Hypertherm HyIntensity Fiber Laser Rev.3 - Manual (Page 24)

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PS-2 H ypertherm Fiber Laser Instruction Manual – 807090 Revision 3
protective earth connections, fuses, supply disconnecting
device, and type of supply circuit. Read these instructions
before installing the equipment. The first and most
important step is the safety assessment of the installation.
The safety assessment must be performed by an expert,
and determines what steps are necessary to create a safe
environment, and what precautions should be adopted
during the actual installation and operation.
Procedures for periodic inspection
and testing
Where required by local national regulations,
IEC 60974-4 specifies test procedures for periodic
inspection and after repair or maintenance, to ensure
electrical safety for plasma cutting power sources built
in conformity with IEC 60974-1. Hypertherm performs
the continuity of the protective circuit and insulation
resistance tests in the factory as non-operating tests.
The tests are performed with the power and ground
connections removed.
Hypertherm also removes some protective devices
that would cause false test results. Where required by
local national regulations, a label shall be attached to
the equipment to indicate that it has passed the tests
prescribed by IEC60974-4. The repair report shall
indicate the results of all tests unless an indication is
made that a particular test has not been performed.
Qualification of test personnel
Electrical safety tests for shape cutting equipment can
be hazardous and shall be carried out by an expert in the
field of electrical repair, preferably someone also familiar
with welding, cutting, and allied processes. The safety
risks to personnel and equipment, when unqualified
personnel are performing these tests, may be much
greater than the benefit of periodic inspection and testing.
Hypertherm recommends that only visual inspection
be performed unless the electrical safety tests are
specifically required by local national regulations in the
country where the equipment is installed.
Residual current devices (RCDs)
In Australia and some other countries, local codes may
require the use of a Residual Current Devices (RCD)
when portable electrical equipment is used in the
workplace or at construction sites to protect operators
from electrical faults in the equipment. RCDs are
designed to safely disconnect the mains electrical supply
when an imbalance is detected between the supply
and return current (there is a leakage current to earth).
RCDs are available with both fixed and adjustable trip
currents between 6 to 40 milliamperes and a range of trip
times up to 300 milliseconds selected for the equipment
installation, application and intended use. Where RCDs
are used, the trip current and trip time on RCDs should
be selected or adjusted high enough to avoid nuisance
tripping during normal operation of the plasma cutting
equipment and low enough in the extremely unlikely event
of an electrical fault in the equipment to disconnect the
supply before the leakage current under a fault condition
can pose a life threatening electrical hazard to operators.
To verify that the RCDs continue to function properly
over time, both the trip current and the trip time should
be tested periodically. Portable electrical equipment
and RCDs used in commercial and industrial areas in
Australia and New Zealand are tested to the Australian
standard AS/ NZS 3760. When you test the insulation
of plasma cutting equipment to AS/ NZS 3760, measure
the insulation resistance according to Appendix B of
the standard, at 250 VDC with the power switch in the
ON position to verify proper testing and to avoid the
false failure of the leakage current test. False failures
are possible because the metal oxide varistors (MOVs)
and electromagnetic compatibility (EMC) filters, used to
reduce emissions and protect the equipment from power
surges, may conduct up to 10 milliamperes leakage
current to earth under normal conditions.
If you have any questions regarding the application or
interpretation of any IEC standards described here, you
are required to consult with an appropriate legal or other
advisor familiar with the International Electrotechnical
standards, and shall not rely on Hypertherm in any
respect regarding the interpretation or application of such
standards.