Is it possible to start a motor with grid and then switch it to solar inverter?
I am planning to built a solar power plant for my 5HP 3 phase induction motor (415V, 7.9A) without using batteries.
1. So how much capacity of panels do I require to build it?
2. Some says starting current is high so you must install 12-13KW power plant. So in-order to decrease the project value, Can I start the motor using grid and after certain time period (say hardly 30sec) changing it to solar inverter?
3. If so, is there any equipment available in the market which changes automatically to grid after few sec?
4. Is there any alternative solution?
- roderick_youngLv 77 years agoFavorite Answer
This is a perfect case for grid-tied solar. Any grid-tied inverter does exactly what you want. It will use all the power it can from your solar array ("power plant"), and if it needs more, will draw exactly what it needs from the grid. As a bonus, if your solar is generating more than you use, you'll build up credit on your electric meter in most cases, that can be drawn down later when needed.
- GoneLv 67 years ago
Q1. The solar panel capacity will be determined by analysis the motor and load performance requirements compared to the variability of the solar energy received.
Q2. You can probably not safely switch the motor from grid operation to solar inverter operation.
Q3. There is probably no such equipment available.
Q4. If you use a motor control inverter (variable frequency drive, VFD) the motor can be started without drawing from the solar panels much more current than is required for normal motor operation. The VFD will not be suitable for powering anything but the motor. If the motor is 415 star, 240 delta, it would probably be better to use the delta connection. Even then you will need about 350 volts DC input from the solar panels. This is probably the least expensive approach if you can figure out how to do it properly.
- billrussell42Lv 77 years ago
You could use batteries or a supercapacitor to store the energy needed for the startup. Given that sun power is erratic, eg, a cloud could drift across the sun, decreasing output, you would need batteries anyway
You will need a huge solar panel to handle the power. Assuming PF of 0.8, that is
P = (415)(7.8)(√3)(0.8) = 4540 watts
Assuming a 90% efficient inverter, you need to generate 5050 watts.
Solar panel output is about 100-200 watts per square meter, depending on efficiency, which depends on cost, to some extent. Taking 200 watts per square meter
5050 watts / 200 watts / m² = 25 m², plus extra to charge up the batteries or supercap.
- fuzzyLv 67 years ago
starting current depends HUGELY on the load type. Using a modern VS inverter you can set them for a soft start provided the initial load isn't too great.
What the others say about panel size & grid tied is sound advice