The function of an AC Drive is to change the speed and torque of an electric motor (AC Motor) used in electro-mechanical drive systems by changing the frequency and voltage of the power supplied to the motor. An AC Drive system, which is also known as a variable-frequency drive (VFD), inverter drive, variable speed drive, and adjustable-frequency drive, mainly performs the speed adjustment of a motor.
AC Drives Applications
The AC Drive system has a variety of applications in different electrical systems. Let’s take a look at some common uses:
AC Drives control the performance of various systems in commercial and industrial applications. They work for bringing the quality improvements of different systems’ speed, acceleration, tension, torque, flow, and pressure.
The advantage of using the drives is that they ramp up the motor to the operating speed gradually, reducing the electrical and mechanical stress on the motor and the driven equipment. On the other hand, fixed-speed load keeps torque and current surge at a high point at the beginning, creating damage risk for the motor and other equipment.
The AC Drives provide the flexibility of tuning the configuration of a system to the most energy-efficient level. They help saving more energy than drives that offer the optimization of individual functions of a system.
AC Drives are most commonly used in compressors, pumps, and fans of HVAC systems. Using them other than any other tool in controlling the output of a fan, pump, or compressor system saves a substantial amount of energy.
AC Drives Working Principle
An AC Drive system converts the frequency of a power network, and thus controls the motor speed in a proportional rate to the frequency. Understating some simple basics of AC Drives will help you figure out their working principle. The procedure consists of:
Rectifier unit. The electrical network connects to the AC drive via a uni- or bi-directional rectifier unit. The AC Drive takes energy from the system and uses it to accelerate and run the motor if the rectifier is unidirectional. In the case of a bidirectional rectifier, the drive supplies energy to the network by taking mechanical rotation energy from the motor.
DC circuit. The DC circuit mainly assists the inverter by storing energy for it from the rectifier.
Inverter unit. It works as a bridge for the transmission of energy from the DC circuit to the motor. It creates the three-phase AC voltage output for the motor, which influences the motors speed aka output of the process. A higher frequency of the output voltage results in a higher speed of the motor.
Benefits of AC Drive System
AC Drives offer various benefits regarding system stress, process control, and energy savings of the motors they control. Some of the advantages are:
- Gradually ramp up the torque and current surge, and thus reducing stress on the tools and machines
- Reduce thermal and mechanical stresses
- Cut the level of noise and vibrations in low load situations
- Secure smooth flow of energy by synchronizing between different parts of the main process
- Control the output of the process as required
- Save energy more than the traditional methods of process control