Magnets are pieces of metal that have the ability to attract other metals. Every magnet has two poles: a north and a south. Much like electrical charges, two similar magnetic poles repel each other; while opposite magnetic poles attract each other. Magnets have a continuous force around them that is known as a magnetic field. This field enables them to attract other metals. Figure 1 illustrates this force using bar and horseshoe magnets.
A system such as a nucleus may consist of many particles coupled together so that in any given state, the nucleus possesses a total magnetic moment and a total angular momentum J. Two vectors may be taken as parallel.
AC motors convert AC electrical energy to Mechanical energy. AC motors:
the armature of rotor is a magnet (different to DC motors).
the stator is formed by electromagnets (like in DC motors). Effects of AC Supply on Magnetic Poles Consider the rotor to be a permanent magnet.
Current flowing through conductors energize the magnets and develop N and S poles.
The strength of electromagnets depends on current.
First half cycle current flows in one direction.
Second half cycle it flows in opposite direction...
Attract, force, gravity, magnet, pole, repel, speed, vibrate,... là những từ vựng được tác giả Natalie Goldstein giới thiệu đến trong cuốn sách "Making music". Mời các bạn cùng tham khảo để có thêm tài liệu phục vụ nhu cầu học và dạy tiếng Anh cho trẻ em.
Attract, force, gravity, magnet, pole, repel, speed, vibrate là những từ vựng được tác giả Carol Levine giới thiệu đến trong cuốn sách "Forces and Sounds". Mời quý phụ huynh và các bạn cùng tham khảo để có thêm tài liệu phục vụ nhu cầu dạy tiếng Anh cho trẻ.
The earth's magnetic field has two magnetic poles. These magnetic poles are
the magnetic South Pole and North Pole.
The earth's magnetic poles are located at approximately 12° offset from the
earth's geographical poles. At the magnetic North Pole, the gridlines of the
magnetic field are vertical to the earth's surface. The needle of a compass, for
example, will point to this magnetic pole.
At the magnetic South Pole, the magnetic lines leave the earth’s surface. The
earth’s magnetic field does not run parallel to the earth’s surface.
Attract, force, gravity, magnet, pole, repel, speed, vibrate là những từ vựng được tác giả Heidi Gillis giới thiệu trong cuốn sách "Movement and Sound". Mời các bạn cùng tham khảo nội dung cuốn sách để có thêm tài liệu phục vụ nhu cầu học tập và giảng dạy.
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Brushless DC (BLDC) motors are synchronous motors with permanent magnets on the rotor and armature windings on the stator. Hence, from a construction point of view, they are the inside-out version of DC motors, which have permanent magnets or ﬁeld windings on the stator and armature windings on the rotor. A typical BLDC motor with 12 stator slots and four poles on the rotor is shown in Fig. 10.1. The most obvious advantage of the
Scientists still do not know exactly what causes the earth’s magnetic field. In the 16th century, it was believed that a mountain of magnetite (a magnetic mineral) was located at the North Pole and that this mountain caused the earth’s magnetic field. English physician William Gilbert was the first to propose, in 1600, that the earth itself was a massive magnet. Current theories hold that the earth’s magnetic field is created by currents within the liquid outer core of the earth, which is composed mostly of iron.
The speed of the rotating magnetic field 2πf1 ωsyn = P/2 60f1 nsyn = P/2 (rad/s) (rev/min)
where f1 is the frequency of the stator current, and P the number of poles. 2. The rotor speed of an induction machine is generally different from the speed of the rotating magnetic field. The percentage difference of speed, known as slip, is defined as s= ωsyn-ωm nsyn-n = n ωsyn syn
where ωm and n are the speed of the rotor in rad/s and rev/min, respectively. 3. The induced emf in one phase of the stator winding is E1 = 4.44f1N1kw1Φm and...
Flux and Voltage Induction Machines 6.1 Description 6.2 Concept of Operation 6.3 Torque Development 6.4 Operation of the Induction Machine near Synchronous Speed 6.5 Leakage Inductances and their Effects 6.6 Operating characteristics 6.7 Starting of Induction Motors 6.8 Multiple pole pairs Synchronous Machines and Drives 7.1 Design and Principle of Operation 7.1.1 Wound Rotor Carrying DC 7.1.2 Permanent Magnet Rotor 7.2 Equivalent Circuit 7.3 Operation of the Machine Connected to a Bus of Constant Voltage and Frequency 7.4 Operation from a Source of Variable Frequency and Voltage...
This chapter include all of the following content: Introduction to polyphase synchronous machines, synchronous – machine inductances and equivalent circuits, performance characteristics, effects of salient poles, power – angle characteristics of salient – pole machines, permanent – magnet ac motors.