Recent content by Saut

Metalguy, are there any issues I have to worry if ball bearings are used instead of sleeve bearings. Also, as I'm not very familiar with bearings, I'd like to know if thrust bearings refer strictly to sleeve type bearings or can refer to ball bearings? What does the standard refer to?

ANSI C50.41 states that vertical motors shall have thrust bearings designed to carry all specified axial thrust conditons imposed by driven load. Can contact ball bearings achieve the same function? Is the thrust bearing more advantageous than the ball bearings?

I agree with busbar, there'll be no zero sequence component as your conenction to earth does not result in zero sequence becasue the transformer secondary is delta connected, so you'd be having a single point to earth grounded situation with the currents circulated in the phases, to resolve the...

Thanks for that insight, and that's what I've thought, but I've got quotations from transformer makers that say that the three winding is more expensive than a two winding, due to the manufacturing process and materials, is this true? and they say it also depends on whether is it a high power...

Anyone has any experiences about using glycol as a cooling agent, any hazards and safety standards required?

Anyone got any experiences with 800kVA liquid cooled rectifiers? Are they reliable? Any links to how it looks like and data sheets?

I have a question for costs on power transformers. Would it be cheaper to get two 150MVA Two-winding transformer, or a single 300MVA Three-winding transformer?

Also, I'd like to add that if you don't intend to trend your test results, don't do it. Tan Delta testing, like all other preventive maintenance testing, needs proper trending and records. If you're just concerned about safety during energisation, a megger test is sufficient

Combined cycle plant efficiencies are best shown in heat balance diagrams, which indicate the losses, fuel heat rates, temperatures etc

DC faults are hard to trace especially if there's more than one fault point. Let's assume if there's just one. Then first if you can, isolate all distribution ciruits (positive and negative, confirm that the main batteries are faultless, before tracing each indivual circuits. Alternatively...

Thanks everyone for your responses. I was not specific, I was referring to high currents from the neutral to the ground of DG, at no load, leakage current is 1% and at half load, 5%, seems like leakage current increases with load..does this phenomena confirm that there's a leakage in the stator...

What's the allowable neutral current of a 400V 4-wire DG, solidly grounded? Are there any standards that specify this value?

Thanks plasgears, but what if there's a loss of electrical supply, then wouldn't the electromagnetic type be more dangerous, and what if preventing the leak is not a problem, like minimise the use of joints? Is the industry moving away from hydraulic braking?

I would like to know what is the standard of the braking system on an overhead crane. Some suppliers tell me it's a standard to use electromagnetic braking instead of the conventional hydraulic type. Is this true? and what are the advantages of using the electromagnetic type?

What's the IR after one minute? the standards recommended that if it's more than 10Gohm after a minute, the PI need not hit 2, a 1.5 is good enough. The PI depends on the first minute reads too as short windings saturate faster.