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GENERAL
On receipt the unit should be carefully unpacked and inspected
to ensure that no transit damage has occurred. Provided that this
inspection is satisfactory and reveals no evidence of damage then
installation can proceed.
If an electrical test is to be carried out prior to fitting the
power supply, it is essential that the person undertaking this work
be a qualified electronics technician who is fully aware of the
particular dangers associated with high voltage switch mode power
supplies. Metallic or conductive tools should not be used to adjust
any of the potentiometers. The unit has no user serviceable parts
and should not be dismantled.
DO NOT HANDLE OR TOUCH THESE UNITS WHEN THE SUPPLY IS CONNECTED.
AFTER DISCONNECTION FROM THE SUPPLY, ALLOW 30 SECONDS BEFORE HANDLING
SO THAT ALL THE CAPACITORS CAN DISCHARGE. To ensure that the output
is fully discharged short to ground before touching any high voltage
circuit.
Care should be taken not to operate the unit outside the specified
limits given above, failure to do so may damage the unit.
COMPLIANCE WITH SAFETY STANDARDS
The unit is designed to meet Normalised European Safety Standards
and hence installation of the power supply unit into the equipment
should comply with the following requirements.
a. A PROTECTIVE EARTH must be provided for safety in accordance
with EN61010 Part 1 : 1993 : Clause 6.5.1. The case of the units
should be bonded to this protective earth.
b. The output is classed as hazardous and must therefore not be
accessible to operators. The output must be isolated from accessible
circuits by Double Insulation or a protective screen as defined
in EN61010-1.
c. It is intended to be installed in an electrical enclosure and
the unit and its input connector should not be accessible to the
operator. Access should be restricted to authorised service personnel
only, with use of a tool. Care should be taken to prevent access
to the interior of the unit and protect against items (e.g. tools
or wires) inadvertently entering the interior of the unit.
d. The unit is not fitted with a fuse and so should be operated
from a limited supply of <8 amp.
INSTALLATION
The outputs of these units are considered hazardous and should
be installed such that they cannot become accessible. The output
should be connected such that the shortest creepage and clearance
path is to a protective earth connection. ENSURE that a LOW IMPEDANCE
connection is made to the unit chassis from the system PROTECTIVE
EARTH. The safety earth conductor must not contain any switches
or fuses.
Under worst case conditions the unit draws a current of 6A and
any input supply cable must be of a suitable type and rating. The
unit is not fitted with a fuse and so should be operated from a
limited supply. Fuses may be fitted externally to the unit to protect
unit and interconnecting wiring etc. but these should be rated to
prevent nuisance failures. Care should be taken in the design of
the interconnecting wiring within the system to ensure that connectors
with hazardous voltages cannot be connected to accessible circuits.
Ensure that the output is connected to the load prior to operation
of the unit and that a good low impedance high voltage joint is
made. Sharp points on either the high voltage or return joint should
be avoided as this will cause corona which will make the output
appear noisy. In general a tracking distance (creepage distance)
of 25mm (1 inch), per 10kV to earth is advised as a minimum to ensure
no breakdown or corona occurs, a much greater distance will be required
under adverse conditions. Care must be taken not to damage the cable
inner when forming the connections.
During arcing currents exceeding 1000 Amps will flow. It is important
that these currents return to the high voltage power supply by the
shortest possible route using the screen (shield) of the output
cable. Failure to observe this will result in the control terminals
of the unit seeing large voltage spikes during arcing and radiation
of electromagnetic interference.
Adequate ventilation should be provided to keep the unit cool
and the ventilation inlets should not be covered in any way. The
ambient air temperature around the inlet must not exceed 45 °C.
The unit is fitted with a thermal cut-out to protect itself should
the ambient temperature exceed this level. To restart the unit it
must be allowed to cool. De-asserting the INH input will then clear
the trip. The unit will operate in any orientation, however it is
not recommended to operate with the silk-screened face as the lowest
face.
OPERATING NOTES
1/ HIGH VOLTAGES ARE DANGEROUS. ENSURE THE OUTPUT IS FULLY DISCHARGED
BY SHORTING TO GROUND BEFORE TOUCHING ANY HIGH VOLTAGE CIRCUIT.
2/ The unit is short circuit proof but care should be taken that
the high voltage cannot be shorted into one of the control pin connections.
3/ TO ENABLE THE UNIT PIN 8 MUST BE TAKEN TO LESS THAN 1.5V WITH
RESPECT TO PIN 9.
There are three trips, over-temperature, over-current, and arc.
These are latching trips except for the arc trip, and are cleared
by cycling pin 8 or removing Power from the unit.
4/ POWER SUPPLIES ARE DISPATCHED WITH INTERNAL POTENTIOMETER SET
TO MAXIMUM. TURN DOWN TO ZERO BEFORE CONNECTING TO 24 VOLT SUPPLY.
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