Up Time Magazine- February/March 2008

Maximum Full Load Current for 3-Phase Motors with Maximum of 12 Leads (In Amperes) 45 70 110 160 250 400 600 Terminal Box Cover Opening Minimum Dimension mm 65 84 100 125 150 175 200 in 2.5 3.3 4.0 5.0 6.0 7.0 8.0 Useable Volume Minimum cm3 595 1265 2295 4135 7830 13,775 22,255 in3 36.4 77 140 252 450 840 1540 Typical Maximum Horsepower 3-Phase 230 Volt 15 25 40 60 100 150 250 460 Volt 30 50 75 125 200 300 500 Figure 2 - Terminal Housings, Motors Over 11-Inch Diameter An area of concern is where conductors enter the motor connection box. This is covered under the NEC Article 430.13: “Where wires pass through an opening in an enclosure, conduit box, or barrier, a bushing shall be used to protect the conductors from edges of openings having sharp edges. The bushing shall have smooth, well-rounded surfaces where it may be in contact with the conductors. If used where oils, greases, or other contaminants may be present, the bushing shall be made of material not deleteriously affected.” The common methods used to make the connections, themselves, are crimped lugs with appropriate sized one or multiple-bolthole connection points or split bolts. In both cases, the connections must be tightened to the requirement for the fastener, or at least 7 lb-in (0.8 N.m). Sharp edges must be removed and the fasteners should not extend far beyond the lugs so that they do not penetrate the splice insulation. The fastening system for lugs should also include washers and a lock washer to ensure that they do not come loose. Crimped connections should not be soldered or tinned, per the NEC, unless the fastening method requires it. savings involved in the installation of the pre-fabricated splicing systems. While the kit may cost upwards of twenty times the cost of electrical tape, the time savings involved is substantial, ensuring a quick and reliable return to operation. The average time for all three pigtail splices is 5-10 minutes versus up to 30 minutes for the properly insulated standard taping system. In addition, should the motor require disconnection, these splicing systems are removed far more quickly than tape, without the requirement of cutting the leads and feeder conductors. The difference in cost is quickly recovered in labor alone, not including the quicker return of equipment to normal operation and the availability of that labor for other tasks. Taping Splices In the December/January issue of Uptime, the article described failed splice insulation systems, which consisted of crimped insulated lugs and vinyl electrical tape-only insulation systems. This is of primary concern as we often see electricians carrying only the vinyl electrical tape in their kits. The other issue is the size of the splice insulation system when taped. Some have almost no insulation on them while others will be a fist-sized ball of tape. When pigtail-splicing kits are not available, taping systems can be used as a method for insulating your connections. However, the proper method of taping requires three types of tapes to be applied: 1. Varnished cambric – preferably non- Splicing/Connection Kits One of the reasons why many organizations do not use splicing kits is the cost. For electric motors, the common name for connection box splices is a ‘pigtail splice.’ These usually consist of sealing strips and slip-on rubber boots that are sized by the feeder and motor lead sizes. The key is the time www.uptimemagazine.com 59 http://www.alignmentsupplies.com http://www.uptimemagazine.com

Table of Contents Feed for the Digital Edition of Up Time Magazine- February/March 2008

Up Time Magazine- February/March 2008 Contents Upfront Upclose: Lessons Learned from the Walter Reed Story Information Technology: Parenting and Asset Performance Infrared: It's Alive! Lubrication: A Sense of Change Maintenance Management: PdM, Standardized Motor Testing: Being Well Connected Precision Maintenance: How to be Marketable Reliability: The Voyage of Wells Dairy Ultrasound: Two is Better Than One Vibration: Diagnosing a Cracked Shaft Upgrade: A Different Kind of Journey

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