When electrical anomalies during startup and testing make it seem as though poltergeists are at work, the problem can often be traced to electromagnetic induction issues created during wire installation. Induction can be easily avoided simply by following good wiring practices.
Electromagnetic induction occurs when lower-voltage cables are within the magnetic lines of flux of higher-voltage cables, inducing voltage into the lower-voltage cables. High and low voltage wires should be separated by at least 6 inches, as should discrete wires and analog wires. Lesser-skilled electricians often set off inadvertent glitches by mixing cables in control cabinets and Panduit trays. Wire intermixing is a notorious source of problems in variable frequency drives. Also, in addition to proper separation of wires, it is important to use the right type of wire for your application. Substituting twisted, shielded analog wire for jacketed discrete wire, for example, can induce voltage and cause problems.
Any time an electrical issue brings to mind words like “weird”, “odd”, or “bizarre”, induction should be considered a prime suspect. Unfortunately, induction problems usually aren’t apparent until abnormalities occur at startup, so it is important to maintain proper wire separation from the outset to avoid the headache and expense of diagnosing and correcting the issue.
Omni Instrumentation Services, Inc. is a premier instrumentation and electrical contractor, providing superior total care solutions since 1986. Services include instrument installation, tubing installation, instrument calibration, control loop testing, startup and commissioning, power and lighting, process control wiring, BMS wiring, telecommunications and data wiring, fire alarm wiring, security wiring, process network wiring, and control panel fabrication. Omni Instrumentation Services, Inc. is certified in Foundation Fieldbus, Profibus, DeviceNet and ASI-Bus installation.