How to configure a solar (AC) pump system?

Cactus1549

First, the voltage of solar is directly connected to the DC bus of the inverter. In order to make the motor obtain enough voltage, the voltage on the DC bus must be greater than √ 2 times of the motor voltage. This voltage relationship is determined by the characteristics of rectifier circuit and inverter circuit.

At the same time, the open circuit voltage of the photovoltaic panel shall not exceed the maximum voltage that the inverter can carry, generally 800V.Otherwise, the inverter may be damaged.

Then there is the power relationship between the motor and the solar panel. The power of the solar panel, such as 410W, refers to the measured power of 410W under the STC test conditions.

But it is difficult for the natural sunshine to reach the STC intensity. Moreover, the fixed solar panels are slanted in the morning and afternoon, which further affects the power of the solar panels.

Therefore, in order to obtain sufficient power for the motor, we will amplify a factor by referring to the power of the solar panel under STC conditions. We recommend 1.6 - 2.2times.

Especially for pumps with high lift, it is necessary to increase the amplification factor. Otherwise, if the water pump cannot work at full power, it will be difficult to discharge water.

Cactus1549

configuration-list-for-ac-pump.pdf

238kB

Cactus1549

confirmation-form-for-ac-solar-pump.xlsx

10kB

Cactus1549

Alternatively, you can also provide us with your requirements and on-site conditions and we will make the solutions for you.

requirements-analysis-form0.docx

380kB

SolarLucy

Hello,have a solar water pump project in Africa
it have 1000meters distance between solar system and well.The depth of the well is 200-250meters.
We worry about the voltage drop problem,how to design suitable solar water pump system?
We plan to use 15hp water pump,the rated head is 200meters rated water flow is 10m3/hr
Water pump will use 380VAC power source.
It will use 30pcs 580W solar panel which have 51.4V open circuit voltage,43.22V max power voltage,13.42A max power current,14.22A short circuit current

Cactus1549

SolarLucy
We noticed that the main problem of this project is that the cable is too long.
First, we should make the VFD as close to the water pump as possible, that is, near the wellhead, but it will still be more than 250m away from the water pump, so a sine filter needs to be added.
Then, we need to analyze the voltage drop of each section of the line, which is crucial for the normal operation of the equipment.
For an 11kW motor, the current on both the AC and DC sides is about 20A.
After calculation and selection, we found that it is more appropriate to use 10mm² copper wire from the combiner box to the VFD and from the VFD to the water pump.

First, let's first we check the motor cable
The resistance of a 250m cable is R2 = 0.4375Ω
The voltage drop per phase is ΔU2 = I * R2 = 8.75V
The total heat generated by the cable is Q2 = 3 * I² * R2 = 525W

Then, check the DC cable
The resistance of a 1000m cable is R1 = 1.75Ω
The voltage drop per phase is ΔU1 = I * R1 = 35V
The total heat generated by the cable is Q2=2 * I² * R1 = 1400W

The voltages of 15 or 14 series PV strings are 648.3V/605.08V. After deducting the voltage drop of 35V, it can still meet the normal operation of the VFD and the water pump.
Finally, considering the loss of about 2kW on the wire, 30 solar panels (17.4kWp) may not enough for the normal operation of the water pump. It is recommended to use 42 panels, 14 series and 3 parallel.