Relay Output
It is the output type in which the receiver delivers the command by converting it into an electromechanical contact. The output does not generate a voltage, it only closes or opens an external circuit. On the LF100R receiver this output is offered as two contacts rated 2×10A, with the capacity to drive the forward-reverse direction of a DC motor without a contactor.
The greatest advantage of a relay output is that it is independent of the voltage and type of the circuit to be connected: the same contact can switch a 24V DC coil as well as a 220V AC control line. The price is mechanical life; the contact wears a little with every switching operation.
When sizing the output, distinguish three things:
- The catalogue ampere rating is generally for a resistive load (AC-1). On inductive loads such as a contactor coil, the applicable capacity falls noticeably.
- The inrush current is far above the continuous value. On inductive AC loads, roughly 10 times the current is assumed at the first instant.
- The arc at the moment of breaking determines the life. A freewheeling diode on a DC coil and an arc suppression measure on an AC coil extend contact life.
The application rule is clear: on small loads the relay can drive directly, whereas on large crane motors connect the relay not to the motor but to the contactor coil and let the contactor carry the motor current. The relay ampere rating of the ST100 4-channel and the ST200 variants is not stated in the product data; do not assume 10A on those products.
The context in which this term is used: Wireless remote control installation: pairing, relays, safety