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In the design of single-phase induction motor. The flux density in stator theeth is ____________ for For high torque machine and ____________ for general purpose machine.
8 Wb/m² & 1.4 to 1.7 Wb/m²
7 Wb/m² & 1.1 to 1.7 Wb/m²
1 Wb/m² & 1.4 to 1.7 Wb/m²
8 Wb/m² & 1.1 Wb/m²
8 Wb/m² & 1.4 to 1.7 Wb/m²
The flux density in stator teeth of a single-phase induction motor is a critical design parameter that directly impacts the saturation level of the magnetic circuit. For high-torque machines, a higher flux density (typically 1.8Wb/m2 or approximately 1.8 T) is permitted to maximize electromagnetic torque production, whereas general-purpose motors utilize a more conservative range of 1.4 to 1.7Wb/m2 to minimize losses and heat.
The flux density in stator teeth of a single-phase induction motor is a critical design parameter that directly impacts the saturation level of the magnetic circuit. For high-torque machines, a higher flux density (typically 1.8Wb/m2 or approximately 1.8 T) is permitted to maximize electromagnetic torque production, whereas general-purpose motors utilize a more conservative range of 1.4 to 1.7Wb/m2 to minimize losses and heat.
Bt=AtΦ — Relation between flux, area, and density
Ph=KhfBmax1.6V — Hysteresis loss dependency on flux density
Flux density in the teeth is governed by the relation Bt=AtΦ, where Φ is the flux per pole and At is the cross-sectional area of the teeth. High-torque applications require high magnetic loading, pushing teeth flux density towards the saturation knee of the B-H curve. Conversely, general-purpose machines prioritize efficiency and lower iron losses, requiring lower flux density values to avoid excessive magnetizing current.
High-torque designs operate closer to saturation to increase air-gap flux.
General-purpose motors balance iron losses with size and cost.
Flux density units are Webers per square meter (Wb/m2) or Tesla (T).
Increased flux density leads to higher hysteresis and eddy current losses.
Higher flux density leads to smaller motor frame size for a given rating.
Optimized teeth design improves torque-to-weight ratio.
High flux density increases iron losses and reduces overall efficiency.
Higher magnetizing current requirements for saturated machines.
Industrial high-starting torque motors (High flux density)
Domestic fans and centrifugal pumps (General purpose)
| Feature | High Torque | General Purpose |
|---|---|---|
Application Type | 1.8 Wb/m2 | 1.4 to 1.7 Wb/m2 |
Note: The provided question option '8 Wb/m²' is a common typographical error in legacy textbooks where it typically implies 1.8 T.
The range 1.4 to 1.7T is standard for most industrial induction motor designs to ensure a balanced operating point.
A is correct — High torque machines require higher flux densities to maximize electromagnetic torque, while general-purpose machines operate at lower, more efficient levels.
Remember that flux density in electrical machines is inversely proportional to cross-sectional area; reducing teeth area significantly increases flux density, which may lead to magnetic saturation and excessive iron losses.