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Analogue to digital DC drives

01 July 2019

In the late 1980’s and early 1990’s if you wanted to vary the speed of an industrial motor the only way to do this was with a DC motor and a DC drive. It was the industry norm. But at the same time this technology was analogue. Even when the first AC inverters came along the setup was analogue. So, what do we mean by analogue?

In real terms it meant you did not have the availability of any type of chip set, so process logic such as multipliers, dividers, PID’s and all signal processing and amplification was done using discrete components like resistors, diodes and capacitors. Even with this limitation the ability to conceive advanced process circuits was still happening and, in many cases, drives companies supplying to the process control and continuous process industries were very ingenious in producing rack mounted systems to meet the customer’s needs. Even in these early days PID and winder type control was quite advanced.

As technology advanced and the microchip became available to industry the change from analogue circuitry to digital based programming started to take place. In the early days the chips were very slow and did not match the analogue performance but as Gordon Moore predicted in “Moore’s Law” the number of transistors in integrated circuits doubled every couple of years and so with it did the speed of the processing. 

Read the full article in the July issue of DPA

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