Today we’ll be discussing the various “testing” cords must go through in order to be 100% ready to go and meet the requirements for the UL standards (or international safety agency approvals) of cord sets and power cord supplies.
UL generates standards and test procedures for products and equipment focusing on product safety. Power cords undergo some of the most common tests:
- A grounding test. The purpose of a grounding test is to protect the consumer from hazards that can be caused by a faulty ground connection. A ground bond test is a high current AC test that measures resistance of the ground path under high current conditions.
- The continuity test is carried out under high current, simulating a fault to earth. This test is performed by applying an AC or DC current between the conductive surface and protective earth.
- There is a hi-pot test. This is a stress test of the insulation of a device under test DUT (Device Under Test). This means the voltage used in a hi-pot test can either be AC or DC.
- An AC test must consider the effects of real and reactive current.
- When an AC voltage is applied, the current that flows is equal to the voltage divided by the impendence.
- A polarity test is usually performed as a part of a hi-pot test. It is a simple test that verifies that a product with a polarized cord (3-prong-plug or a 2-prong-plug) is properly connected.
- The insulation test determines how effective the insulation is in resisting the flow of electrical current.
- Lastly, we have the pull-test. A pull-test is where a wire is pulled upward (effectively pulling it away from the substrate) by a hook until there is either a bond failure or the wire breaks. The connection between the blade terminal and the conductor shouldn’t break under a weight pull force of 20-30 lbs. for one minute.
Additional tests power cords undergo are:
- Flame test
- Physical properties
- Heat shock
- Low temperature
- Blade security
- Strain relief
- Flexing test
Power cords meet the requirements under UL standards, once they pass all of these important tests.