Abstract
The GTR VVVF is a kind of cheap practically way, the usage in variously electromotive device will be more and more extensive, as a result it has good market foreground.
In this paper，a GTR VVVF system controlled by mcu is described.Main circuit adopts VD as UR, and at the same time vary the voltage and frequency with PWM inverter. and with GTR we can compose AC-DC-AC VSC (voltage source converter). And it controls in the way of constant voltage against constant frequency .The cores of the control circuit is AT89C51，which depends on the keyboard to give the setting frequency values，then comparing the values with the back values. With the VM(voltage modulator),the current modulator can give signals to three-phase programmed SPWM modulate wave integrated chip HEF4752V，it produces 2-5Kz control signal to let GTR on or off .that is to say ,its sine wave can be adjusted.Thus by changing voltage and frequency ,we can get very real and changeable. In order to make the system work stably ,in this design, It counts and examine rotational speed through photo electricity. it sends processor to carry on corresponding adjustment .
As a series soft and hardware design, it can satisfy the system design request.But because of the restriction of chip HEF4752, this design only can be applicable to some medium and low system, this is a certain of restriction at application of catholicity .
The design has given out the overall plan of the system，the control strategy and realization of the hardware，software，data calculation，the choice principle of the product type and procedure codes.
Keywords：SPWM；inverter；mcu；AC speed adjustment system
