Siemens: How to Design a Programmable Logic Controller (PLC) Panel

PLC / Automation application design workspace

Application Requirements

Design a panel with an S7-1500 PLC system with the following requirements:

  • 480VAC 3 phase power to the panel
  • Indoor wall mount panel
  • Main circuit breaker with handle
  • (20) 24 VDC inputs
  • (22) 24 VDC outputs
  • (9) 4-20 ma inputs
  • (4) 4-20 ma outputs
  • 9” touch panel with data logging capabilities
  • Software and programming/communication cables,
  • All required terminal blocks, power supplies, and 120 VAC service outlet
  • Recommended wire and wireway
Example PLC Panel Layout, based on given application requirements

Selection Process and Components:

PLC

CPU

The CPU is the “brains” of the PLC

Select the CPU based on complexity of the application, and required interfaces. (Selection of the CPU is not always based on discrete attributes, please contact an AWC engineer for the best CPU for your application)

Select CPU1511-1PN

Part Number: 6ES75111AK010AB0

Memory Card

A memory card is required for an S7-1500 CPU. The PLC program is stored on the MMC. A generic SD Card can NOT be used!

Select the memory card based on the AWC Best practice of at least double the internal memory of the PLC (150kB)

Select 4MB memory card

Part Number: 6ES79548LC020AA0

Digital Inputs

Digital Inputs are input signals that are either “On” or “Off” (pushbuttons, proximity sensors, selector switches, etc…)

Select Digital Input modules based on input voltage and number of inputs. Divide number of inputs required by number of inputs per module to determine how many modules you need.

Select qty 1 of a 32 input, 24 VDC input module.

Part Number: 6ES7521-1BL00-0AB0

Select equal number of listed required front connector

Part Number: 6ES7592-1AM00-0XB0

Digital Outputs

Digital Outputs are output signals that are either “On” of “Off” (pi-lot lights, contactors, etc…)

Select Digital Outputs based on output voltage, output current, and number of output per module. Divide number of outputs required by number of outputs per module to determine how many modules you need.

Select qty 1 of a 32 output 24 VDC outputs module.

Part Number: 6ES7522-1BL01-0AB0

Select equal number of listed required front connector

Part Number: 6ES7592-1AM00-0XB0

Analog Inputs

Analog Inputs are input signals that are continuously variable. They provide a “range” of values. (Pressure Transmitter, Thermo-couple, ultrasonic sensor)

Select Analog Inputs based on type of signal and number of inputs per module

Select qty 2 of an 8 input 4-20mA module

Part Number: 6ES7531-7KF00-0AB0

Select equal number of listed required front connector

Part Number: 6ES7592-1AM00-0XB0

Analog Outputs

Analog outputs are output signals that are continuously variable. They provide a “range” of values (Valve positioner, VFD Speed setpoint)

Select Analog outputs based on type of signal and number of out-puts per module

Select qty 1 of a 4 output 4-mA module

Part Number: 6ES7532-5HD00-0AB0

Select equal number of listed required front connector

Part Number: 6ES7592-1AM00-0XB0

System Power Module / Power Supply

The system power module is essentially a 24VDC power supply in an S7-1500 form factor. A standard form factor power supply can also be used.

Size the system power module by determining the total current load of all 24VDC devices in the panel (each PLC component re-quires in the S7-1500 rack requires 24VDC power). Our HMI also requires 24VDC

.7A (CPU) + .04A (DI) + 0.06A (DO) + 2 x 0.24A (AI) + 0.19A (AO) 0.75A (HMI) + 0.07A (Ethernet Switch)= 2.29A

Select 3A Power Supply

Part Number: 6EP1332-4BA00

Bus Extension Power Supply Module

The S7-1500 system also utilizes a backplane power system to power the modules attached to the CPU. The CPU has a finite amount of power it can supply to the backplane. The bus exten-sion power supply module allows for more power to be supplied to the backplane, if your application has more modules than the CPU can power.

To determine if you need additional backplane power, calculate the sum of all backplane power consumption in your rack:

1W (DI) + 1.5W (DO) + 2 x 0.7W (AI) + 0.6W (AO) = 4.2W

The selected CPU has an output of 10W, so we do not need a bus extension module

S7-1500 Mounting Rail

S7-1500 components mount onto specific rail.

