Safety Certification General Testing Category
Generally speaking,safety regulations referred to varies in accordance with the evaluated product. Testing categories increases and decreases, there are also deviations in testing conditions. Below are the general product safety testcategories :
Hazard Energy Test
Hazard Energy test:
Testing Purpose:
User may contact areas, such as the power supply output terminals. Therefore, test fingers are used to test ifhazardous energy terminals can are touchable risk.
Test Method:
1.Connect all output load to an electronic load.
2.If input power of EUT is AC power, connect AC power supply to EUT and adjust test voltage 1.1 times the labeled voltage during the test. Adjust the impedance of the electronic load slowly in order to measuremaximum output voltage (no-loadvoltage), maximum current (Collapse current, current should continue for one minute) &maximum power (corresponding current multiplied by voltage).
3.If input power of EUT is DC power, connect DC power supply to EUT and adjust test voltage 1.2 times the labeled voltage during the test. Repeat step 2 to measure maximum output voltage (no-load voltage), maximum current (Collapse current, current should continue for one minute) & maximum power (corresponding current multiplied by voltage)
4.EUT: U=1.06 or 1.1Un, F=Fn
5.Output between any two points are connected to a variable resistance load, the load is adjusted to get max. output power. The measurement can be done between output of the terminals and earth.
6.Output voltage and current that generate the max. power shall be recorded.
7.Max. voltage and capacitance between the above two points shall be recorded.
8.Test finger in straight position is applied without appreciable force between two points
Determine methods:
This measurement provides as a reference for in charge of safety only. Maximum power should not exceed 240VA. Ifresult exceeds 240V indicates that there is risk of energy, please contact the project engineer immediately.
Note:
1.When the load increases while the voltage drops below 2V, that the energy security, select the maximum power (to adhere to one minute) before the voltage falls below 2V.
2.When voltages drops to 2V, add load until maximum current is measured (short-circuit current)
Discharge of X-Capacitors
Discharge test:
Testing purpose:
When the AC power plug is pulled out, the electricity stored in the primary X-capacitor which is connected to the primary circuit should be designed no risk of electric shock.
Test Method:
1.All output load of the EUT should not be connected to the load.
2.Connect the fixture output plug to the output terminal of the EUT. Connect the oscilloscope to the fixture terminal and connect the power to the fixture output socket. Adjust test voltage 1.1 times the labeled voltage during the test. Measurethe discharge time.
3.EUT: U=1.06Un or 1.1Un, F=Fn, with maximum X-capacitors, maximum bleeding resistors installed.
4.Load of the EUT is minimum load or no load.
5.Measurement of the voltage decayed, shall be achieved by storage oscilloscope having high input impedance (>10 MW).
6.The power switch of the EUT shall be either in ON or OFF position.
7.The voltage after disconnection power source for 1 s / 10 s is recorded.
8.Several times of trying may be needed to get a higher voltage of disconnection moment.
9.When the total capacitance of the X-capacitor is not more than 0.1 uF, no test is required.
10.When testing the discharge voltage by oscilloscope, dc coupling shall be used.
11.When connecting the probe of oscilloscope, the Reference of the probe shall be connected to the Neutral of mains. If both poles are live, the earth of the oscilloscope shall be floating.
Determine methods:
Discharge test time is the key to the judgment, if the highest voltage value stored in the X-capacitor begins to discharge, and must discharge to the voltage value of 37% about one second, otherwise please notify cases of the engineers to do the processing.
Limited Power Source Test
Limited Power Source Test
Testing purpose:
Determineif the output energy from the output terminal of the product is a limited power source. If it isa limited power source, its power supply is allowed to use HB grade material. Afire enclosure is not necessary.
Test Method:
1.Load all output load of the EUT.
2.If input power of EUT is DC power, connect DC power supply to EUTand adjust test voltage 1.06 times the labeled voltage during the test before adjusting the electronic load. Set a load step and adjust the load step everyminute until EUT crashes. Record maximum voltage, crash current, maximum power. Perform normal and abnormal test. Short-circuit opto-coupler or current limiting resistor are referred to as abnormal test.
3.If EUT output is DC power, change it to DC and repeat step 2.
4.EUT: U=Un, F=Fn, output terminals of limited power source circuit are connected to a variable resistor to measure maximum output current.
5.Volt meter and current are connected to measure the voltage and current.
6.Uoc: is output voltage measured with EUT, U=1.06 or 1.1 Un, with output load disconnected.
7.Isc: is maximum output current after 5s of operation with any load, including short.
8.VA: is maximum output VA with any load, initial transients £ 100 ms are ignored.
9.If a regulating network is used to limit the output, both normal and single fault condition in the regulating network circuit (open or short-circuit) shall be tested.
10.Limits shall refer to table 2B and 2C as applicable.
Determine methods:
1.If EUT relies on the inherent circuit protection, please refer to Table 2B
2.If EUT relies on external components for protection, refer to Table 2C
Grounding Impedance Test Introduction
Grounding Impedance Test
Testing purpose:
Test grounding function of EUT’s metal casing or grounding parts.Are in good grounding function.Todetermine if it could act as a re-grounding protection function.
