Differences Between Machine And Induction Machine
In this part, a survey of existing work and literature relating to the project is covered. The differences between PM machine and conventional AC machines
Induction machine is also called “asynchronies machine”. The rotor is placed in a rotating magnetic field and thus a rotating force can be attained.
The rotor is a rotating conductor and is mainly produced in cage shape. The stator generates the rotating magnetic field. The rotating of the magnetic field is not achieved by mechanical principle rather by applying AC current to the stator. The AC current applied to the electro-magnetic results in the rapid changing of the polarity of the magnetic field and make it equal to a rotating magnetic field. Brush conmmutator is …show more content…
Cost Moderate initial cost followed by a higher operating cost and maintenance. High purchasing price;
Lower operating cost and good energy saving which cut down operating cost.
Table 2 summary of comparison between PM and induction machines losses in electric machines
To investigate the efficiency of the machine, an essential part is to evaluate the losses in the motor. Losses in the machine is determined by the structure and working condition. Losses in the machines can generally be divided into two groups: electrical losses and mechanical losses. Electrical loss indicates the losses generated by the electrical interacting and circuit heat generating in the machine, generally includes copper loss and iron loss (also known as core loss). Mechanical loss is mainly generated by the friction in the machine structure.
The overall losses can be attained the simple relationship between input and output power: P_loss = P_in -〖 P〗_out=P_copper+P_add+P_core+P_mech (10)
Where the P_in and P_out are the input power and the output power of the machine. P_loss is the total loss. P_core, P_add and P_mech represent core losses, addtional losses and friction losses …show more content…
Here the induction machine is taken as example. The induction machine equivalent circuit is as shown below: Figure 11 Induction machine equivalent circuit
As shown in Figure 11, the parameters required are: stator resistance R_s, stator referred rotor resistance〖 R〗_r ', stator leakage reactance X_ls and stator referred rotor leakage reactance X_lr^ ', magnetizing resistance R_m and magnetizing reactance X_m.
To acquire the parameters 3 different tests are set: no power test, no load test and blocked-rotor test.
3.3.2 No power test
As described in the name, this test is applied to the motor with no power source. The purpose of no power test is to acquire the coil resistance of within the permanent magnet motors. To produce this test, firstly disconnect the power line cable from the machine, and connect the multimeter to the supply cable of any two phases of the AC motor(only 1 phase for the DC generator). Use the multimeter as the power supply and use the resistance measuring mode. Read the and record the result from the multimeter. Since only two phases are connected, the measured resistance value is a line-to-line value. Repeat this process for 3 times to acquire the value for 3 phases. Ideally, the resistance value in 3 phases are balanced, the 3 phase value would only vary in a minimal range. Work out the mean