Select the necessary length of rain for the number of components selected.

Select 19” rail

Part Number: 6ES7590-1AE80-0AA0


HMI / Touch Panel

Select an HMI / Touch Panel based on size, and capabilities (Power Tags – Power Tags are the number of tags that can be read from / written to between the PLC and HMI, Data Logging).

Select the TP900 (our application requires Data logging)

Part Number: 6AV2124-0JC01-0AX0


Software

Select the appropriate software for the PLC and HMI using the Software Selection Guide

Select Step 7 Professional V16 for the S7-1500 PLC

Part Number: 6ES78221AA060YA5

Select Software Update Service Step 7 Professional

Part Number: 6ES78221AA000YL5

Select WinCC Comfort V16 for the TP900

Part Number: 6AV2101-0AA05-0AA5

Select Software Update Service for WinCC Comfort

Part Number: 6AV2101-0AA05-0AA5


Communications Cables

All of the networked devices in our panel (CPU and HMI) will be connected via Profinet. The S7-1500 CPU is also programmed over ethernet, so we will not need any special programming de-vice / cables, just ethernet from our computer.

Select Industrial Ethernet cable based on ethernet standard. AWC best practice recommends Cat 6.

Part Number: 6XV1878-2A

If you do not already have one, select an Ethernet FastConnect tool. This tool allows for easy stripping of the ethernet cable to prepare it for the ethernet plug.

Part Number: 6GK1901-1BB11-2AA0

Select Qty 2 – RJ45 Plugs for each ethernet device. Match the standard to the cable being used.

Part Number: 6GK1901-1GA00


Ethernet Switch

An ethernet switch allows multiple devices to be connected to the same network via ethernet. It is a good practice to include an ethernet switch in a PLC panel with ethernet connected devices.

Select an ethernet switch based on type, and number of ports.

Since there are no specific networking requirements for this ap-plication, select an unmanaged switch with 5 RJ45 ports.

Part Number: 6GK5005-0BA00-1AB2


120 VAC Service Outlet

A 120VAC service outlet inside of the panel, provides an easy place for a maintenance engineer to plug in a laptop while work-ing on a machine.

Part Number: 0804155


Control Power Transformer (CPT)

A Control Power Transformer (CPT) is used to convert one voltage (typically incoming power) to another (typically control power). Our application has an incoming voltage of 480VAC; we will need 120VAC in the panel for our Power Supply, and 120VAC service outlet.

To size the transformer, determine the total load (in VA) of all de-vices that are 120 VAC powered (the secondary voltage of the CPT).

1.4A x 120V (Power Supply) + 1.5A x 120V (Typical Laptop power supply) = 348VA

Select a 500VA Transformer

Part Number: MT0500A

CPT Primary Fuse Block

The Primary Fuse Block allows for the use of fuses to protect the transformer from overcurrent.

Part Number: KCCFPX2R

CPT Primary Fuses

Select the Primary Fuses (Qty 2) using the sizing tables from the “Control Power Transformer (CPT) Fuse Selection Guide”. Use the Power Circuit table since our application is a power circuit.

Select the primary fuses using the sizing tables. Find the intersec-tion of the selected transformer VA rating (500) and the primary voltage (480 VAC). The required fuse is 3A

Part Number: ATDR3

CPT Secondary Fuses

Secondary fuses prevent the devices connected to the transform-er from receiving too much current.

Select the secondary fuse using the sizing tables. Find the inter-section of the selected transformer VA rating (500) and the sec-ondary voltage (120 VAC). The required fuse is 6.25 (pick 8A – next available size in selection table)

Part Number: ATDR8


Main Circuit Breaker

The main circuit breaker provides overcurrent protection to the entire panel based on the total current consumption of the entire circuit, by preventing the wires in the panel from conducting more current than they are rated for. All power to the panel can also be turned off via the main circuit breaker.

The main breaker also protects the panel from a short circuit (which can generate MUCH more current than a typical overcurrent situation).

