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I have had some practical experience with the Mirus product and in practice have achieved THDI figures of 5,3 to 6% in an average Industrial installation. This is similar to that achieved by an 18pulse drive . No, it is not just a Zig Zag transformer and for those who want an explanation of...

Marke is 100% correct and this type of fault is probably more easily seen if you are using an old analogue Ammeter to display the current . There will be a noticeable kick in the current reading with every revolution of the machine .

Just another point regarding Markes comments , surely the thyristor is "off" at the end of every half cycle . Of course the Contactor will isolate the starter from mains borne transients when the starter is non operational but at other times , it is exposed.

GGOSS , I was not in any way trying to knock anyones product , nor was I trying to suggest that Inside Delta should never be used in any circumstance . I was expressing a personal opinion based on some unexplained occurences . The Softstarters I refer to were also robust and well designed but...

GGOSS I have always been wary of inside delta on large machines . Some years ago I had a few spectacular thyristor failures and flashovers similar to those you describe....funnily enough , at least two of the starters were on compressors. One thing to remember is that the thyristor 'sees'line...

Some critical info is missing Mishlove . Some good advice has been given already but I would make the following comments: The THDI that you quote is certainly on the INput of the drive . That figure would have no effect on what is happening on the Motor side anyway . Measuring the Motor side...

""Just out of curiosity, how much additional heat (percentage) do you think that VFDs output harmonics contribute to the motor; "" Depending on your VVVF drive design , the Motor may run cooler with the VVVF supply than on the mains . Differences of a degree or so in favour...

Firstly work out what speed will give you 25%load. As outlined above , kW falls as per the cube of the speed . If your motor draws full load at full speed ....then 25% load should be somewhere around 63%speed Then (when the Generator kicks in) you need to switch the speed reference from the...

I read the section in the AB manual yesterday . It sounded as though it was something that they had put into the software just in case a prospective purchaser compared them unfavourably with someone that had it . Lets be fair , many starters have the feature ..........but NONE of the...

Farkel , If I assume that you have a seperate cable feeding each Motor , then your poor VSD is 'seeing' 15 x 150 feet of cable . Sounds like you have about 700 meters of cable on this poor little VSD . I am suprised that the customer even gets these motors to start. First step should be to...

If more than approx 30% of the VA rating of a generator goes into 6 pulse drives then there is a distinct possibilty that the Damper windings will overheat and damage . The Damper windings are there to help in damping torque pulsations from the Genset . There is / was a regulation which I...

When you refer to Power Factor, are you talking about TOTAL Power factor or displacement Power factor?? On a standard VVVF there is or can be a big difference between the two....i dont know your reasoning behind asking the question but it may be worth following through .

It may well be my imagination but I get the feeling that some of these posts are cleverly disguised product promotions. It would be nice if these guys would drop the act and give us some hard evidence that these devices work and actually save a substantial amount of energy in the average...

The soft start is not intended for the full voltage across the motor terminal even though the softstarter manufacturer may provide the softstart output capable of the full voltage across the motor terminal start I am not too sure that I understand you correctly JBartos .........some Soft...

GGOSS , I would love to have a look at what you have done . send it to me at freo2001au@yahoo.com.au thanks . Harry

Thanks for the input guys and Hi to Marke and Mr Goss . BTW Marke I could not follow your links ........something to do with bandwith being exceeded. What I was hoping for was a nice article , clearly written with all the pros and cons laid out . I have a copy of AS 3947 in front of me as I...

Can anyone point me to any papers on the rating of soft starters according to IEC or similar ? It seems to be a bit of a mine field with some manufacturers offering 5 times current for 30 seconds , 10 times per hour ...........and some offering 3 times for 10 seconds , 6 times per hour...