Quality Assurance and Research and Development
B&D Technologies typically receives two types of requests for test stands. The first request is a way to test quality, whether it is a repair or new product about to go the customer. The second is purely research and development. The next series of blogs will outline several applications of test stands that fit into either category.
The applications generally have one thing in common. The request is a concept that rarely goes further, as far as desires and information. This example comes from a gearbox OEM that needed to test the assembled gear motors prior to shipping to their customer.
Our B&D Technologies customer needed up to 20HP at 460VAC and 10HP at 230VAC, which in itself is very easy. However, the customer wanted to use a single drive that utilized a selector switch to change voltage. The challenge was in the programming and making it wide/loose enough to not be so sensitive to variations. The goal was to easily run the motor at either voltage.
The design did not need to be high performance, so we used the ABB ACS550. The 550 allows users to program two user groups and switch between them with a selector switch that is part of the programmed digital inputs. The trick was to maximize the motor model and switch between them.
Ordinarily we advocate to never run a 230VAC motor with a 460VAC drive. Can you? Yes, of course, but we do not like to run this combination in production. Here’s why- on some occasions, SEW along with with some OEM designs like to do what they call “supercharging” on their gear motors to allow for more torque range on field weakening. They hook a 460VAC drive to the 230VAC YY winding of the motor. The problem is that when the customer had a breakdown, they hooked the new motor up to the 460VAC single Y winding because nothing was notated on the motor and/or the prints. One assumes that a 460VAC motor winding hooks to a 460VAC drive like the other 99% of the universe. The motor failed, so did the second one after they both ran at higher speeds for a hot minute before getting ugly.
Not to pick on SEW, you can do this with ABB, Emerson, Rockwell and virtually any drive on the market. Even the low cost, low performance drives of automation direct can create a rudimentary motor model to change the motor voltage and frequency characteristics.
After sitting down with the engineering folks who were responsible for the quality assurance of the gear motors, we were able to create a specification to design and build from.
B&D Technologies created a customer N12 enclosed ABB ACS550 with local controls that operated start/stop, speed reference, indication of run, and allowed the user to switch between 230VAC and 460VAC motors.
The test stand drive has now been in service for a few years and has tested thousands of gear motors prior to being shipped to customers around the world.
Test Stands fall outside the realm of normal production inside of manufacturing plants. The rules change and sometimes the capability of the system is subject to performance requirements that are not inside the normal drive manual. To ensure compatibility, we test the concept in our labs first, prior to complete proposals.
C Tolbert DOE