Why is the DC contactor coil resistive

To put it simply, it is because the DC coil generates a reverse electromotive force when it suddenly loses power.

Electromagnetic induction), which threatens the safety of the circuit, is connected to a reverse diode or varistor.

You can release this reverse EMF.

To complicate it, the coil of the contactor generates a magnetic field when energized, and this magnetic field gathers a certain amount of energy. When the power is cut off, according to Lenz's law.

The magnetic field energy is converted into electrical energy to stop the change in electric current. Since the energy gathered by the coil is u1i1, according to the conservation of energy u1i1=u2i2, u2 will be infinitely high when i2 is infinitely low. The instantaneous high voltage can easily break down the electronic components in the DC circuit, and the diode and varistor can dissipate this part of the energy to prevent the high voltage from breaking down the electronic components.

There are very few electronic components in AC circuits, and even if they do, they are dual-conductive.

thyristors and other components, will not cause harm.

Also, you said that the model mentioned is an AC contactor.

Series, DC domestic only CZ0-250, the old product, now almost no one uses, but the toy industry uses a lot, like bumper cars.

Because it is a DC power supply, a DC contactor is used, but the style imitates Europe and the United States, the current is 200A-600A, all of which are unipolar and bipolar, ZJW series, and there are very few varistors, but Siemens' original German 3TF series, all the coils are protected by varistors and diodes, and the 3TF series of domestic Suzhou Siemens is not in the whole system, it may be that there are no clear technical requirements in China.

1.AC contactor can be used instead of DC contactor in emergency time, the suction time can not exceed 2 hours (because the heat dissipation of AC coil is worse than DC, which is determined by their different structures), it is really best to use it for a long time in the AC coil with a resistor, and DC can not replace AC contactor.

2.The number of coil turns of AC contactor is small, and the number of coil turns of DC contactor is large, and the volume of the coil can distinguish the case of excessive current of the main circuit (IE>250A), and the contactor adopts a series double winding coil.

3.The coil of the DC relay has a large reactance and a small current. If it is said that it will not be damaged when it is connected to the alternating current, it will be discharged at the right time. However, if the reactance of the coil of the AC relay is small, the current will be large, and if the coil is connected to direct current, the coil will be damaged.

4.The AC contactor has a short-circuit ring on the core, and the DC contactor should not have it in principle.

5. The core of the AC contactor is made of many layers of silicon steel sheets, because it is necessary to reduce the eddy current loss.

The core of the DC is monolithic.

6. The AC contactor is used to control the AC load, and the DC contactor is used to control the DC load, but the control coil can be AC or DC.

There is no specified value for the coil resistance, the smaller the better.

The basic components of an AC contactor are:

1. Electromagnetic system, including suction coil, moving iron core and static iron core;

2. The contact system includes three groups of main contacts and one or two groups of normally open and normally closed auxiliary contacts, which are connected with the moving iron core and are linked to each other;

3. Arc extinguishing device, the AC contactor with large capacity is generally equipped with an arc extinguishing device, so as to quickly cut off the arc and avoid burning the main contact;

4. Insulated shells and accessories, various springs, transmission mechanisms, short-circuit rings, binding posts, etc.

During the normal use of the AC contactor, the electromagnet coil has been energized to produce electromagnetic attraction, ensure the engagement of the iron core and armature, drive the dynamic and static contacts to close, and connect the circuit. In the process of use, there is resistance in the coil itself, which continuously consumes electrical energy, which is one of the main costs of the contactor, and wastes a lot of energy and property.

A 380V coil resistance is about 380 ohms, 10A 380V coil resistance is about 500 ohms, different models have different resistance values, it can be judged by comparing the time of use and normal operation.

2. AC contactors mainly include CJX2 series, CJ20 series, CJT1 series, 3TB, B series and other CJ series most commonly used products.

3. There are three commonly used arc extinguishing methods for AC contactors, double fracture arc extinguishing, longitudinal seam arc extinguishing and gate arc extinguishing, which are used to eliminate the arc generated during the opening and closing of dynamic and static contacts, and the contactor with a capacity greater than 10A is equipped with an arc extinguishing device, and the AC contactor also has auxiliary components such as reaction springs, buffer springs, contact pressure springs, transmission mechanisms, bases and terminals.

