What is the famous electrical machine used in control systems?

I used same question before in the usage of  frequency inverter - if I am correct

I cannot say for one machine only, but most fo control mechanism is now depends on Electrial machines.

VFD, motors, generators, PLC, DCS etc all come from electrical contol family.

If you mean by  machines the motors, generators and transformers - as the terminology is use in Electrical engineering arena, then the most used electrical machine in control systems is the stepper motors, servo-motors(AC&DC), AC/DC motors. As these devices are used as final control devices in most machine control and process control.

  the servo motor from motor family >>> and the (( plc (( from  programables >>>  

a lot of components are the family members of electrical control,some of them are,

1-sensors/limit switches/analog devices etc works as the eyes or to collect information (which are connected with inputs.

2-cpu/plc/cnc/dcs or the relays contactors data proce components analyze the instuction from inputs and genrate the output commands (as per your logic )

3-vfd /actuartors /belts rams/valves act upon commands from the No:2  to fulfil the task.

inshort the control is like a human body  with Ai(which is created by you.

Ward Leonard Control

v

contactor      overload       relay     and breaker

The DC servomotor

stepper and servo motor