Special Machines (Permanent Magnet Synchronous Motor) Interview Questions

Special Machines (Permanent Magnet Synchronous Motor)  Interview Questions

[1] What is the PMSM?
In medium and small size synchronous motors, DC field can be produced by permanent magnets. Such kind of motors are called as PMSM

[2] What are the advantages and disadvantages of PMSM
Advantages

Elimination of field copper loss
Higher power density
Lower rotor inertia
Robust construction
Disadvantages

Power rating low
Motor power factor can not be controlled because of field excitation cannot be controlled

[3] What are the classification of PMSM
Based on construction
    Surface mounted PMSM
    Interior mounted PMSM
Based on the nature of voltage induced
    Sinusoidally excited
    Trapezoidally excited

[4] Give some applications of PMSM
Robots
Machine tools

[5] Define torque angle
The angle between excitation emf and supply voltage. This angle is called torque angle or load or power angle .

[6] What are the different classifications of synchronous motor?
(i) Wound field synchronous motor
      Cylindrical rotor construction
      Salient pole rotor construction
(ii) Permanent-Magnet Synchronous Motors
      Surface mounted (Projecting Type and Inset Type)
      Interior Buried Type
(iii) Synchronous Reluctance Motors
(iv) Hysteresis motors

[7] What are the different modes employed to achieve variable frequency control in synchronous motors?

Separate or true synchronous mode
Self controlled mode

[8] Why a Synchronous Motor without damper winding is used, in the drive system employing a Cycloconverter?
A Synchronous Motor without the damper winding is used, because the damper winding reduces the inductance of the machine, and therefore is ability to filter out harmonics in the output voltage of Cycloconverter. Since the drive operates in self-controlled mode, the damper winding is not needed for its converter.

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