1. OBJECTIVE
In this experiment, you will observe the engine and generator parameters when using direct starting. It will analyze the relationship between speed and frequency in a synchronous generator and, finally, it will observe the relationship between the output voltage and the excitation current in the rotor.


At the end of this experiment, you should be able to:

understand how the command and power circuit of a contactor works, understanding the possible applications of this type of equipment in electrical installations;

observe the peak current caused by direct starting of the motor, understanding that this type of starting causes an abrupt variation in current and torque at the moment of activation;

build a graph where the increasing linear behavior of the rotor shaft speed with the frequency of the generator voltage can be observed;

be able to find the number of generator poles without having to analyze its board or internal construction;

understand that the voltage supplied by the generator can be found by multiplying the excitation current, frequency and a constant;

realize that there is a region of low frequencies where there is no generator output voltage and consequently no excitation current.

2. WHERE TO USE THESE CONCEPTS?
Rotary machines are essential for the modern world. They are responsible for converting electrical energy into mechanical energy in electric motors and mechanical energy into electrical energy in electrical generators. In Brazil, approximately 40.7% of the electrical energy generated is destined for various industrial sectors, with almost half of this energy being used for engines.


3. THE EXPERIMENT
This experiment will use the components of the teaching bench of rotating electrical machines to perform the direct start, verify the relationship between speed and frequency and the relationship between voltage and excitation current. To do this, it will be necessary to use contactors, in order to configure the different connections, in addition to a three-phase induction motor and a three-phase synchronous generator, so that it is possible to establish the studied connections.


4. SECURITY
The use of personal protective equipment (PPE) in engineering course laboratories varies from environment to environment, according to the characteristics and risks inherent to each activity, taking into account the materials and equipment used. In this practice, it is recommended to wear closed shoes and hair tied up.


5. SCENARIO
All the materials necessary for this practice, including the motor and generator module, in addition to the safety cables for circuit connections, are available on the rotating electrical machines teaching bench.