Product Safety Standards for Audio Visual and Information Technology Equipment - Part 2, IEC62911

In Part 1 of this series, we looked at changed to the safety standards for Audio Visual and IT Equipment covered by IEC62368-1. As a follow up to that document we will now look at an accompanying standard IEC62911.

What is IEC62911?

The scope of this standard covers the routine electrical safety tests to be performed after manufacturing of complete equipment, sub-assemblies or components, which comply with IEC62368-1 (and additionally 60950-1 and 60065-1).

The aim of these electrical tests is to detect failures in the manufacturing process or unacceptable tolerances in the manufacturing or materials.

It allows for testing to be performed either on complete assemblies at the end of the production process or at a more optimal location as defined by the equipment manufacturer, providing that any further procedures could not adversely affect the safety of the equipment.

What tests should be performed as part of the routine test?

There are two main tests specified in IEC62911:2016, firstly the resistance of any protective bonding and secondly an electric strength test.

Resistance of Protective Bonding Test

This test, more commonly known as an Earth or Ground Bond Test should be performed on Class 1 products where a safety connection to ground is implemented. It is intended to prove that a sound connection exists between the mains earthing terminal and any exposed conductive points that are required to be protected. The test is not required on products where a functional earth is implemented.

This test is recommended to be performed as the first test, especially where the Protective Earth conductor may form part of the test circuit on subsequent tests.

Application of the Test

This test should be performed between the contact point on the mains plug of appliance inlet, or the protected earthing terminal of equipment designed to be permanently connected, and any accessible conductive parts that need to be connected to a protective earth.

For any device consisting of a socket outlet, provided to supply mains to other devices, the contact point of the socket must also be tested.

The test should apply a current, either a.c or d.c, of at least 150% of the rating of the overcurrent device but should not be less than 10A and not more than 25A.

The current source shall have a no-load voltage that does not exceed 12V.

The current shall be applied for aduration between 1 and 4 seconds, and the resistance measured.

What constitutes a good test?

The measured resistance on completion of the test shall not 0.1Ω. It is allowed that the power cord of the device is included in the resistance measurement.

If a power cord is included and the reading exceeds 0.1Ω, the resistance of the protective earth conductor of the power cord should be subtracted from the reading and the 0.1Ω limit applied.

Electric Strength Test

The electric strength test, commonly known as a Hipot test, is performed on all products, regardless of Class. The electric strength test is performed to ensure adequate insulation exists between mains connections and accessible conductive parts.

Application of the Test

The test should be performed between circuits connected to mains, and accessible conductive parts. For any accessible circuits not connected to the mains (i.e secondary circuits) where the insulation cannot be tested in the complete equipment, it is permitted for these to be tested separately.

In terms of connections the test voltage should be applied to the mains supply terminal (tied together) and accessible conductive parts or terminals regarded as accessible, that may become hazardous live in the event of an insulation fault as a result of incorrect assembly.

For any equipment powered by a.c, the test voltage should be either; 1) an a.c test voltage with a sine-wave having mains frequency, a d.c test voltage or a combination of both.

For equipment supplied by d.c mains, a d.c voltage should be applied.

For any equipment powered by either a.c or d.c mains the test can be either a.c or d.c provided the test voltage used is the equivalent of the highest of the two required test voltages.

The test voltage can be gradually raised from zero to the test voltage value, and should be held for 1 to 4 seconds.

All switches, including mains and functional switches conductively connected to mains shall be placed into the on position. It shall be ensured by suitable means that the test voltage is effectively connected to the equipment.

Test Voltages for equipment with a.c mains

The following test voltages should be applied to a product supplied with a.c mains.

Table 1: Test Voltages for Equipment powered from AC Source

Test Voltages for equipment with d.c mains.

For any equipment powered from a DC source, the following test voltages should be applied.

Table 2: Test Voltages for Equipment powered from DCSource

Actual Test voltage will depend upon the DC mains supply voltage, please refer to IEC62911:2016 for clarification.

What constitutes a Good Test?

There is no defined value (mA) for the limit of the test, no flashover or breakdown shall occur during the test.

The voltage source (test equipment) should have a current sensing device which will give a clear indication that the device has reached an unacceptable level of current (tripping current). Under load conditions (up to and including the overcurrent condition) the test equipment must be able to maintain the desired voltage.

The minimum tripping current can be set by the manufacturer. Consideration should be taken to ensure the set value is high enough to correctly detect breakdown, but also taking into account any potential safety issues for the test operators.

Activation of the current sensing device is defined as a flash over or breakdown and considered a fail.

Should I keep records of my production tests?

According to IEC62911:2016, the manufacturer of the equipment under test should keep records of the test results, the format of the result is not defined, and is left to the manufacturer.

The test data should be readily available and interpretable for all equipment leaving the production line.

The test records should contain the following information.

• Date the Test was Performed
• Model of the equipment tested
• Serial Number of the equipment (or another unique identifier)
• Location of the point tested
• Value of the Earth resistance and the corresponding current value
• Value of the test voltage used during the electric strength test
• A quick reference information to the success / failure of the test. i.e Pass / Fail

How can Seaward aid us in ensuring our production tests are compliant?

Our HAL range of test equipment is fully capable of ensuring your production testing requirements and comply with IEC62911.

With flexible and controllable earth bond testing capabilities of up to 40A and electric strength voltage output of up to 5kV a.c and 6kV d.c the test outputs are perfectly adequate for matching the test requirements no matter the device type to be tested.

In built flexible trip limits, combined with user programmable test sequences, ensures the product test is performed exactly and consistently every time.

The large inbuilt memory stores test records, and when combined with our Safety e-Base software, part numbers can be logged and used to determine the correct test parameters, results can even be directly transferred to a network location ensuring ultimate peace of mind for production line testing.

Along with our test equipment, we can offer bespoke in-site training for your team, ensuring the equipment is set up correctly and operators are able to test in a safe method with understanding of hazards that may arise during testing.

For more details, including video demonstrations, please visit the HAL Series webpage, or contact us if you have any questions.