Hi Mate

From what I understand the theory of electronic motor controllers will differ in one sense. Such as Standard DC series wound motors would require contactor's for the drive system either switching fields or armatures depending on the controller and truck make.

The Seperately excited motor controllers would not require contactors. However the overall theory of operation for each type would be similar in most cases for the respective type of motor. When I usually strip down controllers for repairs it is easy to identify the circuits and their functions because the basics and functions are near enough the same.

Then you have the AC motors which are more common these days, and its theory of operation seems to be similar no matter what truck type. Saying that I have noticed that most controllers on these type of trucks are manufactured by a few companies as most AC controllers I have come across are Zapi, Danfoss and Linde and Jungheinrich's own.

These 3 being the most common motor types found on most electric forklifts.