Answer / sriman

OLTC MEANS ON LOAD TAP CHANGER
THE FUNCTION OF OLTC IS TO CHANGE THE VOLTAGE LEVEL OF
SECONDARY SIDE OF TRANSFORMER ACCORDING TO CHANGE IN LOAD
TO MEET THE REQUIREMENT AND TO KEEP THE VOLTAGE CONSTANT
WITHIN THE LIMITS

Answer / sabale.dnyaneshwar@gmail.com

OLTC MEANS ON LOAD TAP CHANGER. THE LOCATION OF OLTC IN
TRANSFORMER IS IN HV WDG. THE TAPPING IS TAKEN FROM HV WDG
B COZ
1. IN HV WDG NO. OF TURNS ARE MORE. SO,VOLTAGE REGULATION
IS GOOD.
2. THE HV WDG IS NEARER TO THE CORE. SO, THE TAPPING IS
POSSIBLE.
3. IN HV WDG CURRENT CARRING CAPACITY IS LESS THAN LV WDG.

THE FUNCTION OF OLTC IS TO GIVE CONSTANNT VOLLTAGE TO
SECONDARY WDG.

PLEASE GIVE ANY ANSWER THEN WELCOME
ANY DOUBT E MAIL ME. ON SABALE.DNYANESHWAR@GMAIL.COM

Answer / sailaja.k

hi Sabale.dnyaneshwar

ur answer is partly correct.
always LV winding is close to the core so that less
insulation can be provided b/w core & winding,
and the tappings are always on H.V(outer side of the core)

Answer / jitendra pawar

Onload Tap Changer (OLTC) is used with higher capacity
transformers where HT side voltage variation is frequent
and a nearly constant LT is required. OLTC is fitted with
the transformer itself. Multiple tappings from HV windings
are brought to the OLTC chamber and conacted to fixed
contacts. Moving contacts rotates with the help of rotating
mechanism having a spindle. This spindle can be rotated
manually as well as electrically with a motor. Motor is
connected in such a way that it can rotate in both the
directions so as to rotate the OLTC contacts in clockwise
and anticlock-wise direction. Two push buttons are fitted
on the LCP (local control panel) to rotate the motor and
hence the OLTC contacts in clockwise and anti-clockwise
direction. This movement of contacts thus controls the
output LV voltage of the transformer. So rotating of OLTC
contacts with spindle or push buttons in this way is a
manuall process. In case this process of rotating the OLTC
contacts and hence controlling the LV side voltage is to be
done automatically then a RTCC (Remote Tap Changer
Controller) is installed with the transformer HT Panel. The
RTCC sends signals to LCP and LCP in turn rotates the motor
as per the signals received from the the RTCC

Answer / krishnasingh

OLTC MEANS ON LOAD TAP CHANGER
THE FUNCTION OF OLTC IS TO CHANGE THE VOLTAGE LEVEL OF THE
SECONDARY SIDE OF THE TRANSFORMER ACCORDING TO CHANGE IN
LOAD SIDE TO MAINTAIN THE CONSTANT VOLTAGE WITHIN THE LIMITS
AND ALSO ITS A SAFETY DEVICE.

Answer / varun rekhi

Onload Tap Changer (OLTC) is used with higher capacity
transformers where HT side voltage variation is frequent
and a nearly constant LT is required. OLTC is fitted with
the transformer itself. Multiple tappings from HV windings
are brought to the OLTC chamber and conacted to fixed
contacts. Moving contacts rotates with the help of rotating
mechanism having a spindle. This spindle can be rotated
manually as well as electrically with a motor. Motor is
connected in such a way that it can rotate in both the
directions so as to rotate the OLTC contacts in clockwise
and anticlock-wise direction. Two push buttons are fitted
on the LCP (local control panel) to rotate the motor and
hence the OLTC contacts in clockwise and anti-clockwise
direction. This movement of contacts thus controls the
output LV voltage of the transformer. So rotating of OLTC
contacts with spindle or push buttons in this way is a
manuall process. In case this process of rotating the OLTC
contacts and hence controlling the LV side voltage is to be
done automatically then a RTCC (Remote Tap Changer
Controller) is installed with the transformer HT Panel. The
RTCC sends signals to LCP and LCP in turn rotates the motor
as per the signals received from the the RTCC


OLTC(on load tap changer)is a mechanism used in transformer
for changing the tapping position on primary side(HV)of
transformer.For any installation mostly in industrial areas
and rural areas the voltage on HV of the transformer will
not be 11kv(taking an example of 11kv System)and
correspondingly the output will not be 433v.To maintain a
constant 11kv/433v the tap changer on the Primary/HV side
of the transformer is either raised or lowered to maintain
constant 11kv input to transformer.Normally it is raised or
lowered in steps of 2.5% of normal KV value.

Answer / tse-wang

All answers are correct and more closely the answer No.3.
However, i am not comfortable with the fuction of the OLTC
described here in the forum:

The function of the OLTC (On-load-tap-changer) is to
maintain/regulate the output voltage of the transformer.
(This is general answer).

Technically, we are trying to change the winding turns
ratio (N2/N1) to change the mutual induction between the
two (or may be 3) windings.

Answer / mohd. karim

Sabale dnyaneshwar's Answer-3 is absolutly Right
100%

Answer / bhagya

A transformer tap is a connection point along a transformer
winding that allows a certain number of turns to be
selected. By this means, a transformer with a variable
turns ratio is produced, enabling voltage regulation of the
output. The tap selection is made via a tap changer
mechanism

Answer / borhan

In fact OLTC could be on/off load tap changer depended in
application.in distribution transformers it is off load tap
changer and in transmission field it is on load tap
changer.this is used to change the turning ratio of
transformer to have a constant measure for voltage when the
load is variable.

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