Variable Frequency Drives VFD

 

      Variable Frequency Drives (AC) help to save electrical energy in mechanical machines. The drive allows to reduce the power consumption using Insulated Gate Bipolar Transistors (IGBT) as switch to control the frequency and voltage of the output power. VFDs are available in the market for variety of mechanical machines. Typically the variable frequency drives are useful in lifts, stamping machines, hoists, cranes, and automation applications in the industries.

LGIS (LG Industrial Systems) is a renowned manufacturer of the VFDs. The LG 1ph Starvert IG series drives suits the industrial and commercial lifts. The drives are compact, have easy installation mounts. Also the drives are suitable for low budget applications where the control panel uses micro-controllers as the processing units.

The drives also give a flexible interface to a number of programmable logic controllers (PLCs) in the market. All you need is a programmed PLC and the communication cable that connects the two electronic devices. Usually the cable is RS485 compatible.

The drive helps to reduce the mechanical jerks because of acceleration at the start and stop of the lift. The change in acceleration is spread over two speeds: low and high. Two proximity sensors limit the physical travel of the lift between the start point and stop point near the halts in this travel. At start,the speed of the lift is slow for about 30% of the travel near the stop point of the lift. The high speed covers the remaining 70% travel.The lift mechanic installs these sensors near the door of the lift.

The interfacing of the drive with the control panel of the lift is easy, three connections for slow speed, fast speed, and brake operation are necessary.Also a common electronic earth connects the drive and the control panel.

The drive connects between the 1ph 220V electrical power supply and the 1ph electrical motor. The drive acts as an electrical switch to control the power supply to machine to achieve different speeds. The drive varies the frequency and voltage of the power supply to the electrical machine, thus increases the torque at starts of the motor. The modified torque gives additional advantage at start of the motor with increased load capacity.