By Gene Vogel
EASA Pump & Vibration Specialist
The EASA Motor Winding Workbench application is a powerful tool for service centers providing the capability to meet their customers’ needs for AC stator and wound rotor rewinding. In most cases, the data from the existing winding is recorded when that winding is removed from the core. But occasions arise where that original data is not available; it may have been recorded incorrectly, or a different service center may have stripped the core but not completed the repair. In those cases, the service center must come up with a new “bare core” winding design. Workbench has some specific features to address this need.
GO TO MOTOR WINDING WORKBENCH HELP & FAQS
The Reference Motor segment of the program is the EASA Winding Database compiled over decades from winding data submitted by EASA members. With over 250,000 winding records, it is likely that windings similar to the original winding are available in the Reference Motor database. By simply searching the database for the core dimension criteria, a list of prospective matching windings is returned. A winding from the database does not have to match the original motor nameplate exactly to be used as a basis for the bare core design. When a matching winding is selected, that data can be automatically transferred to the Workbench Motor editor where any modifications needed to match the desired criteria can be adjusted. The process is smooth and effortless and accommodates most three-phase induction motor windings.
The first step is to display a list of prospective windings that closely match the bare core dimension criteria. Enter the core length, bore diameter, number of slots and poles into the three-phase Reference Motor search bar at the right of the display (if the search bar is not visible, select the 
icon at the top right). As an example, we will search for a 125 hp Marathon with 12” core length, 14” bore diameter and 72 slots, 6 pole motor. Initially, enter only the core dimensions, number of slots and number of poles; the Motor count button at the bottom of the search bar will quickly return the number of matching records. If the result is reasonable (about 50 or fewer motors), click “Show motors” to retrieve those records into a spreadsheet format where the records can be sorted by columns and reviewed. If the Record count is too large, enter additional criteria to narrow the search. For this example, 44 records were found. Narrowing the search to the target 125 hp returns 16 records. (See Figure 1.)
Figure 1
Workbench search criteria for a 125 hp 6 pole motor.
The spreadsheet can be sorted by columns to easily review the data. It is useful to sort by the Air gap density (AGD) and Power (Pwr) columns to assess if the bare core is a good candidate for the desired resulting winding. If there are several windings with the desired power rating and the AGD is within acceptable Workbench limits, there is a high probability the redesign will be successful. For this example, there are 16 windings rated at 125 hp and ten of them are Marathon motors. So, in this case it is likely original factory data is available. Of course, that is not always the case. Suppose our bare core is a Siemens motor, which is not listed. We can still select a different manufacturer winding as the basis for our bare core design. Select one of the windings from the spreadsheet that matches the desired nameplate data as closely as possible. The full winding data will be displayed in an editor. (See Figure 2.)
Figure 2
The Motor editor displays the complete data for the selected Reference motor record.
This original data record was in the database, so no redesign was necessary; the bare core can be wound directly from
the database record. Such is not always the case, and Workbench has a function to transfer data from a Reference motor winding record to the Motor editor. The Send to Motor editor button creates a new record in the editor where all the editor redesign functions are available. Taking our example motor, suppose the desired winding is 575 volts. The available Reference motor records are only 230 or 460 volts. Figure 3 illustrates the Reference motor record sent to the editor and the volts redesigned from 230 volts to 575 volts.
Figure 3
The Reference motor record is transferred to the Motor editor where the redesign can be adjusted for 575 volts.
The final redesign is illustrated in Figure 4.
Figure 4
The 1:12 pitch with 6 turns improves the circular mils/amp.
Notice the winding is redesigned for 575 volts and the connection was changed from 6Y to 3Y to keep the Volts per Coil within acceptable limits.
The new EASA Motor Winding Workbench combines the EASA Reference Motor database and the redesigned Motor editor in a single application that’s an easy-to-use solution when presented with bare core winding challenges.
ANSI/EASA AR100
More information on this topic can be found in ANSI/EASA AR100
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