Are you new to Industrial Automation and are you wondering what the difference is between a motor and drive? As an Industry Professional Trainer since 2006 let me explain to you the differences.
The Motor does the mechanical pushing, pulling, lifting and hoisting so mechanical work. The Drive is an electrical controller that changes the flow of electricity to the Motor for speed and torque and they come in different types like servo and stepper drives depending on their application.
Now that you know the basics let’s look a little more in depth as to how each works.
Introduction To Motors and Drives
Whether you realise it or not you are surrounded by motors every day at work and at home. The fan on the ceiling, your washing machine and drier, your car engine, in air conditioners and refrigerators. Specifically we are talking of more industrial applications in this article where those motors are used in plants and processes.
Some examples of industrial applications of motors and drives are:
- Conveyors
- Pumps
- Fans
- Condensers
- Turbines
- Alternators
- Compressors
- Material Crushers
To understand these applications lets discuss motors and drives on their own and see how they then build into a motor drive system.
What does a Motor do?
There are two main uses of motors which are: putting electricity in to get the drive shaft to spin which is called mechanical power, or rotating the drive shaft to produce electrical power. So to simplify it we put in power and get movement of something like conveyor belts or cranes. Or using it as a power generator like in a power plant and turn a turbine (basically a fan) that is attached to the motor drive shaft to make electricity.
There are two type of electric motor and they are:
- Alternating Current (AC) Motors
- Direct Current (DC) Motor
Essentially motors use electromagnetism to produce motion and this is done with the winding wire around the shaft of the motor and turning on and off these bundles of wire to produce motion. Alternately the motion of the drive can also produce electricity as we mentioned earlier if run in reverse.
Here is a quick video that explains how the internals of a DC motor actually work:
For an AC or Induction Motor typically this is done using what is called 3 phase or three sets of power cables. This is commonly referred to as Industrial Power and is something you will see in most industrial applications. To understand this think of your power at home when you plug into the wall as a single phase. You have a positive and negative terminal on a plug and an earth in case something breaks so you don’t get electrocuted.
So if we ignore the earth on the plug for the moment we have a single phase. So now in Industrial Plants the power normally comes from the power plant as three sets of these pairs of cables. So why is having these three sets of cables important to us? Well we use them to make a 3 phase AC motor or induction motor to spin.
Here is an example video of just how this works:
What is a Turbine?
This is a mechanical device that is a motor that is made to spin to produce power. These are generally used in power plants where the movement of heated liquids moving through pipes causes that spinning motion. Wind turbines are another example of this as a renewable energy source. This is the opposite of applying power to make the drive spin.
What are the types of Motor Drives?
How can you directly connect a Motor?
For 3 phase AC or inverter motors we can have Direct On Line or Star Delta connections or motors directly to power with traditional start, stop and trip controls. There is no smarts in connected motors in this way and they apply the full power and therefore load to the motor straight away. This is generally done for motors that are not under huge load like a fan in a bathroom for instance. It is only pushing air and is only a small motor.
What is a Soft Starter for a Motor?
Essentially this is a dumb controller that slowly starts and stops the drive with minimal controls. This is critical for instance if you were at a mine site and wanted to start fully loaded conveyors that are pushing coal to a stockpile. If you tried to put full power to the motor it would blow up or burn out. This way you can slowly start the conveyors and stop them to protect the motor.
What is a Variable Frequency Drive (VFD)?
This type of drive controller can be used to change the speed and hold the speed at certain levels from 0 to 100 speed which is the Revolutions Per Minute (RPM) of the motor. It can also control the torque of the motor which is in simple terms the power or push of the motor. There is a lot more to VFD’s and we will discuss them below. VFD’s are also referred to as Variable Speed Drives (VSD). As well as being able to control speed these also allow the ability to save power by setting the motor at optimal speeds for different applications rather than fully on or turned off. They also allow for more complex control like that of Proportional, Integral and Derivative (PID) control for specialist applications.
What is a Servo Drive for a Motor?
This type of controller and drive is used for precision control that we often see with robotics or in manufacturing where there is not just speed and torque as with a VFD but also position and gears. The motor for a Servo often uses rare earth materials in its creation that provide this higher form of control over a standard VFD and motor combination.
Here is a video explaining what servo motors are and what they do:
What is a Stepper Drive for a Motor?
A stepper drive is like a servo motor that has more steps or stopping points than a standard servo drive. A servo drive will have 4 to 12 stopping points on average and a stepper motor will have 50 to 100 steps or stopping points. Stepper motors move by being given pulses of power where a servo motor compares with where it should be to where it is as a command from the drive and adjusts accordingly.
Here is a video that will explain the applications of a stepper motor:
For more info try on below links:
http://www.acontrol.com.pl/drives-control-engineering/engineering-in-automation/applications-ac-dc-drives/
https://www.motioncontroltips.com/motion-applications-dc-drives/
https://www.st.com/en/applications/industrial-drives/servo-drives.html