Safety considerations when working in power electronics

Please carefully go through this before doing any experiments in power electronics/motor controls lab.

To minimize the potential hazards, we will use DC power supplies that never exceed, voltage of 50 V and current of 10 A. Despite this precaution, power-electronic circuits on which the student will work may involve substantially larger voltages (up to hundreds of volts) due to the presence of large inductances in the circuits, and switches which may at times break a large current.

  1. Electrical shock can kill.

  2. Exploding components (especially electrolytic capacitors) and arcing circuits, can cause blindness and severe burns.

  3. Burning components and arcing can start a fire.

  1. When working with voltages over 40 V or with currents over 5 A, always have at least two people in the lab.

  2. Use only isolated power sources, either isolated power supplies or AC power through an isolation power transformer, which will allow using a grounded oscilloscope and reduces the possibility of completing a circuit through your body or destroying the test equipment.

  3. Check for all circuit and scope connections before powering the circuit, to avoid shorting or any ground loops, which may lead to electrical shock or damage equipment.

  4. Initially, start testing with a low voltage source and low power. After the operation is proven, increase voltage and power, stopping at frequent voltage levels to check for hot components and electrical noise that can affect the circuit operation.

  5. Keep high voltage parts and connections out of the way from accidental touching and contact to test-equipment or parts connected to other voltage levels.

  6. Keep the work area neat:

    1. No loose wires or metal pieces, which can cause shorts and sparks.

    2. No long wires, to avoid getting in the way while adjusting or changing test leads.

    3. No paper near circuits, to prevent the possibility of catching fire.

  7. Wear safety glasses when operating at high power or high voltage.

  8. When working with an inductive circuit, reduce voltage or current to near zero before switching open the circuit.

  9. Remove power to the circuit before changing connections.

  10. Discharge all high voltage capacitors before making changes to the circuit.

  11. Be aware: bracelets, rings, metal watch bands, and loose necklaces conduct electricity and can cause burns. Do not wear them near an energized circuit.

  12. Loose articles may get lodged into and get pulled by the motor shaft. Ensure that the safety enclosure is closed and always maintain a safe distance from rotating components

  13. Use rubber floor mats to insulate yourself from the ground while working in the lab.

  14. Recommended: Learn CPR and keep up to date. You can save a life.

  15. Be sure about the locations of fire extinguishers and first aid kits in the lab.

  16. When working with energized circuits, while opening switches and adjusting controls and test-equipment, use only one hand, keeping the rest of your body away from conducting surfaces and your other hand in your pocket.

  17. Double-check your wiring. It is a good idea to use a point-to-point wiring diagram to review when making these checks.

  18. A switch should be included in each supply which, when opened, will de-energize the entire setup. Place these switches so that you can reach them quickly in case of emergency, without reaching across hot or high voltage components.