With Europe planning to be a ‘Carbon Neutral Economy’ by 2040, the future of mobility is electric.
Out of the different electric vehicles that exist today, electric scooters provide the most promising solution. Besides being more ec0-friendly than other electric transportation alternatives, their portable nature and compact size make them ideal for the urban commute (and definitely a futuraride!).
Today, we’ll try to explain the working mechanism of this amazing ride.
An electric scooter, as the name implies, runs on electricity. It has a battery that stores electric power, which is then converted into kinetic energy by a motor. The main working part or the powerplant of an electric scooter is its motor.
Let’s try to understand how it works!
How Does an Electric Scooter Motor Work?
From acceleration and top speed to the climbing ability, it’s the motor of an electric scooter that determines almost all aspects of its performance.
Before we take a look at the working mechanism and types of electric scooter motors, let’s see what are the most important things that we may want from them.
Things You May Want From an Electric Scooter Motor
An electric scooter motor needs to have enough starting torque to move the scooter from a standstill.
It must have adequate power to take you wherever you want, be it an uphill place. It must also be controllable so as to vary the speed of your scooter as per your requirement.
Most importantly, it must be reliable and durable to last a long time.
Types of Electric Scooter Motor
There are two common types of motors that are used in electric scooters. They are:
- Brushed DC motors.
- Brushless DC motors.
Let’s see how each of them works and what advantages does one has over the other.
Brushed DC Motor
A brushed DC motor is a motor in which the electric current is supplied to the electromagnet coils on the rotor via a pair of brushes. The main feature of this motor is that the electricity is supplied to the part of the motor that rotates.
This type of motor was developed back in the early 19th century and is mainly popular due to its low cost and simple operation.
Here’s a diagram of a brushed DC motor, which can help you understand how this motor works.
Functional Parts of a Brushed DC Motor
A brushed DC motor comprises of the following parts:
The Brushes are made of a conductive material that is not abrasive. They are meant to conduct electricity from the source (the scooter battery) to the electromagnetic coil of the rotor. This makes it possible for the electromagnetic coils of the rotor to have a supply of electricity even when they are rotating with reference to the brushes.
The Commutator is generally made of copper or another highly conductive metal. It receives electricity from the brushes and conducts it to the electromagnet windings of the rotor. There are two commutator contacts for every coil in the motor.
The Armature, also called the rotor, is the part of the motor that rotates and converts the electric energy to kinetic energy (motion). It has a bunch of coils of wire wound on it which generates the magnetic field that rotates the motor’s shaft.
The Stator is the housing of the motor that has a permanent magnet in it. This magnet provides the magnetic field that interacts with the magnetic field of the rotor’s electromagnets to rotate the rotor. Some DC motors might have an electromagnet in the stator. In the case of such motors, the stator’s electromagnet draws electricity from the same source as the rotor’s coils.
The Shaft is the output part of the motor where the energy is used to do work, that is rotating the wheel of a scooter.
What Happens When You Turn a Brushed DC Motor on?
When you turn on a brushed DC motor, the following sequence of events happens:
- The electric current flows from the brushes into the commutator and then the windings of the electromagnet of the rotor.
- This induces a magnetic field in the rotor which interacts with the magnetic field of the permanent magnets of the stator assembly.
- The interaction of these magnetic fields makes the rotor rotate and convert the electric energy of the source into rotational energy.
One thing to note here is that the magnetic field of the rotor’s windings changes direction every 180 degrees of rotation. To keep the direction of rotation constant, the contact between the commutator and the brushes reverses the direction of flow of the current every 180 degrees.
In addition to that, the direction of the application of magnetic force to the rotor changes as it rotates. This means that the motor will have different speeds at different points of rotation. This is compensated by having multiple coils in the rotor so that the motor always has a uniform speed and torque output.
What Determines the Power Output of a Brushed DC Motor?
One of the most important characteristics of an electric scooter motor is its power output. As power in any electric system is the product of the voltage and current, it means that increasing either of these will make the motor more powerful.
To make a motor more powerful, the windings on the rotor can be increased so that more current passes through them. Increasing the input voltage also increases the power output of a DC motor. Moreover using more powerful magnets can also increase the power of the motor.
Pros and Cons of Brushed DC Motors
Brushed DC motors have certain advantages over brushless motors. These include:
- Low cost.
