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  1. Ants

    Phase rotation and synchr testing of remote sources

    I currently have the enviable opportunity to supply my manufacturing plant with more than one electrical source for backup purposes. Essential to this is both phase rotation and synchronisation as a fast transfer must be initiated. I am looking for a method of comparing these, taking into...
  2. Ants

    Large motors preservation in stores/wharehouse

    We are in the process of building a new plant, and as things go some equipment arrive very early and some very late. My concern lies with the preservation of rotating as well as non-rotating equipment. Firstly, large (and other sizes) motors needs to be on space heaters (if facility is provided...
  3. Ants

    MTBF Degradation of CPU's After Sustained Overtemp

    Hi, I've been walking around with a question in my head and after seeing this thread thought to ask it here. Apart from abnormal conditions - high temperature etc..- does electronic equipment age?? Or is aging just the accumulated effect of say overtemps, spikes, surges etc.. Is 'ageing' and...
  4. Ants

    Medium voltage captive transformer specification

    Good day gentlemen! I am currently investigation the possibilty of upgrading a 5 MW 6600V 3phase motor to about 6.2MW (not yet standard size). My problem is that it feeds from a captive transformer (is this term used worldwide?) rated 8MVA and 33kV / 6.6 KV , 4.07% impedance at 33kV. What is the...
  5. Ants

    standard CT's and VFD's

    Thanks Electricpete, valid remarks. I omitted to say that these measurements were taken at full speed(50 Hz, 1490rpm) and full voltage applied to the motor terminals (525 volt on both drive input and output, 3 phase). I believe the load measured on the output side of the VFD is the correct one...
  6. Ants

    standard CT's and VFD's

    Hi Guys, this has made for some interesting reading, and triggered something which I noticed recently. I have about 230 VFD's (525V, 50Hz)in my plant, and we are doing our own repairs and fault finding (not relying on supplier contracts etc..) Now although we have become quite good at it, some...
  7. Ants

    Variable Frequency Drives: failures & contamination

    I work for a chemical plant with an inherently corrosive atmosphere. I have a large base of new technology (4 years oldest)VFD's. Over the past year we experienced an abnormally high rate of failures, mostly related no non-power elements (gate driver boards, rectifier drives boards comms cards...

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