Hi Sakaran,
There is one possible solution that hasn't been discussed, a bit off the wall. How about leave the generator as it is and fit a static frequency converter (VFD). A 3MW drive isn't cheap but it will allow your client to deliver an extra 400kW so may pay for itself in time (;provided...
Hi Mike
The enclosure is aluminium and I assume the gland is brass? The moisture is causing galvanic corrosion between the two materials and aluminium being the anode is corroding. There is a galvanic voltage of 0.5V between the two materials. An aluminium gland would solve this problem if such...
Hi John,
Goof question, and I'm not 100% sure, but normally diff CTs just feed a differential relay and phasing shouldn't matter. But for a multifunction relay, I would imagine they should be ok. If you swap all 6, the phase sequence will be the same.
Hi
A quick check (if you are unable to complete the checks suggested by DTR2011 or Hoxton) would be to swap the CT's between B and C phases. If the 'fault' then swaps to B phase, you know its the CT's, if it stays on A phase then it's either the winding (unlikely from your other checks) or the...
Hi Edison
You don't say why the heat exchanger needs replacing. Assuming it's not a corrosion problem then either material would be ok, I personally would go for the Cu/Ni as it's readily available and relatively inert (90/10 CuNi is specified in the majority of end user specifications. The...
@petronila - thanks for your comments, thats's useful information - they are new coils and this may be a test that some OEM's perform. I will let you know how it goes.
@scottyuk et al - we are just proof testing a new set of coils, we normally test for interturn faults bt applying 220V 400Hz...
Thanks guys
All useful info. We will do them away from the rotor, so that sounds like it could work.
I share your nervousness electricpete but am also keen to experiment! So, we will take it slowly. Luckily it's bare copper so we can put a scope on pretty easily.
With regards brush seating grit, we have always been told to use 100 grit if the surface is highly polished. A wise old engineer once told me that too highly polished surface causes problems building a skin on the surface which can lead to high brush wear. We work to an ideal surface finish is...
Hi
We have been asked to perform a surge test on some salient pole field coils at 1500V. I am familiar with voltage drops using an AC supply at 50/60hz. Also aware of tests at higher frequencies (400Hz). But should I be concerned that user a standard surge tester (Baker type) we will overstress...
Hi
jog reverse means rotating in small increments in the revers direction ie iF you had a crane motor jog reverse would be used to move the crane in small steps (jog) when close to the object.
I am afraid this doesn't tell us what the direction of rotation is unfortunately.
How old is the machine? You may find a modern insulation system allows more copper to be used and this would be more beneficial than the mag wedges. Its difficult to quantify without knowing generator details. Why the need for a rewind? IS the core ok?
Hi Pete
I have been involved a few times (as a vendor). If its VPI and has been well impregnated it should be ok. Main problem area was the cable exits from the coil ends water seeps in the joints and fizzzzzzz.
The otehr problem we had (a long time ago) was rust at back of core - make sure...
jlamann
Firstly, the harmoncs are internal, they will not be seen outside the motor and you will not need any filters - apolgies if I have mislead you.
The effect will be second order in terms of temperature
rise and motor efficiency, the motor designer will incorporate this into the design...
I think the motor vendors would prefer three wire star connected. When connected in delta there will be third harmonic currents circulating which need to be considered in the design. If star connected, these currents cancel out and can be ignored. These affects are negligible on smaller motors...
