One of the deadliest hazards to human life has a very simple name: “Leakage Current”. Leakage Current is the current that flows through a person when they touch an electrical product. The Leakage Current Test is a test that is performed on all cord connected products but a test that few people understand. Let’s review the elements of this test:

Purpose of the Test is to measure the amount of current that passes through a person when that person touches an electrical product. For example, when you touch a vending machine, electrical current is passing through your body from the vending machine.

1) A few related facts about the human body:

2) Electrical current follows the path of least resistance. And you know from above that the human body is represented by an R/C network (resistor/capacitor) = a resistance that is much greater than a grounding wire. As such, all leakage current will bypass the user and go to ground (earth) for a reliably grounded product.

Test Method involves fully energizing and operating the product being tested as it is intended.

Mains Test Power Configurations are a part of the leakage current test that most test personnel conduct without understanding or considering the reason.

Test Objectives: The objective of the Leakage Current test is to verify that the electrical insulation used to protect the user from a Risk of Shock is suitable for the application. Leakage Current testing is used to verify that the product does not leak excessive current when contacted by the user.

  1. Excessive leakage current can cause the heart to go into ventricular fibrillation resulting in cardiac arrest which can lead to death.
  2. Leakage current measurement levels depend on the amount of capacitance in the products’ solid insulating materials. Different types and number of layers of an electrical insulation results in varying amounts of inherent capacitance through the insulation. This capacitance causes low amounts of current to “leak” through the insulation.
  3. Leakage current levels can be significantly elevated in products that are subject to EMI requirements (FCC, CE-EMC). These products must incorporate EMI filters on their incoming mains power to provide clean power to sensitive electronics while also protecting from radiating emissions back onto the power line. These filters incorporate capacitors to ground, these capacitors can cause high leakage current when operating normally. If the product is for professional use only, the standard may permit high leakage current with warning markings for the user to insure the product is reliably grounded (so the user isn’t subjected to the high leakage current). Otherwise, an isolation transformer must be added to power the product thereby isolating the product from ground – which will almost eliminate leakage current to ground.

As you can see, we don’t simply perform the tests because they are in the standard. Each test in the standard has a set of objectives that relate to the 6 Hazards of Product Safety. The Leakage Current Test is performed as part of the Risk of Shock compliance review. High leakage currents cause cardiac arrest leading to death. It is therefore a very important test – another test that directly saves lives.

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