Measurement Equipment:
1.Grounding Tester. The calibration validity for each equipment shall be checked.
2.Before measurement, the tester shall be checked with the testing current and limit value of the resistance. The tester is then checked by connecting the probes together for low resistance and zero adjustment. And, open the testing circuit for the high resistance checking.
Method:
If the current of the circuit is 16A or less:
1.The test current is 1.5 times current rating of the circuit (For UL and CSA 60950, the test current shall be 2 times)
2.The test voltage does not exceed 12 V; and test duration is 60 sec. (For UL and CSA 60950, the duration is 120 sec.)
3.The resistance of the connection between the protective grounding terminal or grounding contact and parts required to be earthed shall not exceed 0.1W.
4.If the current of the circuit is exceed 16A:
5.The test current is 2 times current rating of the circuit (For UL and CSA 60950, 2 times)
6.The test voltage does not exceed 12 V; and test duration is 120 sec. (For UL and CSA 60950, the test duration shall follow the table in the standard)
7.The voltage drop across the bonding conductor shall not exceed 2.5V
8.The resistance of the protective grounding conductor of the power supply cord is not included in the resistance measurement.
Determine methods:
The impedance should not exceed 0.1Ω or the drop voltage is no more than 2.5V
Humidity Condition Test
Humidity Condition Test Introduction
Testing purpose:
To ensure that analog products could work inbad environment for long hours withoutcausing insulation breakdown and risk of electrical shock.
Test Method:
1.EUT is not energized, any removable parts are removed, doors are left opened.
2.Place the EUT in the testing area for 24 h and measure the ambient temperature ta°C.
3.Setting cabinet for 93% RH, ta-2°C (but must between 20-30°C, maintained within 1°C). EUT is placed in that cabinet for 48 h. Care is taken that when putting the EUT into the cabinet, condensation does not occur. Setting the timer as 48 h count down.
4.After 48h, remove the EUT from cabinet to testing area.
5.The insulation is then subjected to electric strength test.
Determine methods:
After test is completed, no insulation breakdown should occur after pressure test.
Mechanical Tests (impact test, drop test, push and pull test...)
ImpactTest
Testing purpose:
Housing should have sufficient mechanical strength. Its structure should be able to withstand a variety of situations may be encountered in use.
Test Method:
1.External enclosures which would give access to hazardous parts shall be tested.
2.EUT consisting of complete enclosure shall be tested.
3.Each enclosure material shall be tested.
4.EUT is supported in its normal position on a hard surface.
5.A steel ball, 50mm in diameter, 500g is dropped freely from 1.3 M high onto the EUT enclosure.
6.Only top and side of the enclosure planes are tested.
7.Vertical planes could be tested by turning the EUT.
8.Test is not applied to flat panel display or platen glass of the EUT (e.g. copying machine, scanner etc.)
Determine methods:
After test, there shall be no component exposed to the user and EUT should also to meet insulation requirements.
Normal Operation Temperature Test
Temperature Rise Test
Testing purpose:
EUT during normal use, the components’ material, enclosure, etc. shall not exceed defined security value to ensure EUT is not at high temperature risk.
Test Method:
1.EUT primary is U=Un, F=Fn, operated under normal max. load.
2.Primary voltage is then increased to its upper voltage tolerance (+6% or +10%) or lower (-10%) without change the load.
3.Temperatures of parts are measured by thermal couplers, windings are measured by resistance change method.
4.Measuring place shall be a point close to the heat source.
5.The test is continued until thermal stable.
6.Voltage is changed lower or higher tolerance without rest of time.
7.Afault conditions test shall be continued after the heating test if there are openings for ventilation purpose with the openings blocked. U=Un.
Determine methods:
The measured temperature should not exceed the temperature limit.
Plastic Material Test (Ball pressure test, Resistance to heat / resistance to fire test...)
Ball Pressure Test
Testing purpose:
To examine the heat-shrink resistible material will soften or deform at be change at high temperature.
Test Method:
1.Thermoplastic parts on which parts at hazardous voltage are directly mounted is tested.
2.Ball pressure test apparatus is weighing 20N, contact point is a 5 mm diameter steel ball.
3.Heating cabinet is 40K higher than max. temperature rise of that part test during heating test, but ³125°C.
4.After 1 h test, the sample is removed and cooled down to room temperature withing10s by immersion in cold water.
Determine Method:
The diameter of the depress part shall be no larger than 2mm.
Touch Current / Leakage Current Test
Touch Current Test
Testing Purpose:
To ensure parts at human reach such as enclosure, terminals, etc..has noelectric shock risk.
Testing Method:
1.EUT primary is U=1.06 or 1.1Un, F=Fn (upper), secondary circuits are disconnected from other equipment.
2.Earth conductor of the EUT disconnected. EUT is placed on an insulated table or stand.
