Permanent vs. Field Winding

In summary: What about brushless DC motors? Do they use field excitation to vary the magnetic field strength?In summary, brushless DC motors use field excitation to vary the magnetic field strength. This allows them to operate at higher speeds than a standard DC motor.
  • #1
Phrak
4,267
6
This is a question about brushless DC motors. (I should have put that in the title)

How do you compare the two for an single geared vehicle drive system to get the widest power band in the same package size?

I've been looking over the max flux density of soft iron vs. neodymium permanent magnets. The field strength of high grade neodymium is quoted at a B_r of 14K Gauss, and B_R of soft iron at about 18K Gauss. But for the soft iron, the required copper reduces the effective pole crosssection.

(Can B_r and B_R be directly compared?)

Variable field winding strength can nearly double the operating speed range by decreasing the field stength at higher RPM, or so I've read. Where do I start?
 
Last edited:
Engineering news on Phys.org
  • #2
Don't compare the two. Neodymium iron boron permanent magnets give you large fields for free. No amp-turns required. All large PM motors have the PM in the rotor, and the coils in the stator, and a Hall-effect sensor to determine the armature position. The stator polarity and current (and motor torque) is controlled by solid state switches. Usually the motor's max torque is at zero RPM.
 
  • #3
What's the cost in field current?

Field windings could nearly double the low-end power. This may be the strategy used on diesel electric locomotives. Don't know.
 
Last edited:
  • #4
Phrak said:
What's the cost in field current?

Field windings could nearly double the low-end power. This may be the strategy used on diesel electric locomotives. Don't know.

:smile: Hi, field excitation is used when u require to vary the magnetic field strength in applications such as 'synchronous condensers' for PF improvement. Varible excitation is used in large alternators to adjust MVars sourced by the alternators to the power system.

But these are all mostly as applied to AC machines.
 

1. What is the difference between permanent winding and field winding?

The main difference between permanent winding and field winding is that permanent winding refers to a type of motor or generator in which the magnetic field is created by a permanent magnet, while field winding refers to a type of motor or generator in which the magnetic field is created by an electromagnet.

2. Which one is more efficient, permanent winding or field winding?

In terms of efficiency, permanent winding is generally more efficient than field winding. This is because permanent magnets have a constant magnetic field strength, while electromagnets require a continuous flow of electricity to maintain their magnetic field.

3. Can the magnetic field in a permanent winding be changed?

No, the magnetic field in a permanent winding is fixed as it is created by a permanent magnet. It cannot be changed or controlled.

4. What are the main applications of permanent winding and field winding?

Permanent winding is commonly used in small motors and generators, as well as in household appliances such as fans and electric toothbrushes. Field winding, on the other hand, is used in larger motors and generators, such as those found in cars and power plants.

5. Which type of winding is more cost-effective?

In terms of cost, permanent winding is generally more cost-effective than field winding. This is because permanent magnets are cheaper and require less maintenance compared to electromagnets used in field winding.

Similar threads

B How the Earth's Magnetic field deflects the solar wind
    • Astronomy and Astrophysics
Replies
5
Views
1K
New Materials (new china industry),could this be the next bill gates($$$) industry?
    • Materials and Chemical Engineering
Replies
4
Views
8K

Hot Threads

Recent Insights

Back
Top