Read a solar pump inverter nameplate and datasheet as a matching exercise, not as a shopping list. The nameplate tells you what the exact unit in front of you is rated for; the datasheet tells you the limits that unit must stay inside. If the pump nameplate, the PV module datasheet and the inverter nameplate do not agree on voltage, phase and current, the system is not ready to order — however close the kilowatt figures look.
Start with the pump, then check the inverter against it. For the selection logic that sits behind this check, see How to Choose a Solar Pump Inverter: 7 Key Factors. For what happens after the match is confirmed, see How Do I Wire a Solar Pump Inverter to Panels and a Pump?
What Each Nameplate Field Means
Rated power (kW). This is the motor power the drive is built to serve, not a promise that any pump of that power will work. A 7.5 kW drive and a 7.5 kW pump can still be incompatible if their voltage or phase differ, or if the pump full-load current is above the drive output current.
Input voltage and PV input class. On a solar pump inverter this is a DC range, for example DC 180–450V or DC 250–900V. The lower figure is the floor the working string voltage must clear; the upper figure is the ceiling the string open-circuit voltage must never cross, including on a cold morning.
Output voltage and phase. This is what the pump actually receives. Single-phase 220V, three-phase 220V and three-phase 380–400V are different outputs, and a pump must match the output exactly. Phase cannot be fixed by choosing a larger kilowatt rating.
Current (A). Rated output current is the hard electrical limit. If the pump full-load current is above it, the drive is undersized even when the kilowatt labels match. Always compare current, not kW alone.
MPPT window. The maximum-power-point tracking window is the voltage band in which the drive can actually track the array at useful power. A string that sits inside the absolute PV input maximum but below the MPPT floor will start late and stop on cloud, because the drive has no working voltage to track.
Protection rating and enclosure. The protection class tells you where the unit may be installed and what it is protected against, such as dust and water ingress. Do not assume a standard housing suits an exposed outdoor site: check the exact model enclosure, and confirm whether a cabinet version is an option for that model.
Nameplate and Datasheet Fields at a Glance
| Field | What it means | What to check |
|---|---|---|
| Model and branch code | The exact variant, including voltage class and phase | Match the code to the datasheet row, not to the product family |
| Rated power (kW) | Motor power the drive is built to serve | Compare with pump rated power and full-load current |
| PV input class (DC V) | Allowed string voltage range | String Vmp above the floor; cold-morning Voc below the ceiling |
| Output voltage and phase | Voltage and phase delivered to the pump | Must equal the pump nameplate exactly |
| Output current (A) | Maximum continuous output current | Must cover the pump full-load current |
| MPPT efficiency | How closely tracking follows the array maximum-power point | Use only the figure published for the exact model |
| Protection and enclosure | Installation environment the unit is built for | Confirm the enclosure for the actual site, not the brochure |
Verified Example: QB100-PV Branches
The table below uses only figures published on the QB100-PV Solar Pump Inverter White Plastic Shell 0.4–37kW product page. The page also states MPPT tracking efficiency up to 99%, PV overvoltage, overcurrent and over-temperature derating, and that GPRS monitoring and IP54 cabinet versions are listed as options. Do not copy these branches to another product family.
| QB100-PV branch example | Pump power | Output | PV input class |
|---|---|---|---|
| QB100-0R7G-SS2-PV | 0.75 kW | Single-phase 220V | DC 180–450V |
| QB100-2R2G-S2-PV | 2.2 kW | Three-phase 220V | DC 180–450V |
| QB100-7R5G-4-PV | 7.5 kW | Three-phase 380–400V | DC 250–900V |
| QB100-037G-4-PV | 37 kW | Three-phase 380–400V | DC 250–900V |
Notice the pattern: the voltage class, not the kilowatt figure, decides the PV window. A 2.2 kW pump on a 220V branch and a 7.5 kW pump on a 400V branch need completely different string designs, even though both are ordinary farm pumps.
How to Read a Nameplate and Datasheet, Step by Step
- Photograph both nameplates. Record the pump nameplate (power, voltage, phase, full-load current) and the inverter nameplate (model code, output voltage and phase, PV input class) before any calculation.
- Match voltage and phase first. Reject any combination where output voltage or phase differs from the pump, whatever the kilowatt figures say.
- Check current, not just kW. Confirm the pump full-load current sits within the drive output current for the exact model.
- Find the exact datasheet row. Use the model code to locate the branch row. Family-level figures are not a substitute for the branch row.
- Test the string against both edges. Confirm the string working voltage clears the PV input floor and the cold-morning open-circuit voltage stays below the ceiling.
- Check the MPPT window separately. Confirm the string will work inside the tracking band in weak light, not only at midday.
- Confirm protection and enclosure for the site. Check the protection functions and the enclosure against dust, water, heat and mounting conditions at the actual site.
- Record every mismatch and stop. If any field disagrees, change the model, the string or the pump — do not average the figures or hope the drive will compensate.
Common Reading Mistakes
The most expensive mistake is reading only the largest number on the plate. A bigger kilowatt rating does not fix a voltage or phase mismatch, does not raise the MPPT floor, and does not turn a single-phase output into a three-phase one. A second common mistake is treating the PV input maximum as the working window: a string designed only to stay below the ceiling can still fail to start in the morning. A third is copying a figure from a different branch or product family because the model names look alike. Branch codes exist precisely because those figures differ.
Frequently Asked Questions
Is a bigger nameplate kW always better?
No — this is the trap. A larger drive does not correct a voltage or phase mismatch, does not change the PV input window for the branch you bought, and can make low-speed control and protection matching worse. Size from the pump current, voltage and phase first, then apply a modest margin for starting current and site conditions.
What if the nameplate and the datasheet disagree?
Trust neither until the conflict is resolved. Stop, confirm the exact model code on the unit, and ask the supplier to confirm the branch row in writing. A datasheet for the product family is not evidence for the unit in front of you.
Can I use panel Voc alone to design the string?
No. Voc checks only the ceiling. You also need Vmp to check the floor and the MPPT window: the string must work, not merely survive, at the lowest voltage it will see in service.
Does MPPT efficiency replace the voltage window check?
No. Efficiency describes how well the drive tracks once it has a usable voltage. It cannot create a usable voltage from a string that sits below the MPPT floor.
Is the protection rating the same as the protection functions?
No. The enclosure rating describes the housing against dust and water. The protection functions — such as PV overvoltage, overcurrent and over-temperature derating — describe what the drive does when conditions go wrong. Check both, separately, for the exact model.
If any field on your pump nameplate, module datasheet or inverter nameplate does not line up, send all three documents to IDEEI before ordering so the branch and string can be checked together.