Caterpillar Performance Handbook, January 2017, SEBD0351-47

Variable Frequency Drives (VFD) ● Features

Longwall

● 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 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.

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