McMaster UniversityPage 1 of 3

Power Electronics LaboratorySafety Precautious

Safety First: Execution of Lab work in a safe manner is even more important than performing accurateelectronic measurements and construction neat circuits. The first step is always to become familiar withthe Lab itself. You should know where the fire extinguishers and the emergency exits are located. Equallyas important is the location of nearest phone to call for help. You should also know all equipments andsubstances that are used in the Lab to take the necessary precautions.

1 General Rules

∙ Safe practices and procedures are of utmost importance in this course. Students are required to read,acknowledge and at all times obey by all safety procedures within the lab.

∙ Keep work areas clean and neat. Components and leads must be placed at their appropriate placesonce used.

∙ No food or drinks allowed in the lab.

∙ Listening devices are prohibited i.e. no hand phones, walkmans (Walkman?), iPods, etc.

∙ Preparation for the lab is important in order to know what is expected out of you during the lab.

∙ Attached you will find a listing of minimum safety practices which must be practiced in the lab atall times. These are also basic safety practice requirements. Additional instructions and informationwill be necessary from time to time.

∙ Read the attached safety guideline.

∙ Your cooperation and attention to these safety procedures are expected and appreciated.

∙ The precautions are for your protection and that of others.

2 Safety Tips for Power Electronics/Machines Laboratory

1. Do not energize a circuit before it is checked by the instructor.

2. Never handle live circuits.

3. If anything in a circuit has to be changed, switch off the power supply first.

4. Do not touch any insulated part of an energized circuit, unless it is absolutely necessary.

5. Always make connections from the load toward the source of power. Connect the power source last.

6. Disconnect the source of power first.

7. Always used the bench supply with installed circuit breakers, never use the power line as a supply.

McMaster UniversityPage 2 of 3

8. Check current connections to make certain they are tight. Loose connections can be dangerous aswell as giving erroneous experimental results.

9. Never open a life circuit.

10. Never open the secondary of a transformer if the primary is energized.

11. Disconnect the clip end of the potential leads when changing meter function.

12. Set rheostats for minimum current (i.e., maximum resistance) before energizing the circuit (Exceptwhen it is stated oppositely in the procedure).

13. Always set variable voltage supply to minimum output voltage before switching them on.

14. Do not allow leads to lie on the ground.

15. Do not allow leads to touch rotating parts.

16. Keep neckties, loose clothing, etc., away from rotating parts.

17. Make sure that couplings are always covered by their special coupling guards.

18. Assume that capacitors are charged. Discharge them through a resistance before removal from storageand before disconnecting from a circuit.

19. The green and yellow lead is the ground lead. Use them to connect the ground of the machines anddifferent components in your test set to the main ground point on the bench. Never use these leadsfor live connections.

3 Safety Rules and Suggestions

Freedom from preventable accidents is an important measure of the foresight and capability of supervisionin the engineering industries. The student should give thought to the subject of accident prevention earlyin his or her training. He or she should prepare mentally to recognize and avoid dangerous situations, andto cope with emergencies. A set of rules cannot be made to apply to all situations. The student shoulddevelop the ability to analyze a particular situation. An engineer’s reputation for reliability is seriouslyinjured if his lack of foresight results in injury to himself, associates, or equipment.

1. Haste causes many accidents. Work deliberately and carefully. Verify our work as you go along.Good planning before coming to the laboratory will promote safety.

2. When working on live electrical apparatus, use only one hand as far as practical, keeping the otherhand disengaged from circuitry. All power circuits are dangerous. Adjustment of energized circuitsshould be made with caution. Do not permit any part of your body to complete a circuit.

3. Close power switches quickly and positively. Hesitant closing may result in an electric arc. Burnsfrom an electric arc may be severe and slow-healing. You can depend on the circuit breakers andfuses in the circuit to prevent over-currents.

4. Be careful to keep watch bands, rings, necklaces, and other metallic objects out of contact with liveparts when working around electrical apparatus. It is a good idea to remove watches with metalbands while working in the laboratory.

McMaster UniversityPage 3 of 3

5. Long hair should be ”up” when working around rotating machinery. Likewise, loose clothing, neckties,etc. should be avoided around rotating machinery.

6. Make sure the plugs fit snugly in their sockets. Sometimes they get old and worn so that they slideout too easily. Never splice two un-isolated plugs together so that electrically ”hot” metal is exposedon the bench. Try to arrange your test bench in such away that you do not need too long leads. Incase that you still need longer leads use isolated-tip leads. As much as possible, use the isolated-tipsleads for power circuits, and the unisolated type for measuring voltages or signals.

7. Never connect leads so that they hang above rotating parts of equipment. Use leads long enough tohave some slack. Avoid long, unsupported spans.

8. When wiring a circuit, always connect to the source of power as the last step. When disassemblinga circuit, disconnect from the power source as the first step.