What Type of Electric Motor is Used in Hybrid Cars

Electric motors are of course different from gas motors.  There are different types depending on the manufacturer and cost.  There are three distinct types.

What type of electric motor is used in Hybrid Cars?: There are three types of motors that can be found in a hybrid car.  A hybrid could have one of the following motor systems: 

  1. Induction motor that has three phases
  2. Multiphase induction motor that has more than three phases
  3. The electric motor that has a permanent battery

What is a Three Phase Induction Motor for a Hybrid Motor?

The three-phase induction motor is based on technology designed by Nikola Tesla in 1883.  He designed a motor that a polyphase induction motor.

First of all, I will explain the term: induction motor.  An induction motor has two main parts that consist of a stator and a rotor. The stator holds the rotor and it is stationary.  The rotor is able to spin within the stator.

The stator has 3 coil windings.  These windings are within the slots of the stator.

When a current passes through the wiring in the stator, a rotating magnetic field is created.  The current comes from the electric motor battery pack in a hybrid vehicle.

The RMF or rotating magnetic field causes the rotor to spin. It is easy to see why this type of motor is powerful, it is almost completely self-starting.  It just needs alternating current to begin to spin the rotor.  Nevertheless, the rotor will never spin faster than the speed of the rotating magnetic force.  The difference between these two speeds is called slip.

I thought that it would be a good idea to try to visualize what is happening within a 3 phase induction motor. Imagine that you have a plastic glass.  Drop another plastic glass into the first plastic glass. Add some water between the two of them, just enough so that the second glass is not touching the inside of the first glass.  Now with a small instrument, stir the water that is lodged between the two glasses.

The second smaller glass will begin to spin. The water that is spinning is acting in a similar fashion to the current in a stator.  It is causing the glass to spin.

What is a Multi-Phase Induction Motor for a Hybrid?

This type of induction motor is not presently mainstream.  Nevertheless, there are a lot of press articles that feel that it is going to revolutionize the hybrid car industry.

Chorusmotors, a company that has its headquarters based in Gibrator has designed a multi-phase induction motor that has advantages over the 3 phase induction motor.

This motor is the one that is being used since around 2010 by Delta airlines for taxiing their 737NGs.  This system is called Wheeltug. A Wheeltug has a powerful multi-phase induction motor.  The Wheeltug is mounted into the nose wheel of an aircraft. It is powerful enough to pull the plane into its gate without the need of a tow tug.  This saves a lot of time and money for an airline that has to deal with many variables that can cause delays.

Having a lot of torque is important for pulling large airplanes.  Torque is the force that is turning or twisting an axis.  If this type of motor was designed into a hybrid car, it will provide a lot of power to begin acceleration.  This fast acceleration will increase the amount of kinetic energy generated that can be converted into current for charging the batteries for the electric motor as the vehicle slows down.

I have not been able to determine if the Chorusmotors multi-phase induction motor is being used in a hybrid.  Nevertheless, I thought that I should mention it because it will mostly happen at some point in the future.

One study by Researchgate.net states this motor would be highly advantageous for electric motors that could be used in electric cars and hybrid cars.   The following factors make it a great option:

  1. Enhanced fault tolerance, which means that if a phase malfunctions,  the unit may still be able to continue to function.
  2. This motor is very efficient.  It does not require a lot of energy compared to the three-phase model.
  3. Very low acoustic noise.  Acoustic noise can be very high in many motor systems.
  4.  I thought perhaps, that the added phases would cause more vibration, but it has been proven that the multi-phase type creates less vibration. Vibration in a hybrid can cause more wear and tear to the vehicle in general.

Another aspect that I found interesting about this type of motor is that it does not heat up as fast at the three-phase motor that can be found in many different hybrid models.  Apparently, it can be adequately cooled by having good air circulation, but this requires a much more complex transmission.

How Does an Electric Motor with a Permanent Magnet Work for a Hybrid?

I surprised to find out that my vehicle is a permanent magnet/synchronous AC electric motor. In other words, I probably have one of the newer types of electric motors. I was pleased to find out that it works efficiently due to its magnet system.

The permanent magnet will allow the rotor to spin at the same speed of the stator.  This allows the electric motor to generate more energy.

These can be mounted in two different ways.  One way is to surface mount them.  The second method is to embed them within the laminations in the stator.

The magnets themselves consist of rare-earth metals.  Rare-earth metals are usually mined close together, but locating them is not an easy task.  There are spread out all over the planet.

Rare-earth metals are not only used for electric motors, but they are found in many other products such as rechargeable batteries and fluorescent lighting.

How does a permanent magnet increase the rotor speed?

With a normal induction motor, the rotor will never match the speed of the electromagnetic current that is within the stator when the electric motor’s battery pack is supplying power.  The difference in speed is called slip.  In other words, slip is the difference between the speed of the rotor and the rotating magnetic field within the stator. 

With an electric motor that has a permanent magnetic field, the rotor is able to stay in sync with the rotating magnetic field within the stator.  This creates more torque and power.  The reason that the rotor is able to match this rotating field is because of the added pull of the permanent magnet. This magnet is not present in the average induction motor. The stator has to rely solely on the current supplied from the batteries that are connected to the electric motor assembly.

photo- comsol blog

Are Electric Motors in Hybrid Cars Hard to Maintain?

Perhaps you are wondering if it is worth it to buy a hybrid car because you have heard rumors that they are hard to maintain.  Before buying a hybrid that plugs in, I thought that the maintenance tactics used would be very foreign to me which could increase my stress level.  I know how to maintenance a non-electric motor, but what was going to be in store for me with this new technology?

Since a hybrid has both a gas and an electric motor, you will need to treat the gas portion in the same matter as you would a normal car.  You need to :

  1. Change the oil in the gas motor, although I was too by my mechanic that I could travel double the distance versus the typical gas car. The other option is to change the oil once every 6 months (typical cars that period is every 3 months).
  2. Fluids, filters, and spark plugs have to be maintained in the gas motor. Again, there is a lot less wear and tear involved with a hybrid, such maintenance is minimal.

With respect to the battery pack for the hybrid vehicle, they are usually guaranteed for the average life of the battery or a set number of miles.  If you are usually your hybrid in a normal fashion, you may have to have the battery replaced after 10-11 years.  Nevertheless, if you using your hybrid as a taxi or uber vehicle, you are going to reach the maximum mileage rather quickly.

Another aspect of the battery pack for a hybrid is that it can become unbalanced.  A battery pack could have as many as 28 or more individual cells.  If one or more of the cells become weaker faster than the others, your battery pack will be unbalanced.  It is best to follow the suggestions in your manual for the times for maintenance, especially with respect to the battery cells.

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