VFD Drives Manufacturers - VFD
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For too long, the importance of grounding to protect motor bearings has been underestimated. To minimize harmful currents and realize the full & quot;green& quot; potential of variable frequency drives, an economical, long-term method of shaft grounding is a must. Until all OEM motors marketed for use with variable frequency drives are truly & quot;inverter-ready& quot; retrofitting them with shaft grounding is the best approach.
In theory, because this grease contains conductive particles, it would provide a lower-impedance path through the bearing and would bleed off shaft current through the bearing without the damaging discharge. Unfortunately, the conductive particles in these lubricants increase mechanical wear to the bearing, rendering the lubricants ineffective and often causing premature failures. This method has been widely abandoned as a viable solution to bearing currents.
Line Termination Network (LTN) near Motor: The LTN is a NEMA 4X device mounted near the motor. The LTN theory of operation is based on transmission line analysis. The LTN passive network elements closely match the cable surge impedance so that voltage reflection is eliminated. A single LTN is possible for the entire hp range from 2 to 500 hp since bundled cable surge impedance only marginally changes from #18 awg to 500 MCM and motor surge impedance is always much greater than cable impedance. Motor terminal voltage is not sloped off but has the same risetime to the Vbus level as the VFD output risetime. However, peak motor terminal voltage is usually less than 1.2 pu as shown in Fig. 4. Terminator waveform plots in Fig. 5 and 6 show the reflected wave peak voltage minimized for a single PWM pulse sent from the VFD manufacturer. The LTN will limit peak voltage at 600 ft of cable to 780 Vpk on a 480 V system and 960 Vpk on a 575 V system. Both values are safe values within the motor 1,000 Vpk at 0.1 us capability
Variable frequency drive
Address: Galaxywind Building, No. 5 Xinxi Road, North Area High-tech Industrial Park, Nanshan, Shenzhen, Guangdong, China, 518000
Tel: 0086-139-28480241
We have more than 10 years practical experience in VFD drives producing in Shenzhen China.
VFD drives, also known as ac drives and VFDs, are widely used in HVAC systems, pumps and conveyors. An ac drive controls the rotational speed of an electric alternating current (AC) motor by adjusting both voltage and frequency of the electrical power supplied to the ac motor.
The efficient way of cutting down the electricity cost on these motors is to adjust the frequency or speed of operation for the ac motor when big power AC motor is being used. It is the general purpose of the variable frequency drives (VFD) being used for. Electric motors that do not adjust their frequency are limited to operate at the maximum frequency all the times, even when not so much power demand. The ability to adjust the frequency when less power is needed, and also can achieve full power running of the motor can improve efficiency, electricity savings, and optimize the motor-driven process. The energy savings from a frequency inverter can be dramatic, with common energy savings of fifty percent or more. Another advantage of using variable frequency drive is their ability to extend the speed range of the ac motor by being able to have adjustable frequency up to 4000 Hz rather than the normal maximum of 50/60 Hz. However, operation of motors at speeds above their rated operating speeds must be checked and approved by the motor manufacturer. Most ac drives are often programmable and allow the operator to select the conditions that are most suitable for their particular application.
