Dear Mark, Please take a look at the picture positive.gif attached. The electromagnetic coil is a pump sucking the flux at one end and pushing it to the other end. You may note that blue coils are pushing the flux from the left to the right. The stream could not abruptly stop. It should return back to the sucking point. The returning path is marked with blue letters (in between the coils) But the green coil also sucking the flux and resist the returning flux. It might be more effective if we change the polarity of the green coil. That is shown on the picture reversed.gif. I have simulated both cases and got the results opposite to what I was expecting: Positive orientation, focus point force/weight ratio 18.4. Reversed orientation, focus point force/weight ratio 7.1 (I thought it should be higher then in the first case). That makes me think of another explanation. The reversed coils provide short-ranged paths for the flux. That is the flux easily finds a _short_ returning path. The flux density inside the coil is high, but fades rapidly with distance. The positive polarity coils prevent the flux from returning back to the coil. So the flux flows further away. Time spent 1 hour. Best regards, Alex ------------------------------------- Aleksandr Liubimtcev QuickField Support team http://quickfield.com e-mail: aleksandr.liubimtcev@quickfield.com On 13.11.2018 17:53, Mark Arokiaraj wrote: > Dear Alex, > > So far we have the best results with 15 x 15cm 7 x 7T coils. > We will see back-to-back as shown below. > > with regards, > Mark