ; (g) executing a second command for reading an average current Iav obtained by rectifying the output current from said inverter; (h) calculating an amplitude ratio K" H corresponding to said average current Iav; (i) calculating a difference ΔK' H between said amplitude ratios K" H and K H ; and (j) calculating an amplitude ratio (K H ) 2 corresponding to said difference ΔK H '; (k) calculating a modulating wave level D wherein D-(K H ) 2 ·H; (l) calculating data for determining the carrier waveform by the use of said PWM timer fundamental unit time t and said crest value H; (m) calculating data for determining the modulating waveform by the use of said modulating wave level D; and (n) forming said pulse width modulating signal by the use of said data for determining the carrier waveform and said data for determining the modulating waveform.