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By David Rosenfield, Malcom Frederick and Winn Hardin
Electric motors for industrial and commercial applications come in countless sizes and shapes spread among various types, including AC induction, AC synchronous, wound-rotor, multispeed, inverter-duty and DC motors. Each is available in a range of speeds, enclosures and mounting configurations. One common theme is that each requires a control system that incorporates separate power and control circuits.
Recent generations of NEMA-rated controls are robust, which makes them perfectly suited for reapplication if they’re no longer needed for their current use. They’re usually good candidates for repair and reuse when reconditioned by qualified technicians following qualified standards.
Qualified service shops follow reconditioning standards promulgated by the Electrical Apparatus Service Association Inc. (EASA, www.easa.org). It’s important that you inspect and qualify any service shop before you send your equipment for repair. Be sure that you know the vendor and its capabilities.
The Professional Electrical Apparatus Recyclers League (PEARL, www.Pearl1.org) standards are split into three categories: full reconditioning (Blue Seal), test and inspection (Green Seal) and inspect-only (PEARL Stamp). Test and inspect (Green Seal) standards include procedures for testing and inspecting equipment to a minimum quality standard to ensure it’s safe and in operable condition. This standard was developed to meet the need for quick shipments and to maintain the equipment validation process for used electrical equipment. Reconditioning standards include Test & Inspect procedures as well as equipment reconditioning steps and additional testing.
The inspect-only standard (PEARL stamp) applies to items where no reconditioning or testing is to be done, other than cleaning or applying surface coating on the product. For example, enclosures, fittings, conduits and terminals undergo little reconditioning and virtually no testing other than visual inspections. Most dealers in these markets only trade in unused product. PEARL standards allow for quick transactions between reconditioners, enabling one shop to buy product needed for its customer with the comfort and knowledge that the product has already cleared major function and conformity hurdles and is ready for a full reconditioning.
Figure 1. The “power circuit” is located at the top of the ATRV schematic; the control circuit is at the bottom.
Let’s focus on the key steps in reconditioning a motor-control bucket (Figure 1), as well as tips to consider if you’re performing the reconditioning in-house or selecting a qualified vendor to perform the service. You should know about the reconditioning standards relevant to an autotransformer-reduced voltage (ATRV) starter, a common form of motor control for AC induction motors 60 hp and larger.
The first step a PEARL-qualified technician takes when reconditioning a control system is to remove visible dirt and debris from the interior of the enclosure as a prelude to careful inspection of the wiring harness and its connections to other components. The technician takes special care when removing the dirt and debris from the interior and looks for signs of broken parts and wear debris among the dirt, cracked and frayed wires, and cracked component cases, especially at terminal or connection points. The technician seeks out discolorations that might indicate overheating and arcing that would indicate shorts. Often a system will have maintenance notes about previous problems or settings that might provide valuable data to locate or resolve the situation. Many times you’ll find the equipment is being used outside its design capability or contains underrated devices.
After visually and mechanically inspecting each and every component, inspect the circuits, treating each as a single device. Energize and test them to ensure operational integrity. A system test verifies every component is functioning in coordination with others and ensures system integrity.
Reconditioning begins with choosing the correct PEARL technical standard, which are available as free downloads (www.Pearl1.org). These standards include forms for documenting test results, comprehensive reconditioning procedures, specification tables, and inspection, observations and procedures for each component or circuit.
PEARL reconditioning standards have two sections: recondition evaluation and recondition procedures. Both require specific calibrated test equipment (megohmmeter, digital low-resistance ohmmeter (DLRO), millivoltmeter, etc.), which are listed at the beginning of each standard. Both sections require PEARL members to use the provided forms to record test values and technician observations. Document the reconditioning process with comprehensive test results that are kept on file for future reference and supplied with each device. This is a vital part of reconditioning electrical equipment safely.
If all the procedures are followed diligently, the reconditioned device will operate as well or better than it did when it rolled off the production line. We say better because whereas new electrical equipment typically is tested in batches, reconditioned equipment is 100% tested and fully documented. This ensures the product performs at the highest performance level and can protect the vendor, electrician and end user. If the technician is PEARL-certified, follows the PEARL recondition standards, records all data, and documents the work, then a device will merit the PEARL reconditioned Blue Seal.
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