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The rotational thrust generation (also called tangential force effect) is influenced by several geometric and electromagnetic parameters. An optimized design of these factors can improve the torque generation and thus the performance of electrical machines.
1. Geometric factors
a) Number of pole pairs p and pole pitch
• A higher number of pole pairs reduces the synchronous speed, but increases the torque density.
• The pole pitch \tau_p = \frac{\pi D}{p} (with D as the rotor or stator diameter) influences the distribution of the magnetic flux. An optimal pole pitch maximizes the magnetic coupling.
b) Air gap height
• A small air gap ( \delta ) improves the magnetic coupling between the rotor and stator because the magnetic resistance is reduced.
• However, an air gap that is too small can make manufacturing tolerances critical and lead to higher mechanical losses.
c) Stator and rotor tooth shape
• Wider teeth concentrate the magnetic field better, which increases the tangential force (rotational thrust).
• An optimized tooth shape with rounded edges reduces local saturation effects and improves flux guidance.
d) Winding arrangement
• Distributed windings lead to better magnetic flux distribution and higher effective torque.
• Concentric windings generate higher harmonics, which can have a negative effect on torque generation.
2. Electromagnetic properties
a) Magnetic flux density BÂ
• A higher flux density in the air gap fields leads to a stronger torque.
• Materials with a high saturation flux density (e.g. grain-oriented electrical steel) enable a higher magnetization.
b) Permeability of the iron cores
• A high permeability reduces the magnetic resistance and improves the coupling between the rotor and stator.
• High-quality electrical steel with low hysteresis improves the magnetic conductivity and reduces losses.
c) Permanent magnets (in synchronous machines)
• High-quality rare earth magnets (e.g. neodymium) enable stronger magnetic fields and higher torques.
• The arrangement of the magnets (e.g. surface-mounted vs. embedded) influences the reluctance torque and the field strength.
d) Current coating and winding inductance
• A high current density in the windings generates stronger magnetic fields and increases the rotational thrust-forming component.
• The leakage inductance should be minimized in order to use as much magnetic energy as possible to generate torque.
Summary: Which factors have a positive effect?
1. Geometric:
✅ Small air gap height
✅ Optimized pole pitch and tooth shape
✅ Distributed windings for uniform magnetization
2. Electromagnetic:
✅ High flux density B through optimized materials
✅ Highly permeable iron cores to reduce magnetic resistance
✅ Strong permanent magnets or field winding for high magnetization
✅ Low leakage inductance to maximize the usable flux
By combining these factors, the rotary thrust-forming component can be maximized, increasing the torque and efficiency of the machine.
Happy Amps Christian
The rotational thrust generation (also called tangential force effect) is influenced by several geometric and electromagnetic parameters. An optimized design of these factors can improve the torque generation and thus the performance of electrical machines.
1. Geometric factors
a) Number of pole pairs p and pole pitch
• A higher number of pole pairs reduces the synchronous speed, but increases the torque density.
• The pole pitch \tau_p = \frac{\pi D}{p} (with D as the rotor or stator diameter) influences the distribution of the magnetic flux. An optimal pole pitch maximizes the magnetic coupling.
b) Air gap height
• A small air gap ( \delta ) improves the magnetic coupling between the rotor and stator because the magnetic resistance is reduced.
• However, an air gap that is too small can make manufacturing tolerances critical and lead to higher mechanical losses.
c) Stator and rotor tooth shape
• Wider teeth concentrate the magnetic field better, which increases the tangential force (rotational thrust).
• An optimized tooth shape with rounded edges reduces local saturation effects and improves flux guidance.
d) Winding arrangement
• Distributed windings lead to better magnetic flux distribution and higher effective torque.
• Concentric windings generate higher harmonics, which can have a negative effect on torque generation.
2. Electromagnetic properties
a) Magnetic flux density BÂ
• A higher flux density in the air gap fields leads to a stronger torque.
• Materials with a high saturation flux density (e.g. grain-oriented electrical steel) enable a higher magnetization.
b) Permeability of the iron cores
• A high permeability reduces the magnetic resistance and improves the coupling between the rotor and stator.
• High-quality electrical steel with low hysteresis improves the magnetic conductivity and reduces losses.
c) Permanent magnets (in synchronous machines)
• High-quality rare earth magnets (e.g. neodymium) enable stronger magnetic fields and higher torques.
• The arrangement of the magnets (e.g. surface-mounted vs. embedded) influences the reluctance torque and the field strength.
d) Current coating and winding inductance
• A high current density in the windings generates stronger magnetic fields and increases the rotational thrust-forming component.
• The leakage inductance should be minimized in order to use as much magnetic energy as possible to generate torque.
Summary: Which factors have a positive effect?
1. Geometric:
✅ Small air gap height
✅ Optimized pole pitch and tooth shape
✅ Distributed windings for uniform magnetization
2. Electromagnetic:
✅ High flux density B through optimized materials
✅ Highly permeable iron cores to reduce magnetic resistance
✅ Strong permanent magnets or field winding for high magnetization
✅ Low leakage inductance to maximize the usable flux
By combining these factors, the rotary thrust-forming component can be maximized, increasing the torque and efficiency of the machine.
Happy Amps Christian
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