Throughout the weeksthe lesson that I found the most interesting was week 7 where Mo explained thedifferences between AC/DC motors. The reason I found this so interesting wasI’ve liked and enjoyed being around vehicles all my life.Taking components apartto the last piece is one of my favorite things to do, this is because I like tofind out how everything works together and why it’s constructed the way it is.Nikola Tesla was thefirst person to invent and construct the first induction motor.
This was backin 1887. Nikola first began to experiment in 1888. He owed his own experimentalshop in New York.
Nikola Tesla was born in Croatia on the 10th July1856. He immigrated to the United States of America in the early 1880’s. Frank Julian Spraguewas the first person to invent the first practical DC Motor. This motor workedwas a non-sparking motor that worked under variable loads without the change ofspeed. Frank Julian Sprague was born one year later than Nikola Tesla. UnlikeNikola Tesla, Frank Julian Sprague was born in the United States of Americawhere he attended the United States Naval Academy where he was very successfulin mathematics which led him to graduate 7th out of 30+ otherstudents. AC MOTOR- Induction Motor Most homes, factoriesand offices are supplies alternating current which has a frequency of around50hz.Parts · Stator · Rotor · Bearing· Frame-yoke · Cooling fan · End bracket· Stator windings· Drive shaft· Magnet The induction motor has two main parts thestator which is stationary and the rotor which rotates.
The stator is athree-coil winding and three-phase AC power input is supplied to it. Thewinding passes through the holes of the stator these holes are made by stackingquite thin permeable steel laminations; these laminations are usually insidecast iron or a steel frame. When a three-phase current passes through thewindings it creates a rotating magnetic field. The turning speed of themagnetic field is known as the synchronous speed. According to Faradays law becausethe magnetic field is varying an EMF will be induced in the loop. An EMF will produce a current in the loop,according to Lorentz law when an electromagnetic field is produced on the loopthis will cause the loop to begin to rotate.
This same sort of process happensinside a three-phase, squirrel cage, induction motor. The three-phase AC current passing throughthe stator produces a rotating magnetic field. Current will be induced in thebase of the squirrel cage, which is shorted by the end-rings. This will causethe motor to commence to rotate. This is the reason why this type of motor iscalled the induction motor because electricity is induced on the rotor withavail of electromagnetic induction rather than a direct connection. The availsuch electromagnetic induction insulated iron core laminas are placed insidethe rotor.
Tiny sizes of iron ascertain that Eddy current losses arekept as low as possible. The induction motor has a quite big advantage as it isself-starting. Induction motors rule both the domestic and industrial worlds.
An induction motor does not require a permanent magnet. They do not evenrequire brushes, commutator rings not even a position sensor unlike a dc motor.The speed of an induction motor can be controlled by changing the input power. DC MOTOR A DC MOTOR speed can be changed bychanging the supply voltage or by changing the field winding current. A DCMOTOR uses power directly from the battery. Parts· Stator· Poleshoes · Fieldwindings · Armaturewindings · Armaturecore · Bearing· Shaft· Commutator In a DC Motor the stator provides a constantmagnetic field, and the armature which is a simple coil is connected to a DCpower supply through a pair of commutator rings.
When the current flows throughthe coil an electromagnetic force is induced on it according to the Lorentzlaw. This means that thecoil will begin to rotate. As the coil rotates the commutator rings that areconnected to the DC power supply have opposite polarity. This results that onthe left side of the coil the electricity will always flow away, and on theright side the electricity will always flow towards. This ensures that thetorque action is also in the same direction throughout the motion, this meansthat the coil will continue to rotate.
But if you look at the coil actionclosely you will notice that as the coil is nearly vertical to the magneticflux the torque action is approximately zero. This result is irregular motion of the motorthat’s if you chose to run this sort of dc motor. On the other hand to overcomethis problem more loops are added to the motor with a separate commutator pair.With this sort of arrangement as the first loop is perpendicular to themagnetic flux, the second loop will be connected to the power source so themotor force is always present in the system. The more loops you add to themotor the smoother the motor rotation.
In a practical motorthe armature loops are fitted inside slots with highly permeable steel layersthis will result in the enhancement of the magnetic flux interaction. Springloaded commutator brushes help to keep the contact with the power source. Apermanent magnet is used is smaller DC motors.
