To install the connector, follow these steps:
1. Prepare the components for terminal block installation by removing power from the CPU and opening the cover for the terminal block.
2. Align the connector with the pins on the unit.
3. Align the wiring edge of the connector inside the rim of the connector base.
4. Press firmly down and rotate the connector until it snaps into place.
Check carefully to ensure that the connector is properly aligned and fully engaged.
2.2 Wiring guidelines
Proper grounding and wiring of all electrical equipment is important to help ensure the optimum operation of your system and to provide additional electrical noise protection for your application and the S7-1200. Refer to the technical specifications (Page 289) for the S7-1200 wiring diagrams.
Prerequisites
Before you ground or install wiring to any electrical device, ensure that the power to that equipment has been turned off. Also, ensure that the power to any related equipment has been turned off.
Ensure that you follow all applicable electrical codes when wiring the S7-1200 and related equipment. Install and operate all equipment according to all applicable national and local standards. Contact your local authorities to determine which codes and standards apply to your specific case.
WARNING
Installation or wiring the S7-1200 or related equipment with power applied could cause electric shock or unexpected operation of equipment. Failure to disable all power to the S7-1200 and related equipment during installation or removal procedures could result in death, severe personal injury, and/or damage due to electric shock or unexpected equipment operation.
Always follow appropriate safety precautions and ensure that power to the S7-1200 is disabled before attempting to install or remove the S7-1200 or related equipment.
Always take safety into consideration as you design the grounding and wiring of your S7-1200 system. Electronic control devices, such as the S7-S7-1200, can fail and can cause unexpected operation of the equipment that is being controlled or monitored. For this reason, you should implement safeguards that are independent of the S7-1200 to protect against possible personal injury or equipment damage.
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Installation 2.2 Wiring guidelines
WARNING
Control devices can fail in an unsafe condition, resulting in unexpected operation of controlled equipment. Such unexpected operations could result in death, severe personal injury and/or property damage.
Use an emergency stop function, electromechanical overrides, or other redundant safeguards that are independent of the S7-1200.
Guidelines for isolation
S7-1200 AC power supply boundaries and I/O boundaries to AC circuits have been designed and approved to provide safe separation between AC line voltages and low voltage circuits.
These boundaries include double or reinforced insulation, or basic plus supplementary insulation, according to various standards. Components which cross these boundaries such as optical couplers, capacitors, transformers, and relays have been approved as providing safe separation. Isolation boundaries which meet these requirements have been identified in S7-1200 product data sheets as having 1500 VAC or greater isolation. This designation is based on a routine factory test of (2Ue + 1000 VAC) or equivalent according to approved methods. S7-1200 safe separation boundaries have been type tested to 4242 VDC.
The sensor supply output, communications circuits, and internal logic circuits of an S7-1200 with included AC power supply are sourced as SELV (safety extra-low voltage) according to EN 61131-2.
To maintain the safe character of the S7-1200 low voltage circuits, external connections to communications ports, analog circuits, and all 24 V nominal power supply and I/O circuits must be powered from approved sources that meet the requirements of SELV, PELV, Class 2, Limited Voltage, or Limited Power according to various standards.
WARNING
Use of non-isolated or single insulation supplies to supply low voltage circuits from an AC line can result in hazardous voltages appearing on circuits that are expected to be touch safe, such as communications circuits and low voltage sensor wiring.
Such unexpected high voltages could cause electric shock resulting in death, severe personal injury and/or property damage.
Only use high voltage to low voltage power converters that are approved as sources of touch safe, limited voltage circuits.
Guidelines for grounding the S7-1200
The best way to ground your application is to ensure that all the common and ground connections of your S7-1200 and related equipment are grounded to a single point. This single point should be connected directly to the earth ground for your system.
All ground wires should be as short as possible and should use a large wire size, such as 2 mm2 (14 AWG).
When locating grounds, consider safety-grounding requirements and the proper operation of protective interrupting devices.
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Installation
2.2 Wiring guidelines
Guidelines for wiring the S7-1200
When designing the wiring for your S7-1200, provide a single disconnect switch that simultaneously removes power from the S7-1200 CPU power supply, from all input circuits, and from all output circuits. Provide over-current protection, such as a fuse or circuit breaker, to limit fault currents on supply wiring. Consider providing additional protection by placing a fuse or other current limit in each output circuit.
Install appropriate surge suppression devices for any wiring that could be subject to lightning surges.
Avoid placing low-voltage signal wires and communications cables in the same wire tray with AC wires and high-energy, rapidly switched DC wires. Always route wires in pairs, with the neutral or common wire paired with the hot or signal-carrying wire.
Use the shortest wire possible and ensure that the wire is sized properly to carry the required current. The connector accepts wire sizes from 2 mm2 to 0.3 mm2 (14 AWG to 22 AWG).
Use shielded wires for optimum protection against electrical noise. Typically, grounding the shield at the S7-1200 gives the best results.
When wiring input circuits that are powered by an external power supply, include an overcurrent protection device in that circuit. External protection is not necessary for circuits that are powered by the 24 VDC sensor supply from the S7-1200 because the sensor supply is already current-limited.
All S7-1200 modules have removable connectors for user wiring. To prevent loose connections, ensure that the connector is seated securely and that the wire is installed securely into the connector. To avoid damaging the connector, be careful that you do not over-tighten the screws. The maximum torque for the connector screw is 0.56 N-m (5 inch-pounds).
To help prevent unwanted current flows in your installation, the S7-1200 provides isolation boundaries at certain points. When you plan the wiring for your system, you should consider these isolation boundaries. Refer to the technical specifications for the amount of isolation provided and the location of the isolation boundaries. Do not depend on isolation boundaries rated less than 1500 VAC as safety boundaries.
Guidelines for inductive loads
You should equip inductive loads with suppression circuits to limit voltage rise when the control output turns off. Suppression circuits protect your outputs from premature failure due to the high voltages associated with turning off inductive loads. In addition, suppression circuits limit the electrical noise generated when switching inductive loads. Placing an external suppression circuit so that it is electrically across the load, and physically located near the load is most effective in reducing electrical noise.
Note
The effectiveness of a given suppression circuit depends on the application, and you must verify it for your particular use. Always ensure that all components used in your suppression circuit are rated for use in the application.
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Installation 2.2 Wiring guidelines
Control DC inductive loads
A B
① l1N4001 diode or equivalent
② 8.2 V Zener (DC outputs), 36 V Zener (Relay outputs) S7-1200 DC outputs include suppression circuits
that are adequate for the inductive loads in most applications. Since the relays can be used for either a DC or an AC load, internal protection is not provided. The following figure shows a sample suppression circuit for a DC load.
In most applications, the addition of a diode (A) across the inductive load is suitable, but if your application requires faster turn-off times, then the addition of a Zener diode (B) is recommended.
③ Output point
Be sure to size your Zener diode properly for the amount of current in your output circuit.
Relay outputs that control AC loads
When you use a relay output to switch 115 V/230 VAC loads, place resistor/capacitor networks across the AC load as shown in this figure. You can also use a metal oxide varistor (MOV) to limit peak voltage. Ensure that the working voltage of the MOV is at least 20% greater than the nominal line voltage.
③ Output point
Guidelines for lamp loads
Lamp loads are damaging to relay contacts because of the high turn-on surge current. This surge current will nominally be 10 to 15 times the steady state current for a Tungsten lamp.
A replaceable interposing relay or surge limiter is recommended for lamp loads that will be switched a large number of times during the lifetime of the application.
长沙工控帮教育科技有限公司整理
Installation
2.2 Wiring guidelines
长沙工控帮教育科技有限公司整理