Guide to choosing Aptomat

1. Concept of Aptomat

Aptomat is an electrical device that everyone must have heard of. Basically, Aptomat is a type of circuit breaker with the ability to automatically switch. In an electrical system, Aptomat has the function of protecting the system from overload or short circuit. Some models also have advanced functions such as anti-leakage or anti-shock.

2. Uses

The benefits of Aptomat are very practical. That is the reason why it has become so popular and indispensable in any electrical system. Some of the most important Aptomat benefits can be listed as follows:

• Automatically disconnect current in electrical systems when short circuit or voltage drop occurs.

• Protect electrical equipment from damage when the power system encounters unexpected problems.

• When current is leaked to ground, an imbalance between outgoing and incoming currents will occur. Aptomat will be used to disconnect power in this case.

• If an electric shock occurs, Aptomat also automatically cuts off the power to protect people.

3. Structure and working principle        

There are many types of Aptomat, but they usually have the same construction, consisting of two contact levels (main contact and arc) or three contacts (main contact, auxiliary contact and arc). When the circuit is closed, the contacts will close from the arc to the auxiliary contact and the main contact is last. If the circuit is broken, the process of opening the contacts will be reversed.        

In addition, Aptomat also has basic components such as arc extinguishing, cutting actuator and protective hook. Arc extinguishing is usually of two types, semi-closed or semi-open. The shear actuator can be manually or electromechanical controlled. Finally, protective hooks come in two types, relay or solenoid.

All Aptomat systems have the same working principle. The protection hooks will interrupt the circuit when detecting a fault condition occurs in the electrical system. If a current flowing through the contacts changes suddenly, the magnetic field generated on the spring (too low voltage) will be reduced or the spring will overheat (high voltage) causing the contacts to open and the current will be cut off.  

For Aptomats for household use (rated current is not greater than 600A), users will have to use their hands to control the device to work again. On the other hand, some Aptomat models for higher current power systems (up to 1000A) often have an electromagnetic control mechanism.              

After a short circuit has occurred for some time, the springs in the protective hook will return to normal so that the contacts can come back into contact, allowing current to continue to flow.

4. How to choose Aptomat        

The selection of Aptomat, mainly based on: calculated current flowing in the circuit; overload current; selective operability.        

In addition, the choice of Aptomat must also be based on the working characteristics of the load and the Aptomat is not allowed to cut off when there is a short-term overload (usually occurs in normal working conditions such as starting current, peak current in technological loads).        

The general requirement is that the rated current of the protection level Iap should not be less than the rated current of the circuit:Iap>=Itt        

Depending on the specific characteristics and working conditions of the load, people are guided to choose the rated current of the protective hook equal to 125%, 150% or more than the calculated current of the circuit.        

Finally, we choose Aptomat according to the manufacturer’s given technical data.

5. Example        

Choose Aptomat for a pump with a power consumption of 2kW, cosphi = 0.85 for household use?        

We have: Itt=Ptt/Udm*cos(phi)=2000/(220*0.85)=10.69


We can calculate: Ict=1,2*10.96=13.152A        

Therefore, we choose the type of Aptomat with rated current of 16A.        

Currently, Aptomat is an indispensable electrical device in industrial and civil electrical cabinets. Almost all locations must use Aptomat because of its superiority, if you are in need of design advice or installation of electrical cabinets manufactured and distributed by VESA, please contact us immediately.        

For product advice and support, please contact:        

Vietnam Water and Environmental Sanitation Co., Ltd        

Address: 2nd Floor, Building D, Viet Duc Complex, Alley 164 Khuat Duy Tien, Thanh Xuan District, Hanoi City, Vietnam        

Hotline: (+84) 904 571 488.        

Best Regards./.