Pulse Width Modulated AC Controller
A number of different types of AC motor controllers are currently in common use as general purpose drives, such as Pulse Width Modulated (PWM), Current Source Input (CSI), and the Load Commutated Inverter (LCI).
Each type of AC controller offers specific benefits and characteristics. The Pulse Width Modulated (PWM) AC Controller has been selected by Fincor Electronics because it offers the best combination of simplicity, performance and economy for general purpose applications.
Below we focus on this type of AC controller - Pulse Width Modulated (PWM) Controllers
The PWM controller converts the AC power source to a fixed DC power by a full-wave rectifier. The DC voltage is smoothed by a filter network and applied to a pulse width modulated (PWM) inverter using high power transistors. The speed reference command is directed to the microprocessor which simultaneously optimizes the carrier (chopping) frequency and inverter output frequency to maintain a proper volts/Hz ratio and high efficiency throughout the normal speed range. See Block Diagram below.
The voltage applied to the motor is a pulsed approximation of a true sinusoidal waveform. It's commonly called a PWM waveform because both the carrier frequency and pulse width is changed (modulated) to change the effective voltage amplitude and frequency. The current waveform very closely follows the shape of a sine wave to provide improved low speed motor performance, efficiency, and minimal motor heating.
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