Tag: safety relay

Safety relay has special color, generally yellow. Current safety relay acts reliably and flexibly, it's mainly used to control the power supply circuit. When an emergency occurs, the circuit controlled by the safety relay is disconnected by pressing the emergency stop switch, thus ensuring safety.

Safety relay is the main component of electric locomotive control circuit and monitoring protection system. When the electrical components or connection wires in the main circuit or auxiliary circuit break as the electric locomotive is running, the safety relay of corresponding monitoring protection system can transfer the fault into electric signal. On one hand, the electric signal will be fed back to the opening coil of main breaker to trip the main breaker, thus cutting off general power supply of the electric locomotive to protect it. On the other hand, the electric signal will be fed back to signal device (including mechanical signal and electrical signal) and make it to display different fault conditions, thus guiding the electric locomotive conductor to deal with faults timely and correctly. In this respect, the safety relay doesn't directly control the main circuit or auxiliary circuit, but it's of great importance to the electric locomotive.

Measure coil resistance, resistance of a power relay coil can be measured with the R×10Ω band, thus judging whether the coil has open circuit. Measure actuation voltage and actuation current, with an adjustable stabilized voltage supply and ammeter, the power relay can be input with a voltage while the ammeter can be connected in series to monitor. Slowly increase the power supply. Voltage and record the actuation voltage and actuation current when the power relay is attracted. For accuracy, more operations can be repeated to get the average value. Measure release voltage and release current, connect wires as the test above. When the power relay is attracted, reduce the power supply voltage slowly and record the voltage and current as hearing the relay to release again. More operations can be repeated to get the average value.

Safety relay can be classified into electromagnetic safety relay, thermal reed relay and solid-state relay. The working principle of safety relays can also be roughly divided into three types. Safety relay is composed of several relays and circuits, so as to supplement each other's abnormal defects and achieve the complete function of relay with correct and low faulty operation, so as to make the error and failure value become lower, thus reaching higher safety factor. Therefore, multiple safety relays should be designed to protect different grades of machinery. It is used to mainly protect the mechanical operators who perform operation under different levels of risk.