Bypass Option; Surge Arrester; Maintenance - Sollatek AVR 3X20 Mode D'emploi

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The parameters monitored by the Three Phase AVS are:
a) Value of the Mains Voltage
The normal condition is when the values of the mains voltage of all the phases are within certain preset limits
referred to as the "window". The AVS detects when the voltage of any one or more phases goes outside the
window, either over- or undervoltage.
b) Phase Relationship (timing)
The AVS monitors the phase relationship between the three phases of the supply. The normal condition is when
the phase difference between the three phases is 120 degrees, corresponding to T/3 where T is the period of one
cycle.
c) Phase Rotation [optional]
The AVS can detect a phase rotation error of the three phase mains supply. Detection of parameters c) and d)
above is not standard, but are obtained by an optional plug-in board. On this board, it is possible to select by a
d.i.l. switch whether abnormality is indicated only, or it causes disconnection also.
4.3.2 Principle of Operation
The frequency and phase rotation detection circuits are explained in a separate section. The detailed operation
of the AVS in detecting the other parameters is given under CIRCUIT DESCRIPTION below. Basically, however,
the AVS compares the peak of the mains AC sinusoid of each phase with two references, one corresponding to
the lower or undervoltage limit of the window, and the other to the upper or over-voltage limit. If the mains is
normal, so that the peaks lie between the two limits and also within a time not exceeding T/3 (T is the period of
one cycle), a monostable is triggered which, after the wait time, switches the power to the equipment. If any one
or more of the peaks are below the lower limit, above the upper limit or the separation between two consecutive
peaks exceeds T/3, the AVS is reset to disconnect the equipment.
4.3.3 Checks and adjustments
a) Window Limits
P1 and P2 are adjusted to equalise the three phases, so that P1 adjusts the peak at the junction of P1 and R12, and
P2 at the junction of P2 and R20 to make them equal to the peak at the junction of R2 and R3. For measurement,
an ordinary multi-meter or digital multi-meter may be used on the AC range, since these give readings
proportional to peak.
P3 and P4 adjust the limits of the window. Start with these around the centre of their travel. Connect the normal
three phase supply to the AVS with one phase via a Variac and monitor voltage with voltmeter. Adjust Variac to
the under-voltage limit. Adjust P4 so that indication goes from Red to Amber. Adjust Variac to over-voltage limit.
Adjust P3 so that indication fluctuates between Amber and Red.
If the Variac is set so that the voltage is within the window, with Amber indicating, after the wait time (nominal 1
minute) Green will indicate and the contactor is energised.
For a complete check, three Variacs should be used, one on each phase, and the various combinations of under-
and over-voltage on each phase with the others tested.
b) Wait Time
The wait time is given by 0.7xR37xC6. With R37 = 820K and C6 = 100uF, the wait time is around 60 sec. to
within the tolerance of the components.
4.4 -HA Option
This option is available on all ratings of the AVR (Automatic Voltage Regulator) three phase units larger than
21kVA.
The standard Three Phase AVR provides an output which is stable to within + 4% given an input voltage variation
of + 27% from a defined nominal. Although it is likely that voltage stability of + 4% will meet most customers'
THREE PHASE AUTOMATIC VOLTAGE REGULATOR Issue: Feb 2002 THREE PHASE AUTOMATIC VOLTAGE REGULATOR Issue: Feb 2002
requirements, higher accuracy can be provided by incorporating a further 'fine' resolution stage beyond the
standard AVR system.
The standard AVR incorporates a fully electronic (static) 7-tap changing system providing an output regulated
to + 4%. This is fed to the -HA option which utilises a further 7 taps, again fully electronic, to achieve an output
stability of + 2.0%.

4.5 Bypass Option

4.5.1 Manual Bypass - This is used to take the AVR out of circuit, bypassing the supply straight to the load. A
fully rated, in line, mechanical switch is used to achieve this, as opposed to a relay or electronically based system.
This ensures that the supply to the AVR cannot be re-connected unintentionally by component failure or supply
disruptions. This is particularly important if the bypass is used to enable maintenance to be carried out.
4.5.2 Automatic Bypass - This facility operates to bypass the supply directly to the load in the event of a problem
associated with the AVR. If the temperature sensors built into the transformers detect that overheating is taking
place due to overloading, poor ventilation or high ambient, the bypass operates. Similarly, if the microprocessor
detects that a problem has occurred within the AVR itself, the supply is bypassed to the load.

4.6 Surge Arrester

4.6.1 Function - The unit is designed to prevent high voltage spikes and surges from causing damage either to the
AVR or to equipment down the line from the AVR. These spikes are commonly caused by lightning, sub-station
load switching or heavy motor load switching.
4.6.2 Operation - The unit is connected in parallel with the supply incoming to the AVR, forming a spur. If built
in to the AVR it will be situated above the connection terminals at the rear. Two indicators per phase are provided
to give warning of reduced protection level, in order that the surge arrester may be replaced before protection is
lost. The unit incorporates multi-stage MOV protection circuits.

5 Maintenance

This is a fully solid state AVR with no moving parts and therefore requires only the minimum of maintenance.
You can expect many years of trouble-free service with the AVR completely unattended.
Isolate the incoming mains supply before carrying out any maintenance.
The only maintenance required is to clean any dust and dirt from the outside and inside of
the casework which could be restricting the free ventilation of the equipment. If there is a
build up of dust on the PCB then this should also be carefully removed with a soft brush.
It is also wise on any equipment periodically to check the security of the electrical
connections and the condition of the cabling. Again ensure the power is turned off before
starting work.
If the AVR is damaged for any reason, or you suspect a fault, contact your nearest Sollatek
agent or Sollatek (UK) Ltd Head office for advice.
Sollatek UK Limited
Unit 10 Poyle 14 Industrial Estate, Newlands Drive, Poyle,
Slough SL3 0DX,
United Kingdom
Tel + 44 1753 688300 Fax +44 1753 685306 Telex : 849057 SUKL G
E-MAIL: sales@sollatek.com
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