Zilsel Invent Blogspot

This article is dedicated to the frequency modulation of the VF driver. The article presents different ways to change frequency in run-time . Also, we will see the difference between ideal and real frequency equation as well as the difference between ideal and real components. Frequency modulation VF driver stands for variable frequency in terms that signal frequency can be changed in runtime. It is a signal modulation since frequency is changed during runtime mode, but common term is variable frequency driver. It is very important to have a square wave generator with possibility to modulate the signal frequency. Why? Because different loads can work with different frequency. In this case load is a DC motor, which means that different DC motors works on different frequencies. Some DC motors work at lower frequencies, other DC motors work on higher frequencies, and that is the reason why it is important to have VF driver – to search and find the appropriate frequency of th...

The Figure #1 presents basic astable multivibrator circuit. This is the basis used for many different applications like: capacitance measurement circuit used for the digital multimeters (in some digital multimeters implementations), free running square-wave signal generator, free running triangular signal generator and the variable frequency drivers (VF Driver). In this case, this circuit is basis for the variable frequency driver, used to drive the DC motor controllers with the pulse width modulation (PWM) capabilities in order to provide DC motor torque and speed regulation .   General discussion The circuit (Figure #1) is consisted of the two main parts: the integrator and the comparator with the hysteresis. The comparator with the hysteresis is built around the operational amplifier: OpAmp (2), resistor R2, resistor R3 and the reference voltage defined by the position of the potentiometer P1. The resistor R3 is the feedback resistor and it is used to feedback current sta...