HOW TO BUILD ATS PANELS
A STEP-BY-STEP TUTORIAL ON HOW TO BUILD ATS PANELS
SKIP ATS PRESENTATION BRING ME TO INSTRUCTIONS
ATS WORKING PRINCIPLE
ATS panels maintain power continuity in buildings in case of power outages. An ATS panel is one of the main components of a backup system. In specific details, it is an electrical cabinet that connects your building to the GENERATOR or the MAINS.
WHAT DOES MAINS MEAN?
The origin of this word is a little bit controversial. But, in common language, it means the public electricity distribution network. It is of British origin, and widely accepted. In the U.S. the correct term is UTILITY POWER. We examine a three-phase system with neutral with a nominal voltage in the range of 380 to 440Vac at 50 or 60Hz.
WHAT DOES AUTOMATIC MEAN?
Only when an ATS controller controls the transfer switch can we call it "automatic". In other words, it will automatically govern all functions by managing the connection assignment of the LOAD to MAINS or GENERATOR.
WHAT IS A TRANSFER SWITCH?
The TRANSFER SWITCH is the powerful hardware capable of connecting or disconnecting the MAINS, the GENERATOR and the LOAD. It allows the flow of the electric energy. It can interrupt the flow at any time upon a particular command. It is the heaviest component of the ATS panel especially when the power exceeds 100kVA. There are two basic transfer switch types: made with CONTACTORS or MOTORIZED CHANGEOVER
UNDERSTANDING CHANGEOVER SWITCH PANELS
CONTACTORS VERSUS MOTORIZED CHANGEOVER
The CONTACTORS, usually four-pole, are coil-operated switches that close a circuit. The "interlock" mechanism prevents combined activation. Only one contactor, GENERATOR or MAINS, must be active. An electrical interlock adds an extra layer of security. To put it another way, the two coils cannot be supplied together when the auxiliary normally closed and open contacts are connected in series. The ATS controller adds delays in favour of a safe switching of the CONTACTORS from GENERATOR to LOAD and vice versa.
IN THE PICTURE CONTACTORS WITH AUXILIARY CONTACTS
THE TERMINALS "A1" ARE CONNECTED TO THE NEUTRAL. THE TERMINALS "4" AND "8" ARE CONNECTED TO THE ATS RELAY BOARD
The CONTACTORS used in the ATS business are supplied with alternating 230V. The drawback is that an unstable voltage source can limit the performance of the transfer switch system.
AC COILS
In this instance, the generator connects the LOAD to the GENERATOR. In the event of a short circuit or persistent overload, the coil's voltage will drop noticeably. The contactor loses mechanical energy and the contacts start opening. This is a dangerous situation that can create sparks. You can expect damage to the contacts. In the worst case, the contacts open, the voltage rises immediately and the contacts close again. A dangerous "MACHINE-GUN" phenomenon will take place.
DC COILS
A DC-coil-driven contactor may perform much better. Versions with DC coils are expensive and used only in particular cases. Assuming you provide a stable DC voltage, for example, using a backup battery, you can make a quasi-perfect contactor-based transfer switch system.
ENERGY CONSUMPTION
Therefore, the coil must always be supplied to keep the contactor closed. The average consumption is 10 Watts per small contactor but reaches 20 watts for large contactors. Supposing a 24-hour standby system, you have to check for the bill after one year.
CONTACTORS COILS LIFE
The life of the coils, supposing a 24h duty, is expected to be several years. When a coil fails, you must replace the coil. In the meantime, without a manual bypass switch, you have no electricity. The price of AC contactors is reasonable up to a power of 80KVA. The great advantage of ATS panels with contactors, is the ability to protect the LOAD very well. They can therefore intervene in switching from MAINS to GENERATOR following complex settings of timers and priority thresholds.
THE MOTORIZED CHANGEOVER
Over 80KVA, it is better to use a motorized transfer switch. The motorized transfer switch is complex from the mechanical point of view but it can offer switching currents over 2000 A. Big systems feature a combination of contactors and motorized transfer switches. A typical configuration consists of one master panel capable of switching big currents. Then, several panels with relatively small contactor-based transfer switches serve the small LOADs. To get the most from a motorized transfer switch a good electronic board is required.
ATS PANELS BASIC FEATURES
ATS CONTROLLER INSTALLATION MANUAL
All parameters, alarms, and additional functions are indicated using a display capable of operating in a wide range of temperatures. The ATS panel must display all electrical parameters of the MAINS, GENERATOR and LOAD. If the ATS panel is committed to directly controlling the engine, it should provide all basic instruments. The ATS panels, finally, must be capable of protecting the LOAD and GENERATOR from all kinds of issues. It must comply with international standards, in particular, NFPA110, IEC 61439 (-1-2-34-5-6-7), IEC 60529, and CAN/CSAC282-M89. The panel must be delivered with schematics, a components list, quality certification, and an instruction manual for use and maintenance.
