Power supply considerations: Size, application, environment
|From Control Engineering and other resources.|
Are power quality and reliability among your concerns? Are you working on a power supply retrofit project? Here are considerations, large and small, for sizing, application, and integration, to ensure minimum project disruption.
|Fluke 289 Industrial Trending Digital Multimeter has useful features like ghost voltage detection, filters for variable-frequency drive output readings, and record/save ability for V ac, V dc, Ohms, capacitance, A ac and A dc.|
A power supply system can include: Signaling module, dc power supplies, redundancy module, dc uninterruptible power supply (UPS), battery backup, and electronic diagnostic module.
Beyond just a power supply, systems now provide integrated components. Previously, the end-user, machine builder, or system integrator had to make separate elements work together. Also now commonly included are multi-color LEDs for diagnostics, relay contacts for alarming or reporting signals to higher-level controls, and power security components.
“In the past customers had to come up with their own solutions or risk downtime or maintenance issues. Vendors provided 24 V power supplies and that was it,” says Kai Bronzel, product manager for product supplies, Siemens Energy & Automation Inc. Now automation suppliers can provide everything, avoiding any consideration of office-grade UPSs for critical plant-floor applications, Bronzel says.
As for sizing power supplies, Rockwell Automation advises: 1) Determine the “average” continuous current of the load and the typical inrush current, and 2) Select a power supply where the rated load is at/or below the current of the device and the peak current is less than the short-circuit rating of the power supply.
|Supply, diagnostics, and backkup modules are in the Sitop DC Power Security System with DC UPS and Battery Backup from Siemens Energy & Automation Inc.|
Power supply failures can be big and small. Even with 24 V protection on a line, 3-phase power coming into the building can disrupt operations. To avoid this, know where troubles originate, and what they can cost before making an investment. Energy assessments, before and after outages, can justify investments in energy saving and other electrical devices.
At Fluke’s site online, see the document, “Power Quality Troubleshooting” for detailed advice on power supply failure issues. Fluke also advises the following:
Know the cost of downtime: Quantify the cost attributed to power loss or power quality to help justify any project;
Troubleshooting, diagnostics: Handheld tools with on-screen diagnostics can help get your operation back online quickly;
Predictive maintenance: Detect and prevent power quality issues before downtime happens;
Quality of service: Check incoming power quality at the main and remember that 75% of power quality problems originate with wiring and grounding (Ask yourself: How’s your isolation?);
Long-term analysis: Find intermittent power issues and map the location, keeping all related records; and
Load studies: Before adding loads, verify electrical system capacity.
Mark T. Hoske, MHoske@cfemedia.com , editor in chief, Control Engineering.
| ONLINE extra
– Ground Loops ;
– See the unseen: Power data diagnostics ;
– Power Quality Troubleshooting PDF from Fluke ;
– Fluke 289 True-rms Industrial Logging Multimeter with TrendCapture ;
– Balluff calculator determines power supply size ;
– Carlo Gavazzi interactive Power Supply Selection Guide ; and
– Sizing a power supply, from Rockwell Automation .