Upon researching in the markets, you will come across several names in terms of variable speed drives and here in this post, we will be reviewing the top types. However, before that…one thing that needs a mention here is that each of them can be further divided into several parts and different variations. One similarity among all of them is that all of them will include an electric motor and a speed control unit.
In the past one decade, there has a huge transformation in the technology used in these drives and these modern-day drives mainly consist of solid state electronic components in a single system. On the other hand, if we notice their older versions, you will come to know that these drives mainly used mechanical system and this resulted into system failure because of worn out parts most of the times.
DC Motor Drives
- The first thing to know about this version is that it is also given the name of DC Motor Speed Control Systems.
- In this version, the speed is directly proportional to the armature voltage and the same is inversely proportional to the motor flux.
- Another very important point to know is that either armature voltage or field current can be used to control the motor speed.
- Most types of DC motors have become technically more advanced these days and thus, more expensive too as compared to the traditional versions and they are now actually, retrofitted by AC motors or AC drives too.
- The good thing about AC drive variable is that it is very less expensive as compared to DC system, is more available and is more efficient than DC systems.
Eddy Current Motor Drives
- According to the sellers of vacon drives, another very popular version of variable speed drives present in the markets is given the name of Eddy current motor drives.
- This Eddy current drive consists of a fixed speed motor and an Eddy current clutch and this clutch actually contains a fixed speed rotor as well as an adjustable speed motor.
- However, both these types of motors are totally separated from each other and there is a direct current in the field coil that produces a magnetic field that determines the torque transmitted from the input to the output rotor.
- There is a controller as well and its main job is to provide the closed loop speed variation and it does this by varying the clutch current.
- This actually allowed the clutch to transmit the sufficient quantity o torque that is needed by it to operate at the desired speed.
- In this type, the speed related feedback is provided by an integral AC tachometer.
- An important fact to know about this version is that it is less efficient as compared to all other types of drives and therefore, most of them are totally obsolete these days.
- However, still some manufacturing units and facilities across the globe, use this kind of variable speed drives, but they have to bear huge expenses in case of equipment failure.