Of all the questions we are asked, this is certainly one of the most prevalent: Should we redesign an electric motor or would we be better off just repairing it? Our answer is always, “It depends.” Sometimes a repair makes the most sense. However, in many instances, you would be better off with a professional electric motor redesign.
Following are some examples of redesigns that have proven highly successful. These were all done by our company, HECO. So our views are a bit slanted. I admit though, that there are other electric motor repair shops that are also well qualified to undertake redesign.
Before you award a redesign to HECO or any other shop, it’s a really good idea to see if they ask some questions before they start giving answers (in other words, estimates). See if they ask why the motor failed? Was the breakdown unexpected or was it caused by a series of events? Was the breakdown because of the motor or something else in the powertrain? What is their lead time? Will the redesign be inspected before it’s installed? What kind of inspection?
Getting satisfactory answers to questions such as those will save you a lot of aspirin — and money.
Now, back to redesigns.
When a motor manufacturer builds a motor, they must design it to match most conditions known in the industry. They must make a motor to operate in a range of + or - 10% of nameplate data. This means the motor operates most efficiently at nameplate voltage. For example, 460vac, 3ph/60hz. We all l know that in the real world, operating voltage may fluctuate between 410vac and 510vac depending on where it is on the line or grid.
With that in mind, you should have the following info for your electric motor repair shop:
- What is your actual 3 phases of operating voltage and current?
- What is your actual horsepower requirement?
- What is the application?
- What is the history of the motor?
With this information, your motor can be redesigned to its optimum operating efficiency. This saves you energy costs, and also reduces the probability of a future failure by fitting the motor to your unique application.
No copies allowed
You will want to be sure that your shop does not just copy the original manufacturers winding data. To operate at its most optimum efficiency, a motor or generator diagnosed as a rewind needs to go through a series of engineering checks both mechanical and electrical.
At HECO, these tests include checking the laminated core to ensure that no localized hot spots are present which could cause premature failure. Then we verify the original manufacturers winding data via magnetic densities, and make engineering changes where designs are inefficient both mechanically and electrically.
Some examples of successful redesigns
- A large Michigan scrap dealer had a shredding machine with a Fairbanks 3,000hp, 700rpm, 956-30 frame, type KZBL, 4160vac, 3ph/60hz, 338amp motor. After determining the exact application and horsepower requirement, the motor was redesigned to 2,000hp, 700rpm, 4,160vac, 3ph/60hz, 259amp.
- A large Michigan automotive corporation had a 1,000 hp Allis Chalmers 1800rpm, type ANZ, 4,800vac, 3ph/60hz, 106amp motor; it was redesigned to a 1,500hp, 1,800rpm, 4,800vac, 3ph/60hz, 159amp unit.
- A nationally known surplus dealer, had requirements that lead to redesigning an 800hp, 6,346Z frame, type K, 1,165rpm, 2,300vac, 3ph/60hz, 178amp General Electric motor to a 500hp, 720rpm, 2,300vac, 3ph/60hz, 111amp unit.
- An electric motor service company had a Louis Allis 200hp, 1,190rpm, 509U frame, type CJX, 2,300vac, 3ph/60hz, 46 amp motor that was redesigned to 250hp, 1,800rpm , 2,300vac, 3ph/60hz, 56.5amp.
- A large utility company in Michigan, due to economic reasons, switched over to western coal. This put additional loads on their pulverizer and fan motors. To optimize the additional load, HECO redesign seven units. Five were 400hp, 885rpm, 3,321 frame Elliott motors at 2300vac, 3ph/60hz, 100amp. They were redesigned to 450hp, 885rpm, 2,300vac, 3ph/60hz, 113amp.
Two Louis Allis 450hp, 1785rpm , 769SU frame, type WPX , 4000vac, 3ph/60hz, Samp motors were converted into 500hp's at 1785rpm , 4000vac, 3ph/60hz, 61amp units.
Those are but a few of the virtually unlimited ways an electric motor can be redesigned for optimum efficiency. To learn more about what our “All Systems Go” approach can mean to your next redesign, please contact:
About the author:
Justin Hatfield is Vice President of Operations of HECO, Inc. He is responsible for Electric Motor & Drive Sales, Electric Motor & Generator Repairs, and Predictive Services. Justin was instrumental in developing HECO MAPPS (Motor And Powertrain Performance Systems) which focuses on “why” you have a motor problem instead of simply “What” product or service should be recommended. HECO is EASA Accredited.