The distant position indication is a frequent need, in practice. This leaflet is adressed to power transformer engineers, specially when OLTC's are concerned. The contents, however, would be usefull in all areas where position indication is important (elevators, floodgates, etc.).
Electrical power transformers and regulators equipped with on load tap changers need local and/or distant indication of the operating position given by the OLTC.
LOEFER's digital position indicators provide local and/or distant identification of such positions, comprising not only straight numerical ranges such as 01......99 or double sided numerical ranges such as
-NN....-01, 00, +01....+NN, but also (when needed) letters added to the central positions such as 01, 02...09A, 09b, 09C...16, 17, for instance, meaning alpha-numeric ranges.
The indication occurs in a bright red 13mm led display located in the front of the apparatus.
2) AVAIABLE VERSIONS
Due to extreme operating and design differences, this leaflet will not describe digital position indicators fed by diode matrix. Please refer to our Diode Matrix. The three above mentioned types are avaiable in two basic alternatives:
2.1) Resistance Input.
2.1.1)WITHOUT EXTRA CURRENT OUTPUT. Terminals 4, 5 and 6 (figure-1) are directly connected to OLTC's resistive divider, where ohmic changes caused by tap changing are adequately transferred as a signal for the correct display indication. This alternative should be specified when single local or distant indication is required.
2.1.2)WITH EXTRA CURRENT OUTPUT. Two new terminals (7 and 8) are added, see fig-2, which provide the mentioned current output, and also shows that the way of connecting this position indicator to the resistive divider is different from the one seen in figure-1
Indicators with extra current output are subjected to serious damages in case operation occurs with broken or disconnected wiring on terminals 4, 5 and 6.
This situation is equivalent to a very large increase in the divider's ohmic value. The following consequences are expected:
- Output current rises to values far beyond the usual operating maximum. The display and devices connected to terminals 7-8 will probably be damaged.
-Internal overvoltages will mean damage risk for many components.
Under request, these indicators may be supplied in the "DB" version (Down-Scale Burnout) as described in our TDPdb Series Transducers
This kind of indicator should be specified when local indication is needed and and there is not enough place for a position resistance transmitter. The current signal, however is essential for a distant indicator and/or other indication or control devices.
2.2)CURRENT INPUT: Terminal 4 looses its electrical function and terminals 5 and 6 are fed by a resistance transmitter delivering a DC current signal which is proportional to the ohmic changes in the divider.
This current signal is the information needed for a correct display indication (see Fig-3)
This version should be specified when:
-Current signal has to be externally avaiable for other control or signal devices.
-Both local and distant indication are needed (see fig. 4)
3)POWER SUPPLY.
(All versions include galvanic insulation from feeding source)
4)MECHANICAL FEATURES.
The equipment is avaiable either:
4.1)In a 90x90x185 mm steel case protected by
an electrostatic dark-grey painting. For overall dimensions and
suggested panel cutout, refer to fig. 5.
The front panel is a 3 mm anodized aluminium plate containing
a 70x30 mm red acrilic window. Mounting occurs through two threaded
rods pressing the device against the customers panel.
4.2)Or in a 90x90x137 mm black ABS plastic casing, as seen
in fig. 6. The front panel is an all acrilic red plate. Mounting
occurs through side-mounted plastic clamps, as shown.
5)INDICATION POSSIBILITIES
6)THE EXTRA CURRENT SIGNAL OUTPUT
7)REQUIREMENTS FOR INPUT SIGNAL
7.1)RESISTANCE INPUT
7.2)CURRENT INPUT
Note: In connection with the current input, the input
impedance of the equipment must be taken into account, in order
to avoid exceeding load on the resistance transmitter.
8)ORDERING EXAMPLES
8.1 )Alpha numeric position indicator type IAP-3D/33/17ABC,
power supply 220 VAC 6O Hz, input 34x5 ohms, indicating range 01...17A,17B,17C...33.
8.2 ) Alpha numeric position indicator type IAP-3D/21/11ABC,
power supply 125 VDC, Input 0-5 mA, Zi = 200 ohms, indicating
range 01...11A,11b,11C...21.
8.3 ) Digital position indicator type IDP-2D/17, power
supply 200 VAC, 50 Hz, input 16x10 ohms, indicating range 01..........17.
8.4 ) Digital position indicator typeIDP-2D/08, power supply
127 VAC, 60 Hz, input 16x5, indicating range -08....-01, 00, +01....+08,
8.5 ) Digital position indicator with extra current output
typeIDPSC-2D/08, power supply 127 VAC, 60 Hz, input 16x5, indicating
range
- 08....-01, 00, +01....+08, current output 0-10mA, external
max. load 150 ohms
9)NOTES
9.1 ) For the applicable items, this equipment complies
with
9.2 )The text on the equipment, the technical pamphlets
and the routine test reports may be delivered either in portuguese,
spanish or english.
9.3 ) The contents of this leaflet are subjected to
changes without previous notice.
BACK
FIGURA 5
The IDP-2D and the IAP-3D digital
indicators and their corresponding IDPSC-2D and IAPSC-3D types
will accept any usual OLTC resistive divider, as long as the individual
resistors range from 5 to 20 ohms. Other individual ohmic values
may be considered under request.
Preferred input current ranges: 0-1
mA; 05 mA; 0-10 mA and 4-20 mA (DC). Other current
ranges may be considered under request.