The selection of ac contactor should meet the requirements of the controlled equipment, and the rated working voltage must be the same as the rated voltage of the controlled equipment. In addition, the load power, use category, operation frequency, working life, installation mode and size, and economy of the controlled equipment are the basis for selection. So, let's look at the selection of AC contactor.
Series and parallel use of AC contactor
Since most power consumption devices are single-phase loads, multipole AC contactors can be used in parallel. Resistance furnace, welding transformer, etc. When several poles are used in parallel, a small capacity AC contactor can be selected. However, it must be noted that the constraint heating current of the AC contactor is not completely proportional to the number of parallel poles. Because of the positive effect, the resistance values of the electrostatic contact circuit are not necessarily equal, so the positive flow of current is not evenly distributed. Therefore, the parallel current only increases by 1.8 times, and the parallel three-pole current only increases by 2-2.4 times.
In addition, it should be noted that all pole contacts of parallel connection cannot be connected and disconnected at the same time, so the on-off capacity cannot be improved.
In some cases, several poles of ac contactor can be used in series, and the increase of contact fracture can divide the arc into multiple stages, which improves the arc extinguishing ability and accelerates the arc extinguishing. Therefore, several poles in series can increase the working voltage, but do not exceed the rated insulation voltage of the AC contactor. The constraint heating current and rated operating current of the contactor connected in series remain unchanged.
Influence of power frequency
For the main circuit, the skin effect is affected by the change of frequency, and the skin effect is increased by high frequency, while for many products, 50 hz and 60 Hz have little effect on the temperature rise of the conductive circuit. However, attention needs to be paid to the attraction coil. When a 50 hz attraction coil is applied to 60 Hz, the magnetic flux of the electromagnetic line is reduced and the attraction is also reduced. Availability depends on design abundance. Generally speaking, use according to its calibration value, place an order according to the operating power frequency used when placing an order.
Influence of operating frequency
The number of operating cycles per hour of ac contactor has a great influence on the burning loss of the contactor. Please note that the applicable operating frequency is recorded in the technical parameters of ac contactor. When the actual operating frequency of electrical equipment is higher than the specified value, the contactor must be used with lower capacity.
Control the selection of AC contactor for electric heater
This kind of equipment has resistance furnace, temperature control heater, etc., this kind of load current fluctuation range is small, according to the use category is divided into AC-1, contactor control this kind of load is simple, operation is not frequent. Therefore, when selecting the contactor, as long as the heating current Ith is more than 1.2 times of the working current of the heating equipment according to the contract of the contactor. Try to use contactor control 380V, 15KW three-phase Y connection resistance furnace.
There are many types of lighting devices. The startup current and startup time vary with the type of lighting devices. This type of load is used in class AC-5A or AC-5B. If the starting time is short, the constraint heating current Ith is equal to 1.1 times of the operating current Ie of the lamp. If the starting time is long and the power factor is low, the constraint heating current greater than the operating current of the lamp can be selected.
The above is the selection of AC contactor, if you need to know more, you can contact us at any time! Our company has many years of experience, looking forward to your joining at any time.
Add: FuRong Industrial Zone，YueQing City, ZheJiang Province, China