I. Introduction
The motor is a very important part of your electric scooter and knowing a bit about the motor may help you in taking good care of it.
The topics discussed in this article are what a DC electric motor is and how does it work, types of electric motors used in electric scooters and their pros and cons, and frequently asked questions.
II. What is a DC Electric Motor and how does it work?
A DC (Direct Current) motor is an electrical unit where the input electrical energy is converted into mechanical energy. The DC motor works on the principle ‘when you place a current-carrying conductor in a magnetic field, the conductor undergoes a mechanical force’ and the magnitude of this mechanical force can be calculated.
In a normal DC motor, the rotor is positioned inside the motor and the stator is on the outside. As the name indicates, the rotor rotates and the stator will be stationary. The rotor will have coil windings where the direct current flows through these windings and the stator may be made of either permanent magnets or electromagnetic windings.
When you allow the direct current to pass through the rotor windings, the magnetic field created within the stator starts attracting and repelling the electromagnetic windings on the rotor. This process makes the rotor starts rotating.
The circuit system has a commutator, to keep the rotor continuously rotating. When the rotor comes in perfect alignment with the magnetic field, it will stop its rotation. However, the commutator at that instant will reverse the current flow into the rotor and reverse the magnetic field. This action of the commutator ensures the continuous rotation of the rotor.
Different parts of a DC motor:
Armature or Rotor – The armature consists of magnetic laminations insulated from one another and rotates on its axis. The magnetic laminations on the armature are separated from the field coil (stator) by a small gap containing air.
Stator or field coil – This is a stationary part and has windings for producing a magnetic field.
Commutator and Brushes – The commutator is made of copper and it supplies the direct current to the armature winding or the rotor.
The commutator brushes are made of carbon and graphite. The brushes work as a conduit to pass the direct current from the source to the rotating commutator.
The DC motor is the source of power that runs your electric scooter, whether it is the maximum speed or the ability to climb a steep hill, it plays an important role and of course, it needs the support of a good battery.
The DC motors are differentiated by their power in watts. A DC motor with a higher wattage will consume more battery power and in turn produces more mechanical power and gives you higher maximum speed, faster acceleration, increased rider weight, and ability to climb a steep hill with ease.
Many times two DC motors of the same watts rating consuming the same electrical power may not give the same mechanical output and it can be due to the difference in the quality of construction of the motors and also their individual efficiency.
Normally, electric scooter manufacturers mention the watts of the motor fitted in the scooter, however, the same can be calculated when you know the voltage and current used by the motor. Assume that the DC motor of your electric scooter is running with 36 volts and 15 amps, then the motor power is 36×15=540 watts.
A DC motor has two ratings, peak power, and continuous power. Peak power implies the maximum amount of power the motor can consume for a very short period and the peak power can be 2 to 5 times the continuous power. Continuous power refers to the actual power of the motor. Many electric scooter manufacturers may mention peak power to influence the customers but that rating is not of much relevance.
III. Types of electric motors used in Electric Scooters and their Pros and Cons
There are different types of DC motors, however, let us concentrate on the two types of DC motors used in electric scooters such as the brushed DC motors and brushless DC motors (popularly called BLDC motors).
Brushed DC motors
The construction of a brushed DC motor has all the standard features of an electric motor. A Brushed DC motor follows the old technology and uses the standard commutator and brushes system that takes care of reversing the current at every half cycle and ensures the continuous rotation of the rotor.
Brushed DC motors are still popular in many fields, including some electric scooters. However, they are gradually replaced by the more compact and efficient BLDC motors.
A brushed motor used on an electric scooter needs to be mounted near the rear wheel and the drive is transmitted to the rear wheel through a drive arrangement (chain, belt, or gear drive).
- Low initial cost compared to BLDC motor.
- High reliability.
- The controller is simple and not expensive
- Wiring is simple.
- Has an efficiency of 75 to 80%.
- Worn-out carbon brushes can lead to fire hazards.
- The carbon brushes need frequent replacement.
Brushless DC (BLDC) motors
A brushless DC motor, unlike a brushed DC motor, does not have a commutator or commutator brushes. An electronic servomechanism system replaces the function of the commutator in the brushless DC motor. Brushless DC motors are popularly called BLDC motors or electronically commutated (EC) motors. Most quality and reputed electric scooters use BLDC motors.
Two types of BLDC motors:
Out-runner type BLDC motor
In this type of BLDC motor, the rotor of the motor is outside and the stator is inside. This means the position of the stator and rotors are reversed. Out-runner BLDC motor is popularly called hub motor since your electric scooter wheel is directly assembled and connected to the rotor of the hub motor.
The rotor of a hub motor is made of permanent magnets and the stator has a coil arrangement. BLDC hub motor uses an electronic controller to energize the coils of the stator to keep the rotor rotating continuously, and a sensor (like Hall Effect) senses the position of the rotor and helps the controller energizes the coil correctly.
Hub motor does not require any other drive system (chain, belt, or gear drive). Hub motors are widely and popularly used in electric scooters, on the rear wheel or on both the wheels (dual hub).
The hub motors are compact and simple, however, taking out the motor for servicing or replacement is a bit complicated.
Overloading the BLDC motor beyond a limit affects the life of permanent magnets due to a temperature rise.
In-runner type BLDC motor
In-runner BLDC motor has the features of a standard DC motor, has its rotor inside and the stator outside. The rotor is made of permanent magnets and the stator has a coil arrangement. In-runner BLDC motor needs to be mounted near the rear wheel and the drive is transmitted to the rear wheel through a drive.
In-runner BLDC motors has less weight compared to hub motors.
- BLDC motors have the advantage of long life, quietness, ease of maintenance, and low noise since they do not have commutator/brushes.
- BLDC motors can operate at high speeds and have high startup torque.
- BLDC motors are more efficient (85 -90%) and have better power-to-weight ratios.
- BLDC motors are less likely to overheat.
- The performance of the BLDC motor is better than brushed DC motors.
- The overall maintenance is less since there are no commutator/brushes.
- High initial cost.
- Complicated circuit and electronic controllers are required.
- BLDC motors use expensive permanent magnets and are costlier compared to brushed motors.
IV. Frequently asked questions
| 1 | Why a DC motor is used in the electric scooter? |
| The electrical energy used by an electric scooter is the energy stored in the batteries and batteries store electrical energy in the form of direct current (DC). Hence, DC motors are compatible with electric scooters. | |
| 2 | My electric scooter does not run, is the motor is faulty? |
| The motor is the most reliable part of your electric scooter, and it will not become faulty unless it is exposed to dust and water seriously. Check the battery and other controls. In all probability, they may be the cause of the motor not running. | |
| 3 | Can I improve the performance of the motor in my electric scooter? |
| Please study your owner’s manual. Some manufacturers may allow you to increase the power output of the motor marginally using the controller. It will improve the performance of your scooter, but, at the cost of the range and battery life. | |
| 4 | My owner’s manual does not mention the motor power (watts), can I calculate it? |
| Yes, you can calculate it, since you know the voltage and current used by the motor. Assume that the DC motor of your electric scooter is running with 36 volts and 15 amps, then the motor power is 36×15=540 watts. | |
| 5 | What is peak power? |
| The DC motor of your electric scooter can have two power ratings, peak power, and continuous power. Peak power implies the maximum amount of power the motor can consume for a very short period and the peak power can be 2 to 5 times the continuous power. Continuous power is the actual power of the motor. Many electric scooter manufacturers may mention peak power to influence the customers, however that rating is not of much relevance. |
V. Conclusion
An electric motor is like the heart of your electric scooter. Keep the motor in good condition, take care of it, and it will never fail your rides.
