Contactors
All versions can carry up to 500 amperes continuously. In the event of a short circuit, the series can withstand up to 6,000 amperes for 20 milliseconds without the contacts welding. The contactor therefore retains its full function to disconnect high power ranges up to 500 amps at 1,500 volts – regardless of current direction – if required. This fully bidirectional function is important for systems with a charging and discharging process, such as in battery networks or electric vehicles. Stationary energy storage applications:
| Isolation voltage | Up to 1 500 volt |
| Thermal current | Up to 500 amperes |
| Inrush capacity | Up to 2 500 amperes |
| Short-circuit capacity | Up to 5 000 amperes in 20 milliseconds |
A contactor is defined according to IEV ref 441-14-33 as a mechanical switching device with only one rest position, operated other than by hand, capable of switching on, conducting and breaking currents under normal circuit conditions including operational overload.
In common parlance, this usually refers to an electromechanical contactor where the operation of switching on and off is done by means of an electrically driven coil. Simply put, the contactor is essentially a switch for electrical power in the same way that a relay is a switch for electrical signals or small loads.
With electrification and higher voltages in systems, contactors capable of extinguishing the resulting arc are required to safely interrupt the current, even under load in an emergency. It is therefore important to have the right contactor for the purpose. Factors to consider when choosing a contactor are current, voltage, current direction, inductance, short-circuit current, etc. This is to ensure that the current is actually broken and does not lead to more catastrophic events such as fire or similar, read more about risks here. Please contact us for help in choosing a contactor for your system.
See our range of contactors and contacts here
For each contactor, there is a short-circuit current and a time that it must withstand. If this is higher and longer than the specification, there is a risk that the contactor will weld together. What happens is that the magnetic field in the contact bridge forces the contact bridge apart and small arcs can form with the subsequent risk of the contactor welding the contact bridge. Alternatively, the heat in the contact points can be so high that they melt together.
Historically, contactors have been used to directly switch on and off electrical loads, such as electric motors, and even today they are used this way in many applications. In modern systems, however, starting and stopping is often done electronically and the purpose of the contactor is mainly to enable galvanic separation and to act as a switch in the event of an abnormality or fault in the system.
In each contactor there is a coil that operates switching and breaking, the voltage to control the coil can vary depending on the application, normally in industry is 24VDC. The contactor may also contain a PCB that controls switching on and off. Some contactors have more than one coil to reduce power consumption. Usually one more powerful to close the plug and one that draws less current to keep the plug closed. This has in modern Schaltbau contactors often been replaced by only one coil controlled by PWM signal to achieve lower power consumption and lighter contactor.
High short-circuit currents and an unregulated closing with load is the most common reason for the contactor to weld. This is usually due to an insufficient pre-charge. Read more about Pre-charge here.
Excessive and high short-circuit currents can cause the contact bridge to lift and open due to the magnetic field generated by the current, called levitation. This can cause the contactor to weld because when the contactor bridge opens, micro arcing and extensive heating occur.
Breaking higher loads than the contactor is designed for, especially high inductance can cause the contactor bridge to weld.
Using silver oxide on the contactor pills increases the resistance to welding.
Read more about our contactors here.
When breaking both + & and – in case of anomalies in the system.
This question must be broken down into several parameters. The amount of current that can flow through the contactor continuously is determined by the heat dissipation capacity and the maximum continuous current is often referred to as Ith or thermal current. Often a higher current can be run for a shorter time.
When switching off or breaking under load, an arc is always created. The energy in the arc is determined by the current and voltage and the type of load being broken. The arc is ionized gas, s.k. plasma. The energy of the arc is very high and powerfully destructive for the e.g. the contacts. Depending on the design, the contactor can handle the arc in different ways. The aim is always to cool the energy in the arc to create a safe situation and reduce wear and tear. The breaking capacity is always given in amperes at a specific voltage and time constant of the load.
When switching under load, small arcs may form but these disappear as soon as the contact is closed. The capacity for switching is often much greater than for breaking and is given in amperes at a specific voltage and time constant for the load.
When an electromechanical component such as a contactor is exposed to a situation that causes it to fail, it does so safely. A contactor that has arc extinguishing in air will be able to break the current without damaging other components. In gas-filled and contactors with closed arcing chambers, there is a risk of large pressure differences occurring due to. heating, this can lead to explosions with uncontrolled consequences, e.g. current conductors can risk damaging surrounding components.
Vacuum contactors use encapsulated contacts with vacuum instead of air as the medium to eliminate arcing. Vacuum contactors are only applicable for use in AC applications. The AC arc generated by the opening of the contacts will itself be extinguished at the zero crossing of the current waveform, the vacuum preventing a re-ignition of the arc across the open contacts.
The contactor can either be controlled to one mode or both modes, for switching on or off. For example, a monostable controls the switch-on by coil, while the switch-off is controlled by a spring if the coil voltage is broken. A bistable controls both striking and breaking with the coil. A bistable contactor uses no energy to keep the contactor in the respective position.
Read more about our contactors here.
NO = Normally Open, NC = Normally Closed. This describes the state of a contactor when the voltage in the system is off. Normally open (NO) is mostly used in electrical systems where, for safety reasons, you want to be sure that the contactor opens when the power is cut in the system in case of a power failure. Normally Closed (NC) is often used when you want to be sure that the contactor closes a circuit in the event of a voltage drop, such as a power failure. to drain the system of energy to earth.
Read more about our DC contactors for both high and low voltage here.
An economizer is an electronic circuit that regulates (PWM) the turn-on power and hold power of the coil. An economizer also regulates the stroke to reduce contact bounce. Reduced contact resistance results in a longer service life, especially for loaded strikes.
A contactor is a vital safety component in any electrical system, Schaltbau stands for new patented technology. By far the longest life cycle, resulting in a low price. The patented open arc chamber technology will be larger in volume. Achieving the highest level of safety requires longevity, technical innovation and documented approval.
Contactors
Contactors
Contactors
Contactors
Contactors
Contactors
Contactors
Contactors
Schaltbau’s new C300 series super-compact bidirectional DC contactors switch high power in a very small space. With a switching capacity of up to 2,500 amps, this extremely compact series is suitable for applications with high inrush currents or high capacitances. All versions can carry up to 500 amps continuously. In the event of a short circuit, even 5000 amps can flow for 20 milliseconds without the contacts welding.