What is an electromagnet?
An electromagnet is a component that converts electromagnetic energy into mechanical energy, which is divided into a direct current electromagnet and an alternating current electromagnet.
(1) The structure principle of AC electromagnet
AC electromagnet can be regarded as a inductive load in series of resistors and inductors. Its structure is made up of coils, yokes (static iron cores) and armature (moving iron core).
In order to reduce the iron loss, the yoke and armature are all laminated by silicon steel sheet. The coil is wound on the skeleton with enameled wire, wrapped outside the insulation protection layer, and is made after being dipped and dried and fixed on the yoke.
Alternating magnetic field is generated around the coil after alternating current. The magnetic yoke and armature are magnetized at the same time by alternating magnetic field, different polarity poles appear on the pole of the armature and the magnetic yoke, and the armature is sucked to the yoke according to the principle of same-sex repulsion and opposites attracting, until they match each other. Although the direction of the coil current is constantly changing, the direction of suction is always the same as the polarity of the armature and the yoke changes at the same time. Because the alternating current continuously assumes the sine change, when the current passes through the zero value, the suction of the electromagnet is zero, and then the armature will be released; the current is over zero, and the armature is sucked by the suction. In this way, with the constant change of alternating current, the armature will constantly be sucked and released, which is bound to produce violent vibration. In order to prevent this phenomenon, a copper ring is embedded on the polar surface of the magnetic yoke, which is called short circuit ring. The function of the short circuit ring is that when the alternating flux passes through the short circuit ring, the induced current is generated, which prevents the original magnetic field from vanishing when the alternating current passes through zero, a fixed suction force is maintained between the armature and the yoke, thus eliminating vibration at work. Because of the existence of remanence, the armature is sucked, and the method of leaving the demagnetization gap eliminates the phenomenon that the armature is sucked up after the power supply is cut off.
(2) The structure principle of the DC electromagnet.
DC electromagnet consists of a coil, a yoke and a armature. As it is known, the yoke and armature are made of magnetically conductive soft steel because of the direct current and no eddy in the yoke and armature. After the DC electromagnet is connected to the power supply, the magnitude of the current (exciting current) in the coil is independent of the core condition, which is equal to the voltage divided by the resistance of the coil. The intensity of the magnetic field is affected by the size of the current and the number of turns. The larger the current, the stronger the magnetic field; the more the number of turns, the stronger the magnetic field. The DC electromagnet has stable suction force, no noise and small vibration after the suction, so the failure rate is small.
This article is from Allicdata Electronics.