Hi 7anoter4 (Electrical,
Thank you for your explanation.
" Isc=417/.05= 8340 A
For 1 sec Imax=sqrt (Isc^2*2sec) =sqrt (8.34^2*2) =11.7 kA .So 1.11KA for this xfrm is far from maximum permissible".
Yes the starting current is far from maximum permissible.
But i wonder the starting time is...
Hi 7anoter4 (Electrical),
COuld you please explain me how did you obtain the starting voltage drop of 373V=90%?
What is the cable impedance you consider? and what is the impedance of motor (at the time of starting) you considered?.
I would appreciate your explanation.
Thanks
Hi Skogsgurra, I would not worry if the control supply for existing motors taken from a secured source (UPS) but it is taken from its own bus hence there is a chance of dropping of other running motor contactors during starting of this 75kw motor.
Next one, the total starting load is not 150%...
Dear Folks,
I am working on a modification project (brown field, where new loads are going to be added in the existing power system.
Existing system:
Existing Transformer capacity is 300KVA, 11KV/415V, 417A, z= 5%,
Existing LV switchgear is 630A (Both breaker & bus bars).
Existing base load...
Hi Guys,
Thanks for your replies, i am sorry that i was out of office for last few days.
After this cable problem, I had checked all our 11kv cables / terminations and found similiar punctures and precipatations in 5 more cables.
These are occuring just 8 to 15 centimeters from the crunches...
Dear Gentlemen,
In our organisation, we have 20MG water tanks with CP and 8 test blocks are provided around each tank. Each test block consists of 3-terminals (structure, test coupon and reference cell). But these test coupons are not bonded with the structure. Is it require to bond the test...
Dear Gentlemen,
We have noticed a small puncture (approx 0.5 sq.mm )on R-core (near termination, both R-core and Y-core are touching each other)of XLPE 11kV cable at feeder end. And also noticed white precipitation around the puncture. But puncture is not upto the conductor level, perhaps pin...
Hi,
The first coil/core (0.5 class) of your PT is for metering pupose, and the second one, 6p, is for protection (residual voltage /open delta) purpose.
The standard accuracy classes for protective voltage transformers are 3p and 6p.
First letter indicates %voltage (ratio) error and phase...
Hi JFCWTR,
I agree with Mr dpc & Mr unclebob. Here is some more info.. Synchronous generators are standard in electrical power generation and are used in most power plants. Both Synchronous & Asynchronous(induction) generators are available in three-phase or single-phase systems. System...
Hi Gaggsy,
You shouldn't add all three currents for total current as these currents are individual pahses.
we can give only total power pulled by DB by adding individual powers.
if at all, you want to give total current of DB, you may take the max current i.e.7.2A in your case.
If supply voltage is balanced in all 3 phases, probably stator/rotor winding that could create unbalance.
Since DC resistance maynot reveal really unbalances, check for reactances (Z and phi/Z).
Motor tester (ALL Test) can help in finding the unbalances (in stator winding or rotor bars).
Varri
More vibration and sound is coming from the particular transformer but not other similar type transformers. Core bolts are tights and bed bolts are fixed with rubber pads. It is a stand-by transformer and usally operating without load.
Dear Gentlemen,
What are the reasons for vibration of dry type transformer enclosure? How can we find the cause?
Specs.:
Rating: 2000kVA, 11/0.414kV,50Hz dry type transformer
Your answer will be highly appreciated
