Single-speed drives start motors abruptly, subjecting the motor to high torque and current surges up to 10 times the full-load current. Variable frequency drives offer a soft start, gradually ramping up a motor to operating speed. VFD minimizes the mechanical and electrical stress on the motors and can reduce maintenance and repair costs and extend the motor life.
Energy savings from variable-frequency drives can be significant. For example with centrifugal fan even a small reduction in motor speed can reduce fans energy use by as much as 50%. For example a 25 hp motor running 23 hours per day (2 hours at 100% speed; 8 hours at 75%: 8 hours at 67%; and 5 hours at 50%) a variable frequency drives can reduce energy use by 45%. Because benefits vary depending on operating speed of the system hence it is important to calculate benefits for each application before specifying a variable frequency drive.
In Solapur Textile Cluster units, the doubling machine motor is operated at constant speed irrespective of the requirement. As the speed is varied as per the spindle speed requirement by optimizing the motor speed will reduce the power consumption per kg of yarn processed.
Considering the above facts and for reducing electricity consumption in the doubling machines, it is suggested to install VFD for doubling machines. The details power consumption of various doubling machines and specific power consumption per kg of yarn is furnished
Programming of VFD :
Depending on the model a VFD’s operating parameters can be programmed via: dedicated programming software, internal keypad, external keypad, or SD card. VFDs will often block out most programming changes while running.
Typical parameters that need to be set include: motor nameplate information, speed reference source, and braking control.
It is also common for VFDs to provide debugging information such as fault codes and the states of the input signals.
Most VFDs allow auto-starting to be enabled. Which will drive the output to a designated frequency after a power cycle, or after a fault has been cleared, or after the emergency stop signal has been restored (generally emergency stops are active low logic). One popular way to control a VFD is to enable auto-start and place L1, L2, and L3 into a contactor. Powering on the contactor thus turns on the drive and has it output to a designated speed. Depending on the sophistication of the drive multiple auto-starting behavior can be developed e.g. the drive auto-starts on power up but does not auto-start from clearing an emergency stop until a reset has been cycle