A Variable Speed Drive (VSD) is the modern answer to motor starting and control.
A VSD allows a standard electric motor to run at a variety of speeds and to self-adjust, as it is running.
This has huge advantages over conventional DOL (Direct On Line) starters which run only at a fixed speed and are relatively power hungry as a result.
Fitting VSDs to a new pumping system from the start lets you select more efficient pumps and a wide range of duties. A single large pump could be used to run several Centre Pivots at once (at full speed) or just one pivot (with the pump running slowly), this means fewer pumps, simpler management and lower power consumption.
Fitting VSDs to existing motors saves power (Inherent 10% power saving over DOL setups), allows for automation, reduced labor costs and reduced power wastage due to over pumping.
What are the latest Irrigation advances with VSD's?
In line booster pump stations, do away with unnecessary (and expensive) holding dams
Block irrigation (Micro & Drip) can be very finely managed and are more efficient with pressure set point control
What are the advantages of fitting VSDs?
- Better, more efficient pump selection
- Accurate pressure management – consistent pressures without over pumping
- Extensive automation options - Remote startup
- Auto restart after power cut
- Cell-phone control and monitoring
- Slow speed pump start up
- Eliminates water hammer
- Reduced wear and tear on pump and motor
- Auto motor limiting – Overload and motor burnout protection
- Pressure control – pipe line burst safety
- “Run-dry” protection on pumps
Power factor correction
- Inherent in VSD technology is power factor correction of better than 0.93 with no capacitors.
Are there any negatives to having a VSD?
- Expense – but with a short payback period - Predicted power price increases will further shorten payback
- Complex technology – tried and tested in Zambia (for a long time in other industries) – good back up in Zambia.
- Sensitive to power surge – Drop out fuses and protection must be installed.
- These protect from fluctuating voltage and power quality and are a worthwhile addition to any system, even those without VSDs