Last time we got a lot of questions about our Magnesium alloy wheel hub motor conversion kit, so today we are here to tell you every detail about it.This full conversion kit will provide you with an ability to transform your existing bicycle into the electric one.
Our technical department is cool as always so we are here again with our new short post about PMDC Motor.
Don’t procrastinate – read it 😉
We already wrote about Flemming’s left hand rule, but perhaps, there are new readers who didn’t read our previous post, so we’ll shortly explain it again.
Flemming’s left hand rule– this rule is applicable for d.c motors. The rule states that, whenever a current carrying conductor is placed in a magnetic field, a force acts on the conduct in the direction perpendicular to both, the current and the magnetic field.
Since all D.C motors work on Flemming’s left hand rule, it’s essential to establish a magnetic field.
This magnetic field is produced by the means of magnets.
When permanent magnets are used to create the magnetic field, the motor is called a Permanent Magnet motor or a PMDC motor.
Construction of PMDC Motor:
STATOR – is a steel cylinder with permanent magnets placed at the inner periphery of the steel cylinder.
The magnets are placed so that the alternate poles of the magnets are facing the armature or the rotor (i.e if the north pole of one magnet is facing the rotor, the south pole of the next magnet will be facing the rotor).
ROTOR- is made of varnish insulated, slotted circular laminated steel sheet. The rotor consists of core, winding and commutator.
Carbon or graphite brushes are places with spring pressure on the commutator segments to supply current to the rotor.
Working principle of the PMDC Motor:
As mentioned earlier, the D.C motor works on Flemming’s left-hand rule, when the current carry conductor comes inside a magnetic field, it experiences a mechanical force which is governed by the left-hand rule.
The armature/ rotor is placed in the magnetic field of the permanent magnet(i.e the stator); the armature rotates in the direction of the generated force.
The conductors on the armature experiences the mechanical force of F = B.I.L Newton, where
B = magnetic field in tesla;
I = current in Amperes;
L = length of the conductor in meters;
Each conductor experiences forces and the compilation of these forces result in torque, because of which the armature rotates.
Advantages of PMDC Motor:
No need for field excitation arrangement
No input power is used for the excitation of the field, thus increasing the efficiency of the motor.
No field coil, thus the size of the motor is small.
Cheap and economical for fractional kw application.
Disadvantages of PMDC Motor:
There is a chance of getting the poles permanently demagnetized (partial) due to excessive during starting, overloading and reverse the condition of the motor.
The magnetic field is present all time, even when the motor is not being used.
A pmdc motor has a lower induced torque per ampere turns of armature current than a shunt motor of the same rating.
Applications of PMDC Motor:
In automobiles for windshield wipers and washers, air conditions, for heaters, to raise the lower windows, etc.
In electric bikes
In toy industries
Used in electric tools like drilling machines, hedge trimmers, etc.
For more educational articles and products reviews subscribe on our blog and follow us on facebook.
In the 1st part of our BLDC Motor Basics post we promised you to provide information about the BLDC motor principle of work, about improving the performance of it and the BLDC motor types. We appreciate our readers and we keep our promises, so here it is – read, learn and enjoy 😉
Working principle:basic interaction between a permanent magnet(rotor) and an electromagnet(stator).
Consider three stator coil winding arrangements A, B and C. When coil A is given a dc supply, it gets energized and becomes an electromagnet.
The opposite pole of the rotor gets attracted to the stator(opposite poles attract). As a result, the rotor pole moves near the energized stator.
As the rotor nears the coil A, coil B of the stator is energized. Similarly, as the rotor nears coil B, coil C is energized. After that, coil A is energized with opposite polarity.
This process is repeated, and the rotor continues to rotate.
Improving the performance of the BLDC motor:
Problem – as seen above, only one coil is energized at an instant. The 2 inactive coils greatly reduce the power output of the motor.
In order to avoid that, energize coil B with the same polarity as coil A, when the rotor is in the position with coil A.
In this way, the combined effect will push the rotor and produce more torque and power output from the motor. The combined force also makes sure that a BLDC has a beautiful, constant torque nature.
To energize the 2 coils at the same time, the free ends of the coils are connected together.
Electronic controller unit:
An ECU is used in a BLDC motor to determine the position of the rotor and to energize the coils accordingly.
The Hall-effect sensor is used to sense the position of the rotor.
This sensor gives information to the controller, which energizes the stator coils accordingly.
Types of BLDC Motor:
In the Out-Runner type, the magnets are placed on the outside of the stator, as shown in the fig. below.
Compared to the in-runner type bldc motor, the out-runner has more mechanical advantages.It has comparatively more torque.
Comparatively, It can swing heavier props.
In the In-Runner type of motor, the magnets are placed on the inside of the stator, as shown in the fig. below.
Comparatively, it runs on high RMP.
Advantages of a BLDC motor:
Better speed v/s torque characteristics
High dynamic response
Long operating life due to lack of electrical and frictional losses
Higher speed ranges
Applications of BLDC Motor:
Heating and ventilation
So now you know basic motor information – we created it in short form so anytime when you’ll forget something it’ll be easy for you to open our post and check it.
Our amazing technical department prepared a new post specially for you. Here you can get a simple explanation of complicated things: important terms, electric motor types, BLDC motor construction, and its working principle.