Select the main circuit breaker based on 1.) Short Circuit Interrupt Rating (determined by the main electrical power from the utility company) 2.) Total Current Consumption of devices using 480 VAC multiplied by a factor of 150%

Total Current Consumption = CPT Input Current (.6 A – Calculated using the formula I=(500 VA)/(√3 ×480 VAC)) X 150%
= .9A
Select a 15 A circuit breaker.

Part Number: 3VA51954EC310AA0

Main Circuit Breaker Lugs

Lugs are used to physically connect the wire to the line and load side of the circuit breaker terminals.

Size lugs based on the compatible frame size of the transformer.

Select Qty 2 compatible with 3VA51 circuit breaker frame

Part Number: 2 x 3VA91330JB11

Main Circuit Breaker Handle

A circuit breaker handle allows for manual control of a circuit breaker from outside the enclosure.

Select a circuit breaker handle based on type (Rotary Through the Door) and Compatible Breaker Frame (3VA51).

Verify that the NEMA rating fits our outdoor application (NEMA 3R)

Part Number: 3VA91370FK31


Terminal Blocks and Accessories

Terminal blocks allow for easy wiring and distribution of power and signals throughout the panel.

Select feed through terminal blocks and ground terminal blocks based on wire gauge to be used (18AWG for 120VAC circuit) – UT 2.5, and UT 2.5 PE

Feed Through Block Part Number: 3044076

Ground Block Part Number: 3044092

Select fused terminal blocks for Analog I/O.

Part Number: 3046032

End covers electrically isolate groups of terminal blocks. Select based on compatible blocks (UT 2.5)

Part Number: 3047028

Partition plates visually isolation groups of terminal blocks. Select based on compatible blocks (UT 2.5)

Part Number: 3047167

Plug in bridges jumper groups of blocks together for distribution of the same voltage to multiple devices. Select based on compatible blocks (UT 2.5) and number of positions (10) – Note that these can be cut to desired number of positions.

Part Number: 3030271

End Clamps prevent components from sliding on DIN Rail. Select 1 for each end of DIN Rail

Part Number: 0800886


DIN Rail

DIN Rail is used to mount components inside an enclosure.

Select the AWC recommended DIN Rail.

Part Number: 1201730


Wireway

Wireway allows for routing of wire inside the enclosure in a neat manner.

Select wireway based on dimensions that allow required wire amount to fix, and desired color.


Part Number: 3240199

Wire

Wire is sized based on current capacity.

We will typically use different wire colors based on the circuit.

Size the wire for the main 480 VAC circuit based on the chosen main circuit breaker (15A) using the “Wire Size and Selection Criteria” blog post – 14 AWG wire

Select colors using selection criteria:

480VAC Phase 1,2,3 – Brown + Orange + Yellow
480VAC Neutral – Grey
480 VAC Ground – Green

Part Number: WITHHN14STRBRW, WITHHN14STRORN, WITHHN14STRYEL, WITHHN14STRGRY, WITHHN14STRGRN

Size and select the 120 VAC circuit wiring the same way (based on the total output current of the CPT – 0.6 A):

16 AWG – MTW (based on its recommended use inside panels)

120VAC Hot – Black
120VAC Neutral – White
120VAC Ground – Green

Part Number: WIMTW16STRBLK, WIMTW16STRWHT, WIMTW16STRGRN

Size and select 24VDC circuit wiring the same way (based on total output current of the Power Supply – 3A.

24 VDC+: – Red
24 VDC-: – Black

Part Number: WIMTW20STRRED500, WIMTW20STRBLK500


Enclosure

Select an enclosure with an indoor NEMA rating (1 minimum) that fill allow for all components to fit with ample space for airflow and wiring.

Part Number: WM303008NC

Nitin Patel is an Automation Specialist for AWC, Inc. in the Dallas, TX office. He is a Certified Siemens Technology Specialist for Factory Automation. With over 14 years of experience in industrial automation, he has a BS in Electrical Engineering from Texas A&M University.

Nitin Patel

Product Specialist

Nitin Patel

Product Specialist

Nitin Patel is an Automation Specialist for AWC, Inc. in the Dallas, TX office. He is a Certified Siemens Technology Specialist for Factory Automation. With over 14 years of experience in industrial automation, he has a BS in Electrical Engineering from Texas A&M University.
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