Electronic ballasts, modern LED lighting, energy-saving lamps and power supplies typically have high inrush currents when switching, which can be up to 250 times the nominal current. ComatReleco offers special relays for high inrush currents:

• CHI14 / CHI34: Zero-crossing switching, up to 800A inrush current for 800us
• C7-W10: With tungsten pre-contact, up to 500A inrush current for 2.5ms
• C10-A15: With silver-tin oxide contact, up to 120A inrush current for 20ms
• CIM14: Time relay with zero-crossing switch, up to 800A inrush current for 800us

The series connection of a resistor and a capacitor causes the current to decay in a damped oscillation during the switch-off process. During the switch-on process, the resistor prevents the full capacitor charge from discharging via the switch contact. The protective circuit using an RC element is very well suited for alternating voltage. In addition, there is an immediate switch-off limitation.

A reliable three pole LED step switch can be implemented with the CHI34/UC24-240V together with the CIM1/UC24-240V. The CIM1 manages the step logic. The CHI34 is designed for modern LED systems and ensures stable switching of the lighting.

Coil voltage?

• Available coil voltages AC and DC can be found in the catalogue. ComatReleco's technical support team can help you if you cannot find a suitable coil voltage for your application.

Load to be switched?

• Type of load?
  • Is the load to be switched ohmic? Inductive? Capacitive? This is a very important factor to know when selecting a relay/contactor.
• AC? DC?
  • Is the load to be switched supplied with alternating current or direct current? How high is the voltage?

Switching frequency?

• How often should the relay be switched per day, hour, minute or even second? For many switching cycles, a semiconductor relay is recommended, as there is no mechanical contact and the service life is therefore practically infinite.

Environment?

• This includes, for example, the ambient temperature where the relay/contactor is installed. It also includes information about the environment: dusty? Does moisture penetrate? Aggressive gases? Other factors worth mentioning?

Switching small signals – what should be considered?

• If signals in the mA range are to be switched, it is important to select a suitable relay with an appropriate minimum load. Relays with gold-plated contacts are suitable for this purpose. Gold has very good conductivity, which is why small signals can be switched. However, gold tends to weld the contacts when currents are too high. ComatReleco also offers relays with double gold contacts. These double contacts ensure increased switching reliability for control and signal circuits.
• Another alternative to mechanical relays is the use of semiconductor relays. The CSS series from ComatReleco can reliably switch currents from as low as 1 mA (DC) and 35 mA (AC).

Free wheeling diodes protect against voltage spikes when the supply current of an inductive DC load is suddenly switched off. To this purpose the diodes are connected parallel to the inductive DC consumers, so that they are used by the supply voltage in theblocking direction. Afrer the supply current has been switched off the self-induction of the coil ensures that the current continues to flow in the original direction. Without a free wheeling diode, this would result in a voltage spike that adds to the operating voltage and could damage or destroy the switching path. However, with a free wheeling diode, the voltage spike is limited to the forward voltage of the diode (for silicon about 0.7 V). This protects the electronic components, but also the switching contacts, very effectively against voltage spikes.