ATS PANEL AND ELECTRICAL NOISE
It is essential to shield the ATS panel electronic parts from electrical noise. For this reason, the enclosure of the electronic parts must be made of metallic material. The best solution is a ferrous-based metal like steel. The 32-bit processor, the core of the ATS panel, runs into a very well-protected Faraday shelter. The rear cover made of metal is the best solution for shock-proof equipment. This gives an extraordinary advantage over competitors' plastic-based enclosures. The smartest idea is to use the frontal metallic door of the panel. This is the way the Be242 works. The door protects the CPU, which is also insensitive to noise produced when contactors or a motorized transfer switch switch the LOAD.
INSIDE A TYPICAL ATS PANEL OVERVIEW
[1] BATTERY CHARGER [2] INTERFACE BOARD [3] ATS CONTROLLER [4] CONTACTORS [5] CURRENT TRANSFORMERS [6] CABINET DOOR [7] [8] CIRCUIT BREAKERS [9] [10] POWER TERMINAL BLOCK
A WIRING DIAGRAM OVERVIEW
The ATS controller governs the system and transfers the LOAD to the GENERATOR or MAINS smoothly and with short downtime. The ATS panel wiring diagram illustrates the internal connections.
OPEN THE WIRING DIAGRAM PAGE; CLICK ON THE IMAGE
BUILDING ATS PANELS THE ULTIMATE GUIDE FOR BEGINNERS
BEFORE COMMENCING YOUR WORK
Before commencing you must do all mechanical work about drilling the back-plane.
This is a crucial job. We recommend that you prepare precise footprints of the holes. After using finishing tools like iron files carefully remove any remains. Various dirty remains can compromise the panel's long-term reliability. Power contactors and motorized switches must work in clean spaces. Iron filings and iron shavings are particularly dangerous for electronic boards. They can make short circuits in the long term. At the end of the work use a magnet to remove all remains. Avoid the use of compressed air. It could be dangerous for your skin and eyes. When making mechanical work follow safety rules. Protecting the holes with a special anti-rust paint may prolong the life of the mechanical items. Use nut lock glue where possible.
INSTALLING THE INTERFACE BOARD
The Be242 ATS controller features the Be242RB interface board. This is a key component of the ATS panel. The main advantage consists in drastically reducing the component count in your panel.
One of the main tasks of the board is analog and digital signal acquisition. It includes all DC relays to control the engine and the AC relays committed to drive the contactors or the changeover. All relays are fuse-protected. To fix this board in the panel you have to install a standard DIN rail. Two clips will hold the board in a stable position. The metal cover shields electromagnetic noise generated by the changeover.
WIRING THE CIRCUIT BREAKERS
Connect Phases L1-L2-L3-N from the ‘GENERATOR’ terminal block to the entrance of the circuit breaker on the left side.
Connect the R-S-T-N terminal blocks in the same way. Use a 1,5 square mm flexible stranded copper cable. See the above picture.
VOLTAGE MEASUREMENT CONNECTIONS
With this task, you will connect the voltage measurement circuits. You can see in RED colour the three cables for the GENERATOR voltage measurements (5-6-7).
The three YELLOW cables provide voltage measurements of MAINS (mains) (1-2-3). We recommend to use 1,5 square mm flexible stranded copper cable.
BATTERY CHARGER AND CURRENT TRANSFORMER
With this task, you will connect the current transformers to the BE242RB inputs. The end side of the common cable must be grounded. Connect the phase ‘2’ and neutral ‘4’ to supply the battery charger.
We recommend using a 1,5 square mm flexible stranded copper cable.
WIRING THE GC COIL
Connect the A1 & A2 terminals of the GC coil.
Connect the neutral from the AGCB and connect the KG output of the BE242 relay board through the auxiliary contacts.
WIRING THE MC COIL
Connect the A1 & A2 terminals of the MC coil.
Connect the neutral from the AMCB and connect the KM output of the BE242 relay board through the auxiliary contacts.
WIRING THE CONTACTORS
This is the most critical part of the job. Particular skills are required to connect big-size wires. You have to follow the recommendations and instructions of the contactor manufacturer. This will avoid overheating the connection points. Apply the recommended force to guarantee good contact especially when high currents are involved. Connect phases ‘L1’-’L2’-’L3’-‘N’,connect phases ‘R’-‘S’-‘T’-‘N’
As a reference, a 60kVA panel require a 25 sqmm size. This size will allow a continuous current of about 100 amps. For terminal blocks, the better choice is to use a 35 sqmm size.
WIRING THE CONTACTORS OUTPUT
This is the most critical part of the job. Particular skills are required in connecting wires of big size. You have to follow the recommendations and instructions of the contactor manufacturer. This will avoid connections overheating. Currents over 100 Amps may circulate in these wires.
Use the recommended force to guarantee good contacts. Connect phases ‘L1’-’L2’-’L3’-‘N’ together with the phases ‘R’-‘S’-‘T’-‘N’ Each output phase must enter the proper current transformer before connecting the terminal blocks. The neutral wire must be directly connected to the terminal block.
