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Hi Engineers, I am looking for guidance on selection of Low Voltage Drives on the basis of: 1.Dimensioning- torque,overloadability 2.Performance- V/f control, sensorless vector control,closed loopp vector control,static & dynamic accuracy of speed & torque, respose time Searching threads...

Motor size classification is getting confusing. Some vendors are following Size classification other than the NEMA standard. Could you please help me with any information regarding correlation beetween the different size classifications?

Hi, I got a smoother waveform with notches of shorter time period which is considered within the 25%percent overload capacity of the rectifier. I guess the answer to my question belongs to some other aspect of the crane design - its gross nature!

Hi, [tab]Your conclusions are absolutely correct Gunnar Englund. The waveforms that I got were similar in four of my cranes having rectifier drives. Special Thanks Gunnar But does it hold true for the rectifiers which supply dc to the dc bus common to three drives? Because in this case the...

Hi All, [tab]It has become a great topic due to your super contribution. Kudos to you all. There is a flaw in my explanation that has caused you some confusion. EXTREMELY SORRY skogsgurra, scottyuk and sed2developer [tab]The rectifier gets 3-Phase AC supply from the alternator(DGset). The...

I have MX321 AVR in my genset and it is the best I believe. Does the controlled rectifier have very high harmonics? Still that would be included in its overload capacity of 125% isn't it? Still pondering D'man

PLease explain DAvid, the power going to motors through drives. The max power delivered to drive is through rectifier only. So the max power calculated from max rectifier should take care of it. Why does it need to be double?

Hi, This question is baffling me ever since I am working in this crane. This crane lifts containers of max. load 40T. It uses rectifier-drive for control of all motors. The kVA rating of the diesel generator set is 670kVA. CAlculating the max kVA load including all auxillary drives, it comes to...

Edison 123, You are absolutely perfect in this topic. It has worked nicely on one 670 kVA alternator. It took me 11 hrs to get the IR to 4M? from 0.5M? with meggering being done every hour after first 3hrs. This is a first in this company. Accolades for you Thanks from the depth my heart D'man

Two types of alternators are available with us here - 670kVA and 551kVA. The exciter ratings are very close 43V,2.5A and 45V,2.5A. respectively. Further two new ones have arrived with rated output of 505kVA. All the ratings are alike varying 1 or 2 units max. If you require Edison I will...

Dear Edison123, You have explained the process in a very clear way. ACCOLADES for you. One small doubt is that we have got a single phase supply near the place. What are the disadvantages of using that? We have two newer alternators of 505kVA rating but the exciter is shaft mounted with...

Hi, It was a hectic week for me. I have gathered details of the alternator in question. Make: Stamford HCI 1500rpm 670kVA 400/231V 732A 50Hz Exciter Voltage=43V Exciter Current=2.5A It has a DC exciter. The alternator is coupled with a Cummins engine. Thanks D'man

Thats nice Edison, do you run the alternator at full speed or less than that. What method are you using to control the exciter current? The time period given by you is exactly what we desire. D'man

Hi thanks for the input. I had the idea that there must be some rules like the ones followed for transformer heating. OK, I will go by the rule of 10% rated wattage. What to do with the connections of shaft mounted diode rectifier? They have to be isolated isn't it? The IR should actually go...

Hi, With 2 of our alternators down with IR value of 1M? it is a precarious condition for us. Any one of the working alternators gets broken down then it would be disastor. The heating with sodium vapour lamps and heat radiators is proving to be very slow. I need your help with the...

Dear Warros, Sorry for the inevitable delay. Your input is commendable. I actually proposed to disconnect the stator feedback to AVR card and do the meggering again (with stator disconnected from the outgoing ckt). Now, with your input I am rethinking it. Thanks and Regards D'man

Hi, Thanks for the input. In fact the practice of isolation is followed by the engineers here. But in a case under emergency they somehow missed the step isolating the AVR card. BUT no damage occured to the AVR card. D'man

Hi, I am new to alternators and AVR cards. I would like to know the reasons(and consequences) of isolating the AVR card before meggering the alternator.

Ya you are very correct - wiring was the problem. I had a nice workout in testing all the wiring done. The downtime and cost involved are also big. It will go down the company history as a legend. I am going for the fluid level sensor with the same gameplan. But it is proving more difficult due...

Hi, 1.The proximity sensor is a PepperlFuchs make 230Volt sensor with a maximum sensing distance of about 15mm. I have got 10 pieces of these. All show correct result while in workshop but fail in the crane(workplace). 2.The liquid level sensor gives the output to Phoenix miniature relay which...