In the working process of a single-phase variable-frequency power supply, the control circuit is in effect. What is the structure of the control circuit of the single-phase variable-frequency power supply? The experts of Instrument World World Network below will introduce the control system of single-phase variable frequency power supply.
The control circuit mainly includes the control power supply, SA866-based SPWM wave generator, isolation drive and protection circuit.
The DC voltage obtained by rectifying and filtering the 220V AC power is used as the input of the inverter DC voltage of the PS21255, and the SA866 generates three mutual differences 120. The three pairs of SPWM signals, through the photoelectric isolation effect on the PS21255 control input, the output of the PS21255 outputs three SPWM waves with a mutual difference of 120 to drive the asynchronous motor. By changing the output frequency, asynchronous motor speed control can be realized.
The PS21255 has overheating, over (under)voltage, overcurrent and overtemperature detection and protection circuitry. When any kind of fault occurs, it will block the internal 6 IGBTs and send the fault signal FO.
Control power supply using 7805 and 7815 to provide DC power supply.
SA866AE can achieve continuous adjustment of speed and forward and reverse switching through 10-bit digital-analog converter and external positive and negative direction pins.
SA866 work in mode N3, set the frequency through the external circuit to achieve SETPOINT, RACC, RDEC and the corresponding circuit to achieve the frequency of acceleration and deceleration, SERIAL end vacant. All operating parameters, including carrier frequency, waveform, minimum pulse width, dead-band pulse width, and V/f curve are programmed through an external EEPROM.
The system adopts the external EEPROM mode, EEPROM selects AT93LC46 that Atmel Company produces, it only needs +5V voltage to work, can write and erase 106 times repeatedly. The chip's package is DIP-8, where Vcc and Vss are the positive and negative sides of the 5V power input, CLK is the clock signal input, DI is the data input, DO is the data output, and ORG is the internal data storage structure. An 8-bit or 16-bit selection is possible. The corresponding pins are connected to the SDA, CS, and SCL pins of the SA866AE.
The above is the introduction of the related knowledge of the control system of the single-phase variable-frequency power supply. Everybody can conduct in-depth research on this control system.
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