Choosing a design mode
The four startup cards — fixed tilt or tracker, string or central inverter — what each means and what each changes in the interface.
Every launch begins with two questions: how the modules are mounted, and how the plant is wired. The answers are offered as four cards before the main window opens, and one of them must be chosen to get any further.
- What it shows
- The full startup dialog: the title, the two column headers (Fixed Tilt, Single Axis Tracker) and all four cards with their Select buttons.
- How to get there
- Launch the app. The dialog is the first thing shown, before the main window.
The choice is not a preference you can revise later. It decides which input groups exist, how units are placed on the ground, what equipment is counted, and what the summary columns are called. It cannot be changed for a session already in progress — to work in a different mode you move to a new session, which the next-to-last section covers.
The four combinations
| Mounting | Electrical | Chain shown on the card |
|---|---|---|
| Fixed Tilt | String Inverter | Modules → MMS-Table → String Inverter → ICR |
| Fixed Tilt | Central Inverter | Modules → MMS-Table → SMB → Central Inverter |
| Single Axis Tracker | String Inverter | Modules → Tracker MMS → String Inverter → ICR |
| Single Axis Tracker | Central Inverter | Modules → Tracker MMS → SMB → Central Inverter |
The chain on each card is the equipment path from module to grid connection. MMS is the module mounting structure; SMB is the string monitoring box; ICR is the inverter control room building.
Fixed tilt or single axis tracker
This is a decision about the structure, and it is the one that changes the plant's geometry.
Fixed Tilt. Modules sit at one angle on static racks, facing the equator — south in the northern hemisphere, north in the southern. Rows run east to west and repeat northward at a row pitch. The tilt and the pitch are derived from the site latitude unless you override them, and the pitch is what keeps one row from shading the row behind it in midwinter.
Single Axis Tracker. Modules are carried on a horizontal, north–south axis and rotate about it through the day, so the panels sweep from facing east in the morning to facing west in the afternoon. There is no fixed tilt to set: what you set instead is the rotation limit the structure allows. Tracker units are long in the north–south direction and repeat eastward at an east–west pitch.
- What it shows
- The plot area after a tracker run on the same site, so the north-south unit orientation contrasts with the fixed-tilt image.
- How to get there
- Single Axis Tracker + String Inverter on the same file used for the fixed-tilt image. Fit the view.
- Callouts to add
- Add a north arrow and label the tracker axis direction.
The two mountings are configured through different groups in the input panel:
Two groups: MMS-Table Configuration and Spacing & Tilt.
| Field | Default | Unit |
|---|---|---|
| Orientation | Portrait | — |
| Modules per row | 28 | — |
| Rows per MMS-Table | 2 | — |
| Gap between modules E-W | 0.020 | m |
| Gap between modules N-S | 0.020 | m |
| Gap between MMS-Tables | 1.0 | m |
| Override tilt angle | off — derived from latitude | — |
| Override row pitch | off — derived | — |
With portrait orientation the module's short side runs east–west and its long side north–south; landscape reverses that. See Table configuration and Spacing and tilt.
String inverter or central inverter
This is a decision about the electrical topology, and it changes what is counted and how cables are run rather than where units sit on the ground.
Many string inverters are distributed across the plant, sited in the gap bands between rows, from clusters of the tables they serve. Each is drawn as a small marker on the plot.
Cabling has two legs:
- DC string cables, table to inverter, counted twice over for the positive and negative conductors.
- AC cables, inverter to the nearest control room, counted once as a three-phase run and routed on right angles only — horizontal and vertical segments, never diagonals.
Max strings per inverter governs how many strings one inverter accepts, which in turn sets how many inverters the plant needs. One string is one row of modules within an MMS-table.
Both topologies then carry medium-voltage cables from each control room to the main control room, over a shared trunk rather than parallel runs. See Cable routing.
What changes in the interface
The mode does not hide optional extras. It decides which input groups are built at all, how several labels and column headings read, and how a few pieces of equipment are placed.
Mounting
| In the interface | Fixed Tilt | Single Axis Tracker |
|---|---|---|
| Input groups | MMS-Table Configuration and Spacing & Tilt | Both replaced by a single Tracker Configuration group |
| Unit count columns | Full Tbl and Half Tbl | Full Trk and Half Trk |
| Angle column | Tilt(°), with a trailing * when auto-calculated | MaxAng(°) |
| Lightning arrester footprint | A 30 m by 7 m rectangle; tables overlapping it are removed | A 1 m by 1 m pole marker, snapped into the nearest gap between tracker columns, so no tracker units are removed |
| Cleaning robot lines | Run west to east | Run north to south |
Electrical
| In the interface | String Inverter | Central Inverter |
|---|---|---|
| Group title | String Inverter | SMB – String Monitoring Box |
| Strings field | Max strings per inverter | Max strings per SMB |
| Extra field | — | Max SMB per Central Inverter |
| Equipment columns | Str.Inv · Inv kWp | SMBs · SMB kWp · C.Inv · CInv kWp |
| Cable columns | StrDC(m) · AC-ICR(m) | StrDC(m) · DC-CInv(m) |
| Loss row labels | String DC cable losses, AC cable losses (Str. Inv. → ICR) | The same rows read MMS → SMB and SMB → Central Inv. |
| Efficiency row | String Inverter efficiency | Central Inverter efficiency |
| CAD export layer | INVERTERS | The same layer, named for the monitoring boxes |
| Auto-built diagram | PV → String Inverter → ACCB → Transformer → MV Panel → Grid | PV → SMB → Central Inverter → Transformer → MV Panel → Grid |
| Maximum practical DC/AC ratio offered when sizing from an AC capacity | 1.5× | 1.4× |
The full column list, in order, is in Summary columns.
Moving to a different mode
The mode belongs to the session. File ▸ Move to String / Central Window… (Ctrl+N), also on the toolbar as ⊕ Move to String / Central Window, presents the choice again. Two things about it the label understates:
- It switches the mounting type as well. What opens is the same four cards you chose from at launch, so the new session can be fixed tilt where the one you came from was a tracker plant. The name reads as though only the inverter topology were on offer; the choice is the full four.
- It opens a new, independent window. The session you came from stays open beside it. This is not a mode switch applied to the work in progress, which is why two design modes can be held on screen at once and read against each other.
The new window does not inherit the work in progress. Its boundary file and its inputs are entered again there, and the layout, hand edits, diagram and materials list of the session you came from stay with that session. Save each one with File ▸ Save Project… to its own project file.
Comparing two topologies on the same site is therefore two sessions and two project files, not one session switched back and forth — but both windows can be open together. Load the same boundary file in each, leave the shared inputs identical, and compare the summary rows.
Where to go next
Your first layout
A complete run in fixed tilt with string inverters
Tracker configuration
Every tracker field, its default and what it drives
Inverters and monitoring boxes
Strings per unit, inverter files, and turning cable calculation on
Saving and reopening projects
What a project file keeps, and why a mode change means a new session