DRILLING THE FRONT DOOR OF THE CABINET
The main advantage of using the BE242 controller is time-saving. The BE242 is a square-shaped ATS controller that needs a round hole. This means that you can make the hole using a circular saw. You are required to download the template. Double-check the dimensions reported on the drawing. This is particularly important if you are not sure about the printing precision. Choose the correct position for the template [1] over the panel [5]. Use a paper tape to fix and hold the template. Make a round hole between 56mm to 64mm. This will be the main hole for the BE242 controller.
Make four holes [3] of about 4,5mm. These holes will allow you to fix the controller on the panel by using 4 nuts 4MA. You can additionally make a 22mm hole [4] if you need to install an emergency stop button. See the picture.
INSTALLING THE ATS CONTROLLER ON THE DOOR
The Be242 requires only 4 small holes and a circular hole for the ATS cable (supplied in the KIT). The polypropylene gasket will provide an IP54. If the case wires the emergency stop pushbutton to the back of the ATS controller.
VERY WELL DONE!
CONNECT THE ATS CABLE TO THE ATS CONTROLLER ON ONE SIDE. CONNECT THE OTHER SIDE TO THE RELAY BOARD.
YOU DID A GREAT JOB
ATS PANELS: THE CHECK-LIST
Very well done. You are supposed to finish your panel. Your work is not over yet. We recommend that you print the following checklist. Examine each item thoroughly, step by step. This is a general guide. You can integrate it based on your experience.
THE FINAL CHECK BEFORE TESTING
1) The controller is very well fixed on the front door. Make sure the nuts are tight. The surface of the panel is clean.
2) Make sure the panel structure and grounding nuts on the front door are tight.
3) The backplane that supports the hardware is normally held in place by 4 bolts M6. Make sure you have a spacer between it and the panel frame. Being the bolts soldered, if you apply too much force, without a washer spacer, you can de-solder the bolts.
4) Verify that all screws of the terminal blocks, fuse holders, CTs, circuit breakers, and auxiliary contacts are properly tight.
5) Verify that there are no strands exposed on each cable termination. You could get arcing or overheating.
6) Check if the bolts, or screws, on the contactors, are tight according to the contactor specifications.
7) When using multipolar connectors (in this case the ATS cable) check the holding screws: must be tight.
8) The emergency switch on the front door must be carefully verified. If necessary use thread locker adhesive to avoid rotation of the switch.
9) Verify the size of the fuses (if the case). Put a proper label indicating the value. Add spare fuses for the user.
10) Check the free mechanical movement of the contactors. Check the mechanical interlock. You must not be able to activate both contactors. The mechanical interlock will allow only one contactor at a time.
11) Hold the panel in a vertical position. Hit gently the panel with a rubber mallet. Check for vibration and collect various dirty remains (iron filings, copper remains and so on) on the bottom of the panel. Use a powerful vacuum cleaner. Make sure there are no extra items (screws, loose terminals, tools, pieces of wire and so on). If you are not able to remove iron filings use a magnet.
12) Verify the presence of the labels indicating Mains, GENERATOR, LOAD, Phases, Electric Danger and so on.
13) Put inside the door an adhesive sheet that illustrates the schematics and the nominal panel data. This may help an electrician in case of service.
14) Mechanically check the closure of the door. If your panel is over IP42, check the gasket.
15) Make sure the ATS controller's settings match the size of the current transformers.
THE FINAL CHECK BEFORE TESTING
It is quite clear the test must be performed by qualified personnel only. Having said that before connecting any voltage, you must close the AGCB and AMCB circuit breakers. Check the following:
- the continuity of the connections with OHM-METER by following the schematics.
- for the polarity of the plus and minus.
-insulation between phases LI-L2-L3-N.
-insulation between phases R-N.
-resistance of the BATTERY CHARGER TRANSFORMER COIL between phases S and N.
-resistance of the MC COIL between phase T and N.
-insulation between the common ground of the panel and all connections (except the CTs).
-the continuity of the CTs to the ground.
Proceed with the electric test following the international safety rules.
(1) The contactors, when activated, should not emit noise. The presence of noise could be caused by iron filing pollution on the body of the contactors.
(2) Test the voltage drop between MAINS and LOAD with at least 10 Amps of load (R-U, S-V, T-W, N-N). It should be in the range of a few mV ac.
(3) Test the voltage drop between MAINS and LOAD with at least 10 Amps of load (L1-U, L2-V, TL3-W, N-N). It should be in the range of a few mV ac.
(4) Test all INPUT-OUTPUT connections of the engine and test the battery charger.
(5) Remove all connections after testing. Tight the bolt again without forgetting the washers (in case connections are directly made on the contactors or motorized changeover).
(6) Remember to put the spare panel fasteners in a small box or envelope. It will be important for the user.
(7) Close and open the panel door several times. Check for mechanical issues and the proper movement of the ATS cable.
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