1. How to select safety relay?

According to the different input equipment of the safety circuit, the safety relay is selected from five aspects: input equipment, number of output channels, back-end drive capacity requirements, safety level and functional requirements. The input equipment of mechanical safety circuit is usually safety sensor, mainly including emergency stop button, safety door, safety screen, safety pad, interlock device, two hand button, laser scanner, etc.

2. What are the common faults and solutions of safety relay?

The safety relay disconnects the circuit in use. At this time, it needs to be accurately judged whether the safety relay is broken or the safety relay has detected unsafe factors and disconnected the circuit.

① If there are potential safety hazards in the circuit, restart the safety relay and restore the circuit after eliminating the potential safety hazards. For example, the SIS system pulse detection leads to the frequent disconnection and startup of the safety relay. Adjust the duration of the SIS system pulse detection low level so that it will not be recognized by the safety relay.

② If the safety relay fails, there are usually the following treatment methods:

a. The output contact of the safety relay is generally protected by the contact fuse. During use, the fuse may be blown due to short circuit or overcurrent, and the safety relay cannot start the field equipment. Action: replace the fuse.

b. The internal components of the safety relay are damaged due to overvoltage in the control circuit of the safety relay. Measures: replace the safety relay and contact the manufacturer for maintenance or replacement.

3. Is it necessary to use safety relays on mechanical equipment?

The mandatory standards for safety requirements of domestic equipment are not high, or there is no corresponding standard certification, such as ce of the European Union. When the equipment is in danger of personal injury or property damage, use safety relays. It does not enter the PLC, but uses hardware to disconnect the power supply, so that the equipment is completely shut down; Moreover, the safety relay itself also has several contacts to ensure effective disconnection in case of fault. If your equipment wants to enter other countries, it must have CE certification at least. There will be problems in this regard. Therefore, some equipment that needs to be exported is usually equipped with safety relays, especially in the European Union and Japan.

Of course, with the increasing attention to safety in China, some technical standards and implementation will gradually integrate with the world. In the 13th five year plan for safety related standardization work, it is mentioned that the updating and upgrading of machinery safety related standards and the strengthening of implementation will make the requirements related to safety circuit design more and more stringent. At this time, as a forward-looking equipment manufacturer, is it necessary to use safety relays? Do we need to say more?

4. What is automatic start of safety relay?

Automatic start, as long as the opening conditions are met (the sensor and feedback circuit are closed), the device will automatically open the starting circuit.

5. How much capacitance should be installed in the control circuit of the safety relay?

The coil shunt capacitance of ordinary relay is to prevent the high voltage at both ends of the relay coil from breaking through the contact of the relay and generating arc, but because of the increase of capacitance, the action delay of the relay will increase. Therefore, most relay applications now use freewheeling diodes to remove arcs. The safety relay is an electronic module with a freewheeling diode inside to remove the arc. In practical use, there is no need to install capacitors.