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This 'open-site' testing service was launched by Cranage in 2001 for large equipment which could not be accommodated in a calibrated test facility but which could be configured and operated on the factory floor under installed conditions. In-situ EMC tests and measurements are usually undertaken in support of a technical construction file (TCF) for the equipment under test (EUT). Although it would not be feasible to perform tests in full accordance with the relevant technical standards the testing methodology and procedures developed by Cranage EMC Testing Limited for in-situ testing have been assessed and approved for product certification by TUV International UK. Extent of Testing Compliance testing is performed to the philosophy of generic European Standards EN50081-1, EN50081-2, EN50082-1, EN61000-6-2, and the limits defined in the customers' Electromagnetic Compatibility Design Specification. EUT Configuration The equipment under test shall be set-up as per intended installation with normal earthing arrangements and should be positioned well away from any non-associated structure. Where possible, all input / output cables shall be connected, glanded and terminated in accordance with methods specified for the installation. For EUT's with continuous current rating up to 100A per phase, the incoming power line will be connected to the EUT via the Line Impedance Stabilisation Network (LISN). A single / three phase line filter is also used to attenuate electrical interference. An earth strap is bonded to the LISN and connected to the protective earth conductor of the incoming supply. The earth reference point of the LISN is also bonded to the safety earth of the EUT. Earth leakage current due to the LISN will exceed 80mA, therefore RCD protected supplies cannot be used - see note regarding personnel safety. For EUT's with continuous current rating greater than 100A per phase, the voltage probe method prescribed in CISPR16 shall be used. The incoming power line and protective earth conductors shall be connected to the EUT as per manufacturers installation instructions. This test can be performed on RCD protected supplies but may require measurements to be taken 'out-of-hours' if electrical interference on the incoming supply is significant. Connection details / requirements of the installation which cannot be fulfilled will be noted by the test engineer on EMC Test Worksheets. Mode of Operation Testing will be performed to simulate actual operating conditions. It may be necessary to assess more than one mode of operation to maximise emissions or determine worst case susceptibility. Monitoring during Testing Testing for susceptibility to electromagnetic disturbances will require the EUT to be monitored for maloperation. This may require external devices to be connected such as digital multimeters or audible transducers. Deviations on metering devices or control operations which exceed manufacturers specifications shall also be noted during testing and assessed with respect to the relevant performance criterion. A visual check of functionality, i.e. indicators and controls, will be made before and after testing. Preliminary Evaluation Prior to formal radiated emissions testing a preliminary evaluation is performed to establish if there are any potential areas of non-conformity. Cranage test engineers are trained to investigate problems and assist with corrective action. The modification state of the EUT is recorded by the test engineer on the EMC Test Worksheet. Test Schedule Conducted emissions testing precedes the test for radiated emissions. Tests for susceptibility which could have a damaging effect on the EUT will be performed towards the end of the scheduled test period. Transient burst and electrostatic discharge have been identified as being potentially destructive. Immunity tests for continuous conducted interference are extended from 80MHz up to 400MHz to assess the unaddressed frequencies in the lower part of the spectrum normally performed in a shielded test environment in the frequency range 80MHz to 1000MHz. Higher frequency immunity tests are performed on a spot frequency basis in cooperation with the Radio Communications Agency. Temperature and humidity are recorded on
a continuous basis throughout the tests. Humidity is particularly relevant
when evaluating susceptibility to electrostatic discharge. Deviations
outside 15 to 35 deg C and 30 to 60% are noted by the test engineer
on EMC Test Worksheets. 1) Conducted Emissions on Power Lines (terminal voltage disturbances) Frequency range: 150kHz
to 30MHz 2) Radiated Electric Field Emissions on EUT Boundary Frequency range: 30MHz
to 1000MHz 3) Conducted Susceptibility on Power Lines, Control, Signal and Earth Cables Frequency range: 150kHz
to 400MHz 4) Immunity to Electrical Fast Transient Bursts on Power Lines, Control, Signal and Earth Cables Burst frequency: 5kHz 5) Immunity to Electrostatic Discharge Test level: ±8kV
air discharge on user accessible non-conductive areas
Frequency range: 26MHz
to 1000MHz (10 spot frequencies*) * Test & Development licence (No. C/351) issued by the Radio Communications Agency Test Results A detailed test report is issued within an agreed timescale on completion of all tests. A test certificate summarising all EMC tests performed along with test levels and pass criteria can also be issued within an agreed timescale on completion of all tests. Personnel Safety Potential hazards will be present during the test period. The Cranage test engineer will inform the customer and any contractors of the potential hazards caused by the test set-up. A visual inspection is carried out by the Cranage test engineer to verify that 'Safe Working Practices for Cranage Testing Procedures' are being observed. Customer Agreement It is standard practice to seek the approval of a test plan prior to initiating test action. Test deviations from the plan are also noted in the test report. Cranage EMC Testing Limited has experience of preparing a test plan and would be pleased to assist in its formulation. |
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