Most often an electromagnet isused, the field coil of the electromagnet is powered from the same DC source.The field coils can beconnected to the rotor windings in two different ways which are in parallel orin series. The two main differences are that the motor connected in serieswound motor has very high starting torque but once you apply load the speedwill drop drastically. On the other hand the parallel motor also known as theshunt motor has a low starting torque but when load is applied the speed of themotor remains constant.
Brushed-BrushlessDC Motor Parts BRUSHED DC MOTOR PARTS BRUSHLESS DC MOTOR PARTS Stator magnets Stator Windings Windings Brushes Permanent magnet Positive and negative terminals Rotor Commutator Bearing Armature BRUSHEDDC MOTOR ADVATAGES AND DISADVATAGES AdvantagesOne of the main advantages of a brushed DC MOTOR is that itis easy and very cheap to produce. It is very simply built.DisadvantagesOn the other hand it does require a lot of looking afterdue to the wear on the brushes. BRUSHLESSDC MOTOR ADVATAGES AND DISADVANTAGESAdvantagesA brushless DC Motor has a big advantage over the brusheddc motor which is that it is highly efficient and does not require as muchmaintenance. It has a higher output power.DisadvantagesThe main disadvantage is that it is very expensive toproduce and reproduce. They also require electronic components to control anddrive them. Induction-synchronousmotors INDUCTION MOTOR PARTS SYNCHRONOUS MOTOR PARTS Stator Stator Rotor Rotor Bearing Bearings Rotor windings Magnet ACINDUCTION MOTOR ADVATAGES AND DISADVATAGES AdvantagesAn ac induction motor is self-starting; this is a goodadvantage as it does not need a direct power source.
Unlike the brushed dc motorit does not need as much maintenance to keep it running. It is highlyefficient. DisadvantagesOne of the disadvantages is that you cannot change thespeed of the induction motor as easy as they are pretty much running at oneconstant speed. Synchronousac motor advantages and disadvantages AdvantagesA synchronous ac motor does not require a dc power for therotor excitation they also require rotor windings unlike the induction motor asan induction motor uses a squirrel cage.DisadvantagesSynchronous motors will not start at load the motor has tohave zero load applied to it for the motor to be able to start.
The kilowattpower output costs more to produce rather than an induction motor. Electriccars- Tesla model SThe powerhouse of the Tesla car is invention by NikolaTesla. (For more information about Nikola Tesla you can read the introductionto this assignment). The Tesla model s is ran by an induction motor whichNikola Tesla discovered. The induction motor has two main parts the stator andthe rotor.
You can find more information on this motor on page 4-5. The rotor is basically a collection ofconducting bars which is short circuited by the end rings. A three phase accurrent in the coil creates a magnetic field. The Tesla model s produces afour-pole magnetic field. This turning magnetic field induces rotor bars tomake it turn; the induction motor is robust and powerful. The induction motorspeed depends on the frequency of the ac power supply. Just by changing thefrequency you will be able to change the speed of the vehicle road wheels.
Thisknown fact makes car speed very controllable and reliable. The motor speed canrange from zero to 18,000rpm, this is the most sizeable advantage that electriccars have compared to internal combustion cars. An internal combustion engine produces usable torque andpower output only within limited speed range. Therefore, connecting the enginerotation directly to the drive wheel isn’t the best idea. That’s why atransmission is put in to vary the drive wheel speed, where as an inductionworks efficiently at any speed range. Therefore no speed varying transmissionis needed for an electric car.The power output of an internal combustion engine is alwaysuneven many accessories are needed to overcome this issue.
Where as you will get direct rotationalrotation motion and power output with an induction motor. Many part, componentsare simply removed which makes the engine lighter compared to a compared to a combustionengine. As a result of doing this you will get a higher power to weight ratiomaking the vehicle faster lighter and more environmentally friendly.Advantagesand disadvantages of electric cars ADVANTAGES DISADVATAGES No emissions Expensive No sound No sound- people can’t hear them coming Safety features Low drive range per charge Expensive ConclusionIn conclusion, I really enjoyed the AC and DC topic, thisis because it got me more inspired to learn more about the different variety ofmotors that the previous and the current generation still use; this is becausemost of them are so easy to produce and relatively cheap and very reliable.
This subject was very interesting just learning about how motors change andhelp today’s world to produce electricity for big and small cities andvillages. This topic didn’t just teach me this but it also taught me that a lotof stuff look more complicated than they are.