Project co-funded by the Erasmus + Program of the European Union

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The "Manufacture a kart with alternative energies" project is co-financed by the Erasmus + program of

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Virtual mobility in Germany

German diary

Beluga landing.MP4
AirportToSchool.MP4
Quiz Bremen.pdf

Monday, 22.03.2021

On our first day we met at 10 a.m. via video conference on MS Teams. Due to technical problems in France our headmaster started at 10:30 with welcoming the participants from France, Italy, Malta and Spain.

Afterwards we did a short presentation of Bremen and our school pointing out following:

  • Bremen is the smallest of 16 federal states in Germany

  • The state Bremen consists of two cities: Bremen and Bremerhaven

  • The Airbus Beluga XL is transporting plane parts between France, Germany and Spain and regularly lands in Bremen (video)

  • The airport is surrounded by aviation and aerospace industry

  • You can take the tram from the airport to our school (about 20 minutes ride) (video)

  • Our school is located in the centre of Bremen and has over 100 teachers and technical instructors and over 2500 students from countries all over the world (picture)

  • The courses our school offers

  • Informations about the dual apprenticship as a car mechanic

  • Our teaching materials

  • Informations and pictures of the city centre, sights and cultural events

  • Nature and parks in Bremen

  • The city of Bremerhaven and its sights (Maritime museum, climate house)

  • Science in Bremen (Universum science center, drop tower)

  • Having fun in Bremen: Werder Bremen and Beck's brewery

We created four group rooms in Teams for international student teams (at least one student of each country), which were named after the Bremen Town Musicians: donkey, dog, cat and rooster.

Today the groups had to solve a quiz about Bremen to find the solution words: "Welcome Valdepeñas, Alès, Malta, Gallarate!

As the students couldn't finish the quiz until 12 p.m. they could try to solve it until tuesday.

Quiz Bremen_answers.pdf

Tuesday, 23.03.2021

On the second day we took a look at the components of a battery electric vehicle (BEV) in general and the components used in our Kart.

Before working on a BEV you have to deal with the safety. The ECE (Economic Commission for Europe) regulation 100 states that high voltage are electric components or circuits working with a voltage between 60 V and 1500 V DC or between 30 V and 1000 V AC rms. As we use a voltage of 48 V DC we have less safety rules but still have to be cautious.

As the Kart is rather simply equipped, we don't need parts like an electric steering, brake (with an electrical vacuum pump), air condition and heater. Also a reduction gear and a DC converter are not needed. So the components we really need in our Kart are:

  • electric motor

  • battery with battery management system (BMS)

  • controller (inverter, HV control unit) with emergency shut-off

  • accelerator and switches

  • display

After a video presentation of the safety rules and the components of a BEV as well as our Kart the students had to solve the following quizzes:

At the end of the day we showed our workshop and the progress of our Kart. The motor, controller and operating units are installed. Right now we are planning our battery with the battery management system.

Wednesday, 24.03.2021

Today we took a look at electric motors, their principles and the types used in BEVs.

The main principle of an electric motor is magnetism and the fact that magnets with similar poles push each other while magnets with opposite poles attract each other. Electromagnetism is used to change electric fields when needed (commutation).

Electric motors use two different types of current:

  • direct current (DC)

  • alternating current (AC)

Direct current (DC) motors in vehicles are often used as starter motors. But BEVs mainly use alternating current (AC) motors, which can be divided into:

  • synchronous motor

  • asynchronous motor

While a DC motor just has a plus (+) and a minus (-) connection, the AC motor is powered with three phases (U, V, W) of AC voltage shifted by 120 ° each.

Our Kart uses a brushless direct current (BLDC) motor with three phases (U, V, W) instead of just + and - . When looking at the controller on friday we want to find out what's so special about the brushless DC motor.

Before the students took a quiz on electric motors, the Italian colleagues showed us a video of their running Kart and explained some details of their special air pressure powered motor.

Thursday, 25.03.2021

To power the electric motor of a BEV, a powerful traction battery is needed. We dealt with the requirements and characteristics of a traction battery in general and Li-Ion batteries. Then we looked at parallel and series connection of battery cells, the charging and discharging and why a battery management system (BMS) is needed.

We checked the battery requirements for our Kart and why the whole battery capacity is based upon the weakest cell.

After the presentation the students got the task to search the internet for battery cells and find out how to combine them (parallel or in series) to achieve the requirements (of a fictional customer) and to give a cost estimate. They should post their solutions on a Twinboard in the Twinspace on eTwinning.

The French school showed us a very interesting video where they introduced their Kart with its components. They also explained the setup of their Li-Ion battery pack with its BMS, the circuits and the housing.

Friday, 26.03.2021

On our last day we started with a video of Bremen (driving through the city on an e-scooter and walking through the city centre) as our guests sadly could not visit us personally. We watched it a few minutes until all our guests had entered the video conference.

Our last topic this week were the power electronics components of a BEV like the boost and buck converter and the inverter. And we checked the BLDC motor design, its function and its controller signal.

Essential for the power electronics are insulated-gate bipolar transistors (IGBT) and pulse width modulation (PWM) signals.

Boost and buck converters are simple circuits with a high efficiency. Their IGBTs are controlled with PWM signals and they are used to step up or step down voltages.

The inverter turns the battery DC voltage into the motor AC voltage. It also consists of a simple circuit and is using four switches to turn the current direction in the load. The sinusodial voltage is achieved by the charging and discharging characteristics of a coil.

Finally we found out that the BLDC motor acts like a synchronous AC motor, which is controlled by a clocked square-wave three-phase current. The controller measures the rotor position and changes the magnetic fields in the stator coils with one phase always currentless, one phase connected to B+ and the last one connected to B-. The BLDC controller signal looks like an edgy sinusodial signal.

It's been an interesting week with some technical problems, some delays and organisational problems. We would have loved to meet our guests in person and show them around in our beautiful city.

But as we had to do a virtual mobility we decided to focus on the technical part. We gained great impressions of the other Karts and the progress of our partner schools. We are looking forward to the Italian mobility and hope to catch up with the other partners.