1467 / 2440
20-60 Edition 47
Longwall
Variable Frequency Drives
Features
Air-Cooled VFD Container
Liquid-Cooled VFD Container
The application of VFD brings a significant improve-
ment for the plow and AFC operation. It implements
among others the following advantages:
●
High Power System Stability/Quality
– Application of standard asynchronous motors.
– Distance between motors and powering VFDs up
to 4 kilometers (2.4 miles).
– The usage of “weaker” networks is possible.
●
No EMC-Effects
– Du/Dt is small, no special requirements to motor’s
insulate performance.
– No overvoltages and reflection waves.
– No high-frequency interference by pulsing circuit
of IGBT.
– No network perturbations by large harmonic wave
components.
– No parasitic ground currents.
●
Variability/Dynamic of the Drive System
– Variable speed for AFC and plow in a wide range
(0 to 120% of nominal speed).
– Greater dynamic of drive system.
– Unlimited start-ups of the motors.
– No significant voltage drop during start-ups.
– Reduction of mechanical stress.
●
Synchronicity and Precision/Utilization of the Full Power
– High constant torque throughout the entire speed
range from 0 to maximum speed.
– Full utilization of installed power on both plow’s
motors through load shearing.
– Synchronized start-up of all drives at full load.
– Controlled load distribution between all drives.
– Torque control function makes motor work with
constant torque.
– External encoder interface for speed feedback.
– Moment and speed parameterizable.
●
Low Life Cycle Costs
– Reduction of impact of drive system on chain, line
pans and chain sprockets.
– Quick torque and speed reduction in case of block-
ades or chain cracks.
– Improvement of overload protection for motors and
chains.
– Detection of chain break through controlled shut down.
●
Energy Recovery
– Breaking possibilities and thus returning power back
to the network.
●
Maximum Torque at Zero Speed
– Total torque control at zero speed.
– Tension of the chain without a chain tensioning unit.
●
Monitoring System
– System parameter (voltage, power, torque, effective
power, speed, etc.) are directly (online) available.
●
Optional Functions
– Evenly distributed load of conveyor by adjustment
of speed depending on the direction of motion of
the extraction machine (optional).
– Adjustment of profit performance depending on
capacity utilization of downstream systems (optional).
Variable Frequency Drives (VFD)
●
Features