Browse  |   Placement Papers  |   Company  |   Code Snippets  |   Certifications  |   Visa Questions Post Question  |   Post Answer  |   My Panel  |   Search  |   Articles  |   Topics  |   ERRORS new

 Categories >> Engineering >> Electrical Engineering

 Civil Engineering Interview Questions (3011) Mechanical Engineering Interview Questions (3270) Electrical Engineering Interview Questions (13222) Electronics Communications Interview Questions (2348) Chemical Engineering Interview Questions (407) Aeronautical Engineering Interview Questions (76) Bio Engineering Interview Questions (16) Metallurgy Interview Questions (79) Industrial Engineering Interview Questions (162) Instrumentation Interview Questions (2317) Automobile Engineering Interview Questions (104) Mechatronics Engineering Interview Questions (38) Marine Engineering Interview Questions (43) Power Plant Engineering Interview Questions (73) Engineering AllOther Interview Questions (1189)
Question
`what is  dyn 11`
Question Submitted By :: Saeed581
I also faced this Question!!     Rank Answer Posted By

Re: what is dyn 11
# 1
dyn11 is vector group of transformer
 Is This Answer Correct ? 2 Yes 1 No
Kaustubh

Re: what is dyn 11
# 2
dyn11 is vector group of transformer it it delta-star with
neutral with 30 degree phase shift it is used for
distribution transformer.

 Is This Answer Correct ? 6 Yes 0 No
Bharatelectrical
[Century Rayon]

Re: what is dyn 11
# 3
What do you mean by vector group of a transformer?
Ans:-
The vector group denotes the way in which the windings of a
transformer are connected and the phase position of their
respective voltage vectors.
The following examples are for two winding three phase
transformers:
So, what does Dd0, Dyn11, YNd5 etc. mean?
First symbol/symbols, capital letters: HV winding
connection.
Second symbol/symbols, small letters: LV winding
connection.
Third symbol, number: Phase displacement expressed as the
clock hour number.
The ANSI notations are not identical to the IEC marketplace
(See ANSI/IEEE Std C57.70). For the IEC marketplace the
winding connections are categorized as follows:
a) Delta (D,d)
b) Start (Y,y)
c) Interconnected Star (Z,z)
d) Open (III, iii)
Winding connection designations
High Voltage Always capital letters
Delta - D
Star - S
Interconnected star - Z
Neutral brought out - N
Low voltage Always small letters
Delta - d
Star - s
Interconnected star - z
Neutral brought out - n

Phase displacement
Phase rotation is always anti-clockwise. (international
Use the hour indicator as the indicating phase displacement
angle. Because there are 12 hours on a clock, and a circle
consists out of 360°, each hour represents 30°.
Thus 1 = 30°, 2 = 60°, 3 = 90°, 6 = 180° and 12 = 0° or
360°.
The minute hand is set on 12 o'clock and replaces the line
to neutral voltage (sometimes imaginary) of the HV winding.
This position is always the reference point.
Because rotation is anti-clockwise, 1 = 30° lagging (LV
lags HV with 30°)and 11 = 330° lagging or 30° leading (LV
leads HV with 30°)
Dd0
Delta connected HV winding, delta connected LV winding, no
phase shift between HV and LV.
Dyn11
Delta connected HV winding, star connected LV winding with
neutral brought out, LV is leading HV with 30°
YNd5
Star connected HV winding with neutral brought out, delta
connected LV winding, LV lags HV with 150°
The phase-bushings on a three phase transformer are marked
either ABC, UVW or 123 (HV-side capital, LV-side small
letters)
Two winding, three phase transformers can be devided into
four main categories (Clock hour number and phase
displacement of those most frequently encountered in
practice in brackets)
Group I - (0 o'clock, 0°) - delta/delta, star/star
Group II - (6 o'clock, 180°) - delta/delta, star/star
Group III - (1 o'clock, -30°) - star/delta, delta/star
Group IV - (11 o'clock, +30°) - star/delta, delta/star
(Minus indicates LV lagging HV, plus indicates LV leading
HV)
Group I
Example: Dd0 (no phase displacement between HV and LV)
The conventional method is to connect the red phase on A/a,
Yellow phase on B/b, and the Blue phase on C/c. Other phase
displacements are possible with unconventional connections
(for instance red on b, yellow on c and blue on a) By doing
some unconventional connections externally on one side of
the trsf, an internal connected Dd0 transformer can be
changed either to a Dd4(-120°) or Dd8(+120°) connection.
The same is true for internal connected Dd4 or Dd8
transformers.
Group II
Example: Dd6 (180° displacement between HV and LV)
By doing some unconventional connections externally on one
side of the trsf, an internal connected Dd6 transformer can
be changed either to a Dd2(-60°) or Dd10(+60°) connection.
Group III
Example: Dyn1 (-30° displacement between HV and LV)
By doing some unconventional connections externally on one
side of the trsf, an internal connected Dyn1 transformer
can be changed either to a Dyn5(-150°) or Dyn9(+90°)
connection.
Group IV
Example: Dyn11 (+30° displacement between HV and LV)
By doing some unconventional connections externally on one
side of the trsf, an internal connected Dyn11 transformer
can be changed either to a Dyn7(+150°) or Dyn3(-90°)
connection.
By doing some unconventional connections externally on both
sides of the trsf, an internal connected groupIII or
groupIV transformer can be changed to any of these two
groups. Thus, an internal connected Dyn1 transformer can be
changed to either a: Dyn3, Dyn5, Dyn7, Dyn9 or Dyn11
transformer, by doing external changes on both sides of the
trsf. This is just true for star/delta or delta/star
connections.
Changes for delta/delta or star/star transformers between
groupI and groupII can just be done internally.

 Is This Answer Correct ? 12 Yes 0 No
Dhiren

  Question Asked @ Answers Other Electrical Engineering Interview Questions why the stator is not laminated in DC machines? 4 why the generating voltage in India is 11kV or why is it be transmitted as multiples of 11 ACC 27 why capacitor is not discharged phase to body 1 1.where in India the maximum transmission voltage is operated? 2.what the methods are used to cool down the transformer?give the specific ratings of the transformer & specific cooling process. 3.how zero & negative sequence reactances are formed in a rotating machine when fault occur in the system? IES 2 what are the specifications for Dc cables of higher rating Reliance 1 What is a liquid resistance starter?where it is used?? Mecon 9 Hello friends., my question is related to testing of current transformer... A Ct having knee point voltage of 750 volts., and I have two step up transformer's of rating 230 v to 440 volts., can I obtain the value of 750 volts by using the two transformer's.... If yes then how could I connect the transformer's to obtain knee point voltage?? thank you in advance ABB 1 what is the ambient temperature of transformer oil & winding? Reddy-Labs 2 Which UPS (inverter) is better and why ? 12 V inverter and 24 V (two 12 V batteries in series) inverter which is better ......... which has the longer backup which has the greater charging time which has the greater discharging time thank you 1 What is the difference between MCCB and MCB ? Siemens 3 Cummins 750 KVA generator how much disel consumed per hour and how many units generated on 100% full load. 1 What happen when ct secondary are open circuited? why same thing is not happen in ordinary transformer? BARC 3 For more Electrical Engineering Interview Questions Click Here