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I was in a medium course for the whole of last week and the trainer mentioned that SF6 filled-switchgear is by far the safest compared to vacuum and air filled. But he could not explain to us why the gas is so good in quenching a flash. I did not need a...

Great infor

Thankyou ScottyUK for the information.I have forgoten what ACB is. AutoCB,ArmatureCB? Sorry for a stupid question..?

Thanks scottyUK. He feels that the purpose of 80A fuses will be to protect the whole installation i.e. cable, motor and VSD. This is also good for discrimination purposes between the breaker and the CB. But this argument is very crude especially considering jraef's comment. Installing correctly...

Thanks a lot for the replies.

Thank you jraef and sed2developer for your valuable advice. Jraef, you sound surprised that I have both fuses and CB? I have seen a couple of installation done that way especially if the supply comes from a far source. I thought I may escape the trouble of replacing the old 80A isolating-fuses...

I am doing a motor control upgrade. The present installation is as follows:- · 400V, 15 KW, 2pole, 3Ph sq-cage induction motor spinning a high inertia fan. · Cable from sub-station isolating fuses to the starter and then the motor 6mm sq – a distance of 18 meters · Fuse rating 80 A ·...

Thank you for the comments. These guys know the procedures and they have been trained over and over again but sometimes proper work ethics fall through the cracks and this can be disastrous. One stupid action can easily jeopardise the plant or people’s lives. In this particular incident no one...

I wish to share some learning with you guys about this failure.It sounds basic but it may help someone. A week did not go by after posting a question on thread237-176733 about an upgrade I am intending to do of a 40 years old system. An operator and a mechanical fitter were changing over fans...

Thank you all for the good suggestions and assistance. I will surely give you an update after installation in May. God bless

Thanks Skogsgurra and itsmoked for the worthy replies. Itsmoked, idea of a new fan is non-stater option because of how complex the ducting system is and the time it will take to do that. We can't have this system OFF for too long thats why we have two - one on stand-by. Skogsgurra:- I am not...

I kindly need your input on a project I am doing, pardon me for the long text. I have 2 furnaces with a common fume-extraction-duct. The duct split in to two (like a ‘Y’) and a fan is fitted on each split for the purpose of redundancy. The fans sit in the ducts but shafts, mechanical torque...

Sorry for this. I rushed to posted a suggestion without reading CJCPE's post, he had mentioned the same point earlier.

Lateral thinking: - My concern about adapting the protection of 250Hp motor to that of 200HP is that years to come new electricians and engineers will replace the current crew. For some reason the load requirements might increase and a need for motor upgrade will surface. They guys will look at...

'Provide high power (2 hp) / torque at low or 0 rpm' For interest sake, why is your application needing 2HP torque at zero rpms.

*"You'll have a probable concern about your motor winding when it is not an INVERTER SPIKE resistance duty". *"Please consider using the new shielded inverter lead cable that is available". This is new to me. I am currently doing two upgrades and I have surely not put these two factors into...

Quote from Rocketir(3 Aug 06 11:04):- '..... The only difference is the impedances' My question about the impedance was triggered by Rocketir’s post otherwise I was not confused. We are all on the same page now. Thanks to you all for the valid posts and contributions. I am glad it’s all...

I need to go sleep and try to consolidate all the obove fair answers tomorrow morning.... I am on +2GMT. Once again thankyou everyone. And for those who still want to contribute you are welcome. Bestboy

sorry I missed some replies before sending my 2nd question. Forgive me

Thanks gents for the quick reply. I am seeing the light now. However I have some questions: - 1stThe impedance we are talking about is it line impedance or load. Because I hear that in normal fault analyses you ignore the load impedance? The faults I am referring to are ones that may happen...