ESSENTIAL INFORMATION & SUGGESTION
- Position of voltage at Site. if single phase then stability of neutral.
- Starter conditions and proper relay tripping.
- Real yield of water in bore well or open well.
- Maximum lower level of water in the well.
- Real requirements of water as per customer need.
- Whether there is problem of sand in bore-well / open well.
- Actual irrigation area of land.
The levels of head and discharge given in the performance / price list are according to the ideal conditions during testing. Practically the head and discharge may be less than given in the performance due to following reasons.
1) Frequency loss : if the frequency (HZ) is than 50 I.e. if it is 48, 49 than the speed decreases by 60 R.P.M. at loss of 1 freq.
2) Voltage loss : Result obtained is less due to less voltage.
3) Delivery pipe loss : if the delivery pipe found smaller & rough then pipe loss may occurs which result in reduction of discharge.
4) if the cable joints are not perfectly waterproof then the result may decrease.
(Change in result due to change in voltage)
| Volt after set gets Started. | Three Phase | Single Phase | |||
|---|---|---|---|---|---|
| Three Phase Volt | Single Phase Volt | Reduction Head (%) | Reduction of Dis (%) | Reduction Head (%) | Reduction of Dis (%) |
| 415 V | 415 V | NIL | NIL | NIL | NIL |
| 350 V | 350 V | 5 | 5 | 5 | 3 |
| 310 V | 310 V | 10 | 8 | 8 | 6 |
| 275 V | 275 V | 15 | 12 | 12 | 9 |
| 240 V | 240 V | 20 | 15 | 16 | 12 |
(Change in result due to change in Frequency)
| Frequency (Hz) | Change in Output | Change in Total Output (%) | |
|---|---|---|---|
| Head (%) | Dis (%) | ||
| 51 | +4 | +2 | +6 |
| Std. 50 | Std. | Std. | Nil |
| 49.5 | -2 | -1 | -3 |
| 49.0 | -4 | -2 | -6 |
| 48.5 | -6 | -3 | -9 |
| 48.0 | -8 | -4 | -12 |
| 47.5 | -10 | -5 | -15 |
- The following practically steps must be taken, when 3 phase voltages are less than 250V in V-6 pumps sets.
- Winding design from 3 H.P. to 7.5 H.P. is star connected. if the 3 phase voltages are less than 250 V, than the motor must be made double cabled and connections must be changed to star-delta and motor must be operated in delta. Or using a heavy single cable, the motor must be delta connected and operated in delta.
- if the 3 phase power is less than 250 V for 10 H.P. to 15 H.P. range then consumers are requested to current, minimum voltage drop may occur.
- if the power obtained is less on single phase, then the supply cable must be of good quality and must be used oversize with that, according to the performance table / booklet, the MFD of run capacitors must be increased.
Selection conclusion The net actual head after all deduction of losses (Pipe loss, Voltage loss, Frequency loss) from duty point head should be 10% higher than the required head at site.
