See full version: How Pulse Width Modulation in a VFD works
In the case of a VFD that utilizes PWM technology, this is done by varying the RMS voltage to the motor. By controlling the amount of time each pulse is on and off, the resulting RMS voltage across the motor phases can be controlled. The ‘width’ of the pulse factors into the resulting RMS voltage output. here
Pulse width modulation uses transistors which switch the DC voltage on and off in a defined sequence to produce the AC output voltage and frequency. Most VFD’s today utilize insulated gate bipolar transistors or IGBT’s. The typical configuration of the IGBT’s in the inverter section of a VFD is shown below in figure 2.
PWM representation with longer “ON” time here
For example, if T1 and T6 are open, current will flow from DC bus positive through the U to V phase of the motor and then to the DC bus negative. If T3 and T4 are open, then current will flow from the DC bus positive through the V to U phase of the motor to the DC bus negative. more
The goal of the PWM control is to create a sine wave current waveform output to produce torque in the motor. more
Since we don’t want to drive the motor directly from the UNO, we will be using an inexpensive little breadboard power supply that plugs right on our breadboard and power it with a 9V 1Amp power supply.
At the same time we will learn how to connect a Rotary Encoder and use it to set the speed and direction.
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In this tutorial we will use a L9110S dual motor driver to control the speed of a small DC Motor.
I.e: *you have to click on the images to see them. here
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There are two pairs of screw terminals on the PWM driver click — one for the external power supply and one for the DC load. [links]
The click contains a P-channel DMP3010LK3 MOSFET transistor. When the click is used for PWM control it is not recommended to use it with loads of wattage over 50W because the MOSFET chip can get overheated; however, this does not apply when the click is used as an ON/OFF switch.
If you need to control DC motors with loads up to 10A, PWM driver click is the perfect solution, thanks to the Silicon Lab Si8711CC one-channel isolator. It communicates with the target MCU over PWM pin, and runs on a 5V power supply. It can be used in a wide variety of ways, from controlling light intensity to serving as an ON/OFF switch to control DC load circuits.
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If you need to control DC motors with loads up to 10A, PWM driver click is the perfect solution, thanks to the Silicon Lab Si8711CC one-channel isolator. more
DC motor speed control, electronic ON/OFF switch for controlling DC load circuits, light intensity control, etc. more
In order to generate a physics-based model of the motor, we need to consider a simplified version of its workings. The following figure represents an electric equivalent circuit of the armature and the free-body diagram of the rotor.
In this activity we will model a simple DC motor for an input of armature voltage and an output of rotational speed. The motor's angular position (and in turn its speed) is determined by a quadrature encoder. The encoder pulses are counted on the Arduino board via two of the board's Digital Inputs (each digital channel can be either an input or an output). The Arduino board is also used for controlling the speed of the motor. Specifically, one of the board's Digital Outputs is employed to switch a transistor on and off, thereby connecting and disconnecting the motor to a DC Voltage source. The Arduino board will also communicate the recorded data to Simulink for visualization and analysis. The logic for estimating the motor's speed based on encoder counts is implemented within Simulink. In Part (b), the logic for controlling the motor's speed will also be implemented in Simulink.
In this experiment, we will employ Simulink to control the motor through the switching of the transistor, to read the encoder output, and to plot the data in real time. In particular, we will employ the IO package from the MathWorks. For details on how to use the IO package, refer to the following link. We will build the Simulink model for this activity in a step-by-step manner in order to explain the nuances of using quadrature encoder output for sensing the motor's speed. more