HMI and PLC Program for Variable Frequency Drive Set point

A variable frequency drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply. The VFD also has the capacity to control ramp-up and ramp-down of the motor during start or stop, respectively. Even though the drive controls the frequency and voltage of power supplied to the motor, we often refer to this as speed control, since the result is an adjustment of motor speed. There are many reasons why we may want to adjust this motor speed.  For example, to Save energy and improve system efficiency Convert power in hybridization applications Match the speed of the drive to the process requirements Match the torque or power of a drive to the process requirements Improve the working environment Lower noise levels, for example from fans and pumps Reduce mechanical stress on machines to extend their lifetime Shave peak consumption to avoid peak-demand prices and reduce the motor size required In addition, today’s drives integrate networking and diagnostic capabilities to better control performance and increase productivity. So, energy savings, intelligent motor control and reduction of peak-current drawn are three great reasons to choose a VFD as the controller in every motor-driven system. The most common uses of a VFD are for control of fans, pumps and compressors, and these applications account for 75% of all drives operating globally. Soft starters and across-the-line contactors are other, less sophisticated types of motor controllers. A soft starter is a solid-state device and provides a gentle ramp-up to full speed during startup of an electric motor. An across-the-line contactor is a type of motor controller that applies the full line voltage to an electric motor. Three-phase induction motors operated on line voltage have relatively smooth sine waves with a 50- or 60-hertz (Hz) frequency, depending on the location. For two-pole motors, this equates to a 3,000- or 3,600-rotations per minute (rpm) synchronous pole speed. Without a VFD, the speed of the motor is relatively constant and changes minimally as a function of load due to motor slip. With a VFD, voltage and current fed to the motor are controlled by turning on and off insulated-gate bipolar transistors (IGBTs). The amplitude of the voltage and current values is controlled by the frequency of the switching and on and off time of the IGBTs. This means the longer the switches are on compared to the time they are off, the larger the voltage and current values.  Pulse width modulation (PWM) is a high-frequency waveform generated by the IGBTs to simulate a sine waveform to the motor. The frequency of the sine wave can be varied by the VFD, resulting in a change in motor speed. PWM is advantageous because the power loss in the switching devices is low, resulting in relatively high efficiency and energy benefits when considering the reduced hydraulic power at lower speeds. With the power being switched on and off rapidly, the resulting power waveform closely approximates the average current and voltage that a utility power source would normally supply a motor (sine wave). In this lesson, i will making HMI and PLC Program for variable frequency drive VFD Set point. #variablefrequencydrive #plcprogramming #inductionmotor