This chapter will be focusing on troubleshooting common problems found in the power and control circuits. Troubleshooting motors and the mechanical systems they drive is an extensive topic beyond the scope of this text.
A motor may not start for a variety of reasons. Knowing what to check for and where to begin is a valuable skill that can reduce downtime when a fault occurs.
Usually, there are two fundamental steps in troubleshooting. The first is a cursory visual inspection, followed by a more in-depth examination with testing equipment and referencing several diagrams
Motor control circuits have several protective devices built into them to protect wires and equipment. It is always a good idea to start your visual inspection by checking overload and overcurrent devices. A visual inspection sometimes quickly locates a fault or identifies situations requiring maintenance. For example, you might see a tripped indicator on a circuit breaker, switch or overload relay. Resetting the device might be all the circuit needs to resume working.
If an overload or overcurrent situation has occurred, it is advisable to find the source of this fault. A visual inspection can identify burnt or heat-discoloured components, loose wires in terminal blocks, or mechanical parts that bind together or cause excessive friction.
When there is no obvious cause for the problem(s), it is often necessary to analyze circuit diagrams and take measurements of voltage and resistance at key points of the circuit. To do this, we use voltmeters and ohmmeters. A firm understanding of their use and limitations is necessary for their safe operation in circuits.