Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
Mostly, synchronous motors are of
alternator type machines
induction type machines
salient pole type machines
smooth cylinderical type machines
salient pole type machines
Synchronous motors designed for low and medium speeds are predominantly of the salient pole type. These motors feature a rotor with projecting poles, which is structurally optimized for the multi-pole configurations required to maintain a synchronous speed NsтАЛ=P120fтАЛ at lower frequencies.
Synchronous motors designed for low and medium speeds are predominantly of the salient pole type. These motors feature a rotor with projecting poles, which is structurally optimized for the multi-pole configurations required to maintain a synchronous speed NsтАЛ=P120fтАЛ at lower frequencies.
NsтАЛ=P120fтАЛ тАФ relationship between synchronous speed, frequency, and number of poles
The salient pole rotor consists of individual pole pieces bolted onto a spider, creating a non-uniform air gap. This geometry is ideal for low-speed operation where a high number of poles (P) is necessary. In contrast, smooth cylindrical rotors are utilized in high-speed applications like turbo-alternators to minimize centrifugal stresses and windage losses.
Salient pole machines have a large diameter and short axial length.
The projecting pole construction provides robust support for field windings.
High number of poles leads to lower speed requirements for the same frequency.
Cylindrical rotors are preferred for 2-pole or 4-pole high-speed turbo-generators.
Better cooling due to projecting poles
Suitable for high-pole count, low-speed operation
Economical construction for medium to large power ratings
Higher windage loss at very high speeds
Not suitable for high-speed turbo-alternators due to centrifugal force limitations
Hydro-electric power plants
Industrial low-speed synchronous motors
Synchronous condensers
| Feature | Low Speed | High Speed |
|---|---|---|
Construction | Salient Pole | Cylindrical |
Salient pole rotors are characterized by a non-uniform air gap, which results in saliency and non-zero reluctance variation.
Option D (cylindrical) is incorrect because it describes high-speed rotors, typically used in thermal power plants.
C is correct тАФ Mostly, synchronous motors, especially those used in industrial applications, are of the salient pole type to accommodate a higher number of poles.
Always remember: salient poles = low speed, many poles; cylindrical = high speed, few poles (2 or 4).