Posted on 14 Jul, 2016 by Russell Poppe
Electrical safety testing is an essential step in the manufacturing process for any product that uses electricity.
According to Ellis Whittam, around 25 people die every year as a consequence of electrical accidents in the workplace - and 1,000 electrical accidents are reported annually to the Health and Safety Executive (HSE).
Therefore, it is imperative for original equipment manufacturers (OEMs) to do as much as they can to reduce the risk of electric shock from their products. Electric shocks not only cause injuries and deaths directly, but also indirectly – for example, construction workers may fall from ladders or scaffolding if they receive a shock while using faulty equipment.
OEMs that manufacture electrical equipment that is designed or adapted for use between 50 and 1,000 volts (in the case of alternating current) or 75 and 1,500 volts (in the case of direct current) must comply with the Electrical Equipment (Safety) Regulations 1994. You can read about the relevant requirements in detail here.
In this post, we will consider three different types of electrical safety testing that OEMs should be implementing as part of a robust electrical safety testing strategy.
Portable appliance testing
The simplest form of electrical safety testing is portable appliance testing (PAT). A portable appliance is generally defined as a product that can be easily moved from one place to another, encompassing kettles to printers; hairdryers to electric drills.
With this test method, a product is first visually inspected to check for any visible signs of damage - for instance, frayed cables or bent pins on plugs - before being connected to PAT equipment. This is a simple machine that checks whether the relevant electrical components are sufficiently insulated.
For higher voltage products, a flash test - also known as a hipot (high potential) test or dielectric withstanding voltage (DWV) test - should be implemented. This test method checks whether the electrical insulators in finished products – such as printed circuit boards (PCBs), cables and electromechanical assemblies - have enough dielectric strength for the working voltage, thereby safeguarding against electric shock.
Writing for Electronic Product Design & Test, Stewart Haile says: "The test is designed to detect that gaps or clearances between conductive parts and earth are sufficient and that damage in the form of pin holes/ cracks in insulation and other protection devices have not occurred during manufacture or through wear and tear."
This test method involves applying a higher than normal voltage to the product over a defined period of time. In order to pass, the product should be able to withstand this stress, thereby providing assurance that it will not fail when operating at a normal voltage.
Earth bond testing
Earth bond testing measures the connection between the ground and any metal components on the product. A high current of around 25amps is passed through, to ensure there is sufficient electrical connection, in order to protect against electrocution if there is a fault with the electrical supply to the product.
Outsourcing your electrical safety testing
If you are outsourcing part or all of your manufacturing and testing operation to an electronics manufacturing services (EMS) provider, it is your responsibility to ensure that their practices comply with the relevant electrical safety regulations.
A good EMS supplier will carry out electrical safety testing as a matter of course. Nevertheless, you should at least specify basic electrical safety testing - e.g. earth bond and flash tests - when briefing your EMS partner.
Testing is the only way to identify manufacturing faults that could compromise the electrical safety of a product out in the field. Thorough electrical safety testing protects against the risk of electrical shock, so that products can be used for their intended purpose with minimal chance of injury occurring.