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Industrial Brushless Servomotors Episode 2

Tham khảo tài liệu 'industrial brushless servomotors episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Brushed DC motors 15 the motor during acceleration and deceleration may be ignored in comparison to the amount supplied over the complete cycle. Chapter 5 covers the rating of the brushless motor in more detail and includes cases where the duty cycle demands a relatively high input of energy during periods of speed change. Power losses Figure 1.11 shows how the electrical power input is distributed as the DC motor performs its normal task of converting electrical energy into mechanical energy. The output power is lower than the input power by the amount of the losses which appear mainly in the form of heat within the motor. Figure 1.11 Power distribution in the DC motor 16 Industrial Brushless Servomoters 1.4 The i2R winding loss The flow of current I through the rotor winding resistance R results in a power loss of PR. Note the dependence of this loss on the motor torque Kyi. Friction windage and iron losses As well as friction and windage there are other effects of the physical rotation of the rotor. For example as the rotor position changes with respect to the permanent magnetic field flux reversals take place inside the iron core which encourage the flow of eddy currents. The consequent losses and rotor heating increase with rotor speed. Torque loss and power loss at constant speed The iron friction and windage losses result in a reduction in the available output torque. The loss at constant speed is Tioss Tf Dw where Tỉ is the torque due to constant friction forces such as those produced at the rotor bearings and D is a constant of proportionality for speed-dependent torque losses due to viscous effects such as iron losses. The constant D is known as the damping constant expressed as Nm rad s-1. The product of the torque loss and the motor speed is known as the speedsensitiveloss. Adding the i2R loss gives the total power loss in SI units as Floss DlS p R P1OSS is the difference between the electrical power at the motor input and the mechanical power at the .