The World's Largest Independent Producer of Alternators 1 - 5,000kVA
Applications / Irrigation

IRRIGATION

The Mecc Alte irrigation product has been developed from over 70 years of experience, in understanding the application requirements, advanced products with upgraded insulation systems help in maintaining application efficiencies and increasing reliability. When controlled levels of water is supplied at intervals these alternators are designed to maximise and drive the motors through the MAUX auxillary winding system, and the added insulation protection protects the alternator windings from ingress of moisture.

For this application our ECP28/ECP32 alternators are used in pivot and fixed systems, typically small belt-driven machines, normally 10kW to 30kW in power.

They are brushless, self-excited with electronic regulation using the formidable Mecc Alte DSR regulator. The system has the Mecc Alte trademark MAUX auxiliary winding to give outstanding motor start performances, starting motors with impact loads up to three times the size of the alternator (allowing up to 35% transient voltage excursion). With excellent MTBF (Mean Time Between Failure), the reliability is optimised without the need to worry about maintaining airgap on transformers, as with older, traditional machines.

PERFORMANCE INDICATORS

  • High transient power for economic alternator selection
  • Low reactance (x”d) values to enhance motor starting (8-11%)
  • Volts/Hz characteristic – underspeed protection (voltage reduces proportionate to the rpm to limit excitation current)
  • Overload protection (operational after 20 seconds to avoid tripping on motor starting)
  • TOTAL+ winding protection – a black flexible compound coating on main and exciter stators with EG43 compound on main rotor
  • ±1% voltage regulation through all steady state load conditions and inclusive of hot and cold variations
  • Voltage recovery to within 3% of set voltage within 0.2 seconds
  • Sustained >300% short circuit support for 20 seconds with preset cut-out period for safety
  • Voltage adjustable on the DSR regulator to satisfy a range -14% to +14%
  • 12 wire reconnectable to have more options on voltage – 1ph and 3ph
  • IP23 (splashproof to 60° from vertical)
  • Rugged construction able to withstand up to 5G in any direction

MAIN ROTOR AND STATOR

Impregnated using the latest trickle technology, the non-hygroscopic resin is added to the windings and then cured in the same process while rotating to ensure best coverage possible. The insulation materials used are Class H throughout. Copper used for the main windings is G2 with two layers of enamel; the winding for the MAUX is G4 with four layers. Add to this the upgrade option of TOTAL+ to have the rubber-like black flexible compound over the main and exciter stators, and EG43 compound over the main and exciter rotors, and you have a very high degree of protection against harmful article ingress.

BEARINGS

Sealed-for-life, premium quality ball bearings are used throughout with oversize bearings at the driven end to accept the side loading in belt-driven applications. Rear bearing is outboard of the exciter for easier examination of rectifier assembly.

EXCITATION SYSTEM

The brushless excitation system takes the DC voltage from the DSR regulator according to load hanges. The DSR power is derived from the MAUX auxiliary winding within the main stator, which uses the third harmonic to have high levels of power when starting motors.

MOTOR STARTING

Key to the irrigation application is the ability to acceptlarge impact loads relative to the size of the alternator.
The MAUX system provides over 300% power for 20
seconds which is easily enough for most irrigation motors. The voltage dip will vary according to the level of the impact load but typical TVDs would be 15% with 100% load on, 25% with 200% load on and 35% with 300% load on.

PROTECTION

The ECP28 and ECP32 are IP23 protected, which gives you protection for the following:

IP 2_ Items larger than 12mm diameter

IP _3