3.Class II equipment or class II construction, the user accessible area is test by a metal foil 10cm X 20 cm.
4.If Y-capacitor is provided, the test shall be conducted under max capacitance of the Y-capacitor that the manufacturer wishes to use and shall be recorded.
5.Test is made with both Line and Neutral conductor. Power switch of the EUT, if any, shall be opened or closed in all possible position.
6.Figure D.1 or D.2 is used as appropriate.
Determine methods:
Please refer to Table 5A below
Fault Conditions Test (Abnormal operation, Components fault, Stalled fan...)
Fault Conditions Test
Testing purpose:
To ensure thatseven dangers (fire, electric shock, energy, explosion, chemical, mechanical, radiation and other safety hazards) doesn’t occur at abnormal working conditions.
Test Method:
1.EUT is operating under normal load, U=0.9, 1.06 or 1.1Un, F=Fn. A fault is then introduced. One fault only at a time.
2.Ventilation openings shall be blocked; Semiconductors shall be short-circuited or open-circuited one at a time; Transformer secondary windings are short-circuited one at a time (other windings are normal loaded); Transformer secondary windings are overloaded one at a time (other windings are normal loaded), Fan is locked; Operational insulation which clearances or creepage distances are less than requirement, is short-circuited; Motors are locked.
3.The input current, fuse rating current, test duration and observation shall be recorded.
4.The test is continued until a protection device opened the circuit (fuse) or steady state conditions.
5.Overload test and fault condition which the current is more than normal current, shall wait until thermal stable, coil temperature of transformer shall be recorded.
Determine methods:
No insulation breakdown should occur after test completed.
Electric Strength Test
Electric Strength Test
Testing purpose:
Consider whether the product has adequate electrical strength.
Testing Method:
1.The test is made while the EUT is still in well-heated condition (immediately after 4.5.1 heating test).
2.Make sure the power switch of the EUT is in ON position.
3.Thin material can be tested in room temperature.
4.The test voltage is a.c. of 50 or 60 Hz or d.c. voltage equal to peak voltage of the a.c. voltage.
5.Test voltage is applied gradually raised from zero to the specified voltage and held at that value for 60s.
6.Insulation breakdown is: Current flows through the insulation rapidly increases in an uncontrolled manner; that is the insulation does not restrict the flow of the current.
7.Corona discharge or a single momentary flashover is not regarded as insulation breakdown.
8.A test incorporating reinforced insulation and lower grades insulation (BI, SI), care is taken not to overstress BI or SI.
9.Where capacitors (X or Y capacitors) are across the insulation, d.c. voltage is recommended for the test.
10.Discharge resistors shall be disconnected before testing.
Determine methods:
No insulation crash should occur after test completed.
Stability Test
Stability Test
Test Objective:
In normal use, parts or products should not lose stability and endanger the safety of users and maintenance personnel.
Test Method:
1.When EUT is placed on the table or moved frequently at normal use, put EUT on a tilted plane of 10ºC. During the test, doors or drawers of EUT are placed at the most severe condition.
2.If the product is placed on the floor at normal use, and weighs more than 25kg, apply a force that is 20% the weight of the product(but should no greater than 250N)at the highest point( but no greater than 2M, and should not push up) of the EUT. During the test, all jacks that are used at normal use should be positioned. Additionally, all doors and drawers should be placed in most unfavorable position.
3.As for another test especially for EUT placed on the floor, all doors and drawers shall be opened. Impose a vertical downward 800N force on the EUT, put the EUT on a platform no lower than one meter or an obviousplane.
Determining methods:
The EUT shouldn't dump.
Power Cord Test (tensile testing, the thrust test, torque test...)
Power Cord Tensile Testing
Testing purpose:
To testif the tension a user-irremovable power cord can bear can meet the standard requirement.
Test Method:
1.Use hand to push back the power supply cord into the EUT.
2.Use hand to rotate the power supply cord.
3.Cord is subjected to 25 times of pull force in the most unfavorable direction, each time 1 s. Test force: M£1 kg (30N); 1<M£4 kg (60N); M>4 kg (100N).
4.The power cord shall not be displaced by more than 2 mm.
Determine methods:
Test the power cord should not be pulled out 2mm.
SELV Voltage Measurement Test
SELV Voltage Test
Testing purpose:
To make sure that both measured results in the case ofnormal or single fault is a SELV circuits.
Test Method:
1.EUT: U=1.06 / 1.1Un, F=Fn, under any load conditions which can generate maximum output voltage.
2.Each single SELV circuit or interconnected SELV circuits are measured.
3.A single failure of basic insulation or supplementary insulation or of a component failure is simulated one at a time.
4.Voltages at the SELV circuits are measured by storage oscilloscope. Measurement is at least 0.2s.
5.Components with double or reinforced insulation are not simulated.
Determine methods:
Oscilloscope measurements in normal and abnormal test should not exceed 71V (peak) or 120V (DC) voltage. After 0.2 seconds, resultshall not exceed 42.4 V(peek)or 60V (DC).
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