What is an Electrical Fault?
An electrical fault is an abnormal condition caused by equipment failure or wiring defects, causing incorrect operation of machinery or devices. Electrical faults can bring an entire production line to a halt and as a result can be very costly.
Electrical faults are typically either an open circuit or a short circuit but can also be a combination of these. Other faults may include improper operating voltage, mechanical failure of components and excessive heating or corrosion.
Troubleshooting Electrical Faults
Electrical faults are the bane of existence for every maintenance and trades professional in the industrial world. Much head scratching and creative use of language has been employed to solve electrical faults over the years! The truth is, downtime is a reality in any corporate or manufacturing environment.
Knowing how to troubleshoot effectively can make all the difference in your organization! It can help to reduce downtime!
Let’s take a look at some common faults and how to diagnose them.
Identifying Electrical Faults
- Open circuit faults are most common and are relatively easy to troubleshoot. Typically, this type of fault can be identified quickly as some part of the circuit will not be operating since it is not receiving the voltage it requires for correct operation. Look for burned out light bulbs, open operating coils and loose connection or terminal points to cause this type of fault. On equipment with wiring that continually flexes, you may find a broken conductor inside the insulation which causes an open circuit.
- Short circuit faults are more difficult to find and repair. Typically, a short circuit occurs when the insulation around a conductor deteriorates and the current finds a path to another conductor or grounded object. This can cause fuses or circuit breakers to operate because of unwanted excessive current flow. Another possibility is that the short circuit will energize other parts of the circuit and cause other components to operate unintentionally. Although a fuse or circuit breaker can open from “old age”, it is more likely an indicator of a short circuit or overcurrent situation.
- Low voltage problems can cause relays to chatter or not pick up at all. Motors and components with coils can heat up more than normal and cause electrical insulation to deteriorate and possibly fail.
- Over voltage problems generally shorten the lifespan of most components due to greater than normal heating. Lighting and motors are most affected by this problem.
- Electro/mechanical faults usually happen to components that are nearing end of life or have manufacturing defects. This type of fault includes things like a pushbutton that no longer closes when pushed or a relay with stuck/welded contacts. This type of fault often exhibits no exterior signs of internal problems.
Safety first! Before you begin to troubleshoot an electrical fault, ensure you know your organization’s safety rules and procedures, including the lockout/tagout rules and testing procedures.
To be an effective troubleshooter you must always start with a strategy, a systematic approach, if you will. To begin, gather information about the equipment and the fault including prints and manufacturer’s manuals.
Understand how the equipment is designed to operate and review documentation of the problem such as work orders, trouble reports or discussions with the person who reported the problem. Then, follow this systematic approach.
Look for visual signs of malfunctioning equipment including loose components, parts in bottom of cabinet or signs of overheated components. Don’t forget to use all your senses including smell, listening for abnormal sounds and touching to feel for excessive heat or loose components. Also, fully test operate equipment if possible and note what is working correctly and what is not.
- Define Problem Areas
From your observations decide what parts of the circuit are operating correctly and which are not. Any properly functioning parts of the circuit can be eliminated from the problem areas which will decrease your testing time required later.
- Identify Possible Causes
Once you have identified the problem area, you can now begin to list probable causes. Try to think of every possibility that could cause the problem and rate each by probability. Typically, possibilities would include the following: blown fuses, mechanical components, windings and coils, terminal connections and wiring.
- Test Probable Cause
Now that you have a list of most probable causes you can begin testing. Start with the most probable cause. Always know what to expect before you take a meter reading and know what it means if you get a reading different than what you predicted. From your tests you may need to sectionalize the circuit further to reduce the problem area. Continue with this method until you find a suspect component or wire.
- Replace Component and Test Operate
Once you have proven a component is defective, replace the component and test operate the complete circuit. Make sure you check all features and operations of the circuit. If everything is operating correctly return the equipment to service. If the circuit still does not operate correctly, you will need to rethink your logic and return to step one.
Tools of the Trade
Many tools are available for electrical troubleshooting.
A common multimeter is a great start and usually all you will need to perform most of your tests. A typical multimeter can measure AC volts, DC volts, resistance and small flows of current.
Another great addition would be a clip-on ammeter for measuring operating current.
Let’s look at what these tools do and when to use them.
An ohmmeter measures resistance in a circuit and is a great tool for finding short circuits, open coils or burned out light bulbs. Power to the circuit must be shut off and locked out before taking an ohmmeter reading and remember to put the leads together and take a reading to prove the meter is operating correctly before starting. It is always good practice to remove one wire from a component before taking a reading to ensure there are no parallel paths in your reading.
A voltmeter measures AC or DC volts in a circuit and is preferred for finding open circuits. Always check your meter on a known voltage source to verify it is working correctly before taking test readings. Try to keep one lead as a reference lead and keep it on neutral or ground. Use the other lead for picking terminals for your test points.
- Clip-on Ammeter
A clip-on ammeter is useful to measure current draw of components while they are operating. A motor that is drawing more current than normal may have worn bearings or could be overloaded. The clip-on ammeter is also useful for determining current flows in different parts of a circuit.
A Few More Tips
- Never underestimate the power of your own senses in determining faults. The “burnt insulation” smell is almost always a good indication of a failed component.
- Listening for abnormal sounds when operating a device can also lead you to a problem.
- Looking at components for visual signs of burning is always a good place to start and checking for overheated equipment can also be an indicator of trouble. Just be careful not to get burned yourself when checking for hot equipment!
Simutech’s Systematic Troubleshooting Approach
We can assist your organization in building an effective troubleshooting program. Simutech’s Systematic Troubleshooting Approach offers a 5-step method to identify the most efficient means to generate consistent, optimum results. The Simutech Training System provides a simulation-based environment to learn the troubleshooting approach, and then allows users to practice and perfect their skills on a variety of fault simulations.