The 17th and 19th floors have really been measured? But I remember measuring about 110 ohms, which is too much of a difference, right?

The coil resistance of an AC contactor varies depending on the make and model of the contactor.

For example, the ABB AC contactor A30 series has a coil resistance of 200 400 ohms; The reason why it is a range means that even if the contactor of the same model is used, the coil resistance value is not exactly the same. Another is that the structure of the AC contactor is not as simple as imagined, and there are other structures in it, so it is of little significance to simply consider the resistance value.

Some contactors have resistor-capacitance absorption elements on the coil, so the resistance value cannot be measured, and the resistance value of the same voltage coil sometimes cannot be the same Yes, I had a long time ago, there is a capacitor in the coil and a few diodes

Some contactor coils now operate in DC to save energy to open the contactor, which may be the case if other elements are found.

Resistance 300 ohms - 1000 ohms or so.

The coil resistance of 25A 380V is about 380 ohms. The resistance of 10A 380V is about 500 ohms. The resistance value is different for different models.

The resistance value of the AC contactor coil is related to the voltage level of the coil, the higher the voltage level, the greater the resistance value, generally under normal circumstances, the resistance value is in hundreds of ohms to more than 1,000, and the comparison between the time and normal operation can be judged.

How the resistance value is calculated:

1. The resistance conversion formula is r= l s, r=u i, r=u p, r=p i, in physics, the resistance represents the size of the conductor's obstruction effect on the current, and the greater the resistance of the conductor, the greater the conductor's resistance to the current.

2. The resistance value cannot be changed, which is called a fixed resistor-sensitive limb, and the resistance value that is variable is called a potentiometer or a variable resistor. The ideal resistor is linear, i.e., the instantaneous current through the resistor is proportional to the applied instantaneous voltage. Variable resistor macros for voltage divider bridges.

The magnitude of the resistance value of a resistive element is generally related to temperature, material, length, and cross-sectional area. <>

Summary. This is determined by the working principle of the vacuum contactor. The electromagnetic circuit of the vacuum contactor should play the role of engaging and holding, so it is necessary to double coils, one group of holding, and one group of suction.

Why do DC contactors use dual coils?

This is determined by the working principle of the vacuum contactor. The electromagnetic circuit of the vacuum contactor should play the role of engaging and holding, so it is necessary to double coils, one group of holding, and one group of suction.

What is the principle of DC contactor coil series NC point and NC point?

The DC contactor adopts a modular design, which can assemble the number of contact channels required by the customer and the contact form required by the customer (normally open, normally closed and convertible) with the least number of parts; This series of products has a high contact breaking voltage, and adopts horizontal blowing magnetic field arc extinguishing, and the maximum breaking voltage can reach 220VdcThe products are suitable for program-controlled power supply or uninterruptible power supply systems, forklifts, electric vehicles, and construction machinery systems. Working principleWhen the contactor coil is energized, the coil current generates a magnetic field, so that the static iron core generates electromagnetic attraction to attract the moving iron core and drive.

Contact action: the normally closed contact is disconnected, the normally open contact is closed, and the two are linked. When the coil is de-energized, the electromagnetic attraction disappears and the armature is released under the action of the release spring, which restores the contacts: the normally open contacts are disconnected and the normally closed contacts are closed.

Depending on the contactor specification (coil voltage, contactor size, etc.), the coil resistance value is definitely different.

The coil resistance of 25A 380V is about 380 ohms, and the resistance of 10A 380V is about 500 ohms. The resistance value is different for different models. It is possible to make a judgment by comparing the time used with the normal operation.

AC contact buried wheel is mainly CJX2 series, CJ20 series, CJT1 series, 3TB, B series and other most commonly used products in CJ series.

AC contactors often use three arc extinguishing methods: double-fracture electric arc extinguishing, longitudinal seam arc extinguishing and grid arc extinguishing. It is used to eliminate the arc generated by the dynamic and static contacts in the process of splitting and closing. Contactors with a capacity of more than 10 A have arc extinguishing devices.

AC contactors also have auxiliary components such as reaction springs, buffer springs, contact pressure springs, transmission mechanisms, bases and binding posts.