- Higher torque over a larger range of rotor speeds.
- Smooth motion at low speeds.
- Good speed control.
- Can be rebuilt.
- Works better in all kinds of environments.
- Does not need a controller when operating at a constant speed.
However, there are some limitations to brushed DC motors too. These include:
- Lower life due to the solid-to-solid contact between the commutator and the brushes.
- Higher operating noise.
- High rotor inertia.
- Electromagnetic interference caused by brush arcing.
Brushless DC Motors
Most of the electric scooters nowadays use a brushless DC motor instead. This is mainly because these motors can fit inside the hub of the wheel and don’t need to be mounted on the frame.
A brushless DC motor (BLDC), as the name implies, does not have brushes to conduct electricity. It has a totally different design and working principle as compared to a brushed motor. This type of motor was developed in the 1970s and is widely popular mainly because of its long life and less noise.
Here’s a diagram of the internal parts of a BLDC motor:
There are two main functional parts of a BLDC motor. They are:
- The rotor, which is a permanent magnet and is placed inside the stator.
- The stator, which has electromagnet coils on it.
Some BLDC motors might have fixed electromagnet coils in the middle and permanent magnets attached to the stator. In such motors, the stator is what rotates.
How Does a Brushless DC Motor Work?
The working principle of a BLDC motor is simple: you provide electric current to the stator coils and the resulting magnetic field rotates the rotor, which is a permanent magnet. As you can notice, the coils of the BLDC motor do not rotate, there is no need for brushes and a commutator in such a motor.
However, if the coils are fixed in place, how do you change the polarity of the electromagnet which is required to keep the rotation of the motor unidirectional? That is achieved by using a controller.
The controller either works with a rotor position sensor or with the help of magnets on the body of the motor. Here’s the difference between these two types of controllers:
- Sensor-Based BLDC Controllers: A sensor is attached to the rotor that determines its location at any given time. This location data is then sent to the controller. The controller sends current with specific polarity to specific coils to make sure that the magnetic field is always in a position to keep rotating the rotor the right way.
- Sensorless BLDC Controllers: In this approach, electromagnets are placed on the body of the motor. The rotation of the rotor induces an electric current in these electromagnet coils. The intensity and direction of this current tell the controller to excite specific coils on the stator to rotate the motor.
The need for a controller makes a BLDC motor inherently complicated as compared to a brushless one. However, BLDC motors have a number of advantages that make them feasible for many applications, especially for usage in electric scooters.
Factors Affecting the Power Output of a BLDC Motor
The power output of a BLDC motor depends on the following:
- The resistance and hence the current drawn by the coils of the stator.
- The strength of the permanent magnet used to make the rotor.
- The voltage supplied to the coils of the stator.
Pros and Cons of a BLDC Motor
BLDC motors, also used in ebikes, are better than their brushed counterparts because they:
- Are compact in size.
- Have higher starting torque.
- Offer better speed control.
- Are more efficient.
However, all of that comes at a price. There are some downsides to BLDC motors too, such as:
- They cost more than brushed motors.
- Wiring a brushless motor is complicated owing to the use of electronic controllers.
- These motors need a controller even for constant speed usage.
It brings us to the next question; what type of motor is better for an electric scooter?
Which Electric Scooter Motor is Suitable for You?
The answer to that depends on a lot of factors. The most important of them is cost. After that, there is the reliability and complexity factor. But in the end, it all comes down to your personal decision. As we said earlier, both motor types have their own pros and cons.
An electric scooter with a BLDC motor can be a better option for you, if:
- You want a scooter with low noise.
- You want to use the scooter very often and the age of the motor concerns you.
- Cost is not an issue with you, and you can afford to pay more.
- You want finer control of the speed of the motor.
- You want a motor with high low-end torque for negotiating slopes at low speeds.
On the other hand, you can go for an electric scooter with a brushed DC motor, if:
- You want a scooter at a lower price.
- The age of the motor is not an issue for you.
- You want simpler wiring and electronics in your scooter.
Our Verdict on Electric Scooter Motor
If you ask us, we’d say a brushless DC motor is always a better choice for any automobile application including electric scooters. It is because these motors do not need maintenance and run quieter. Moreover, they are more efficient and have finer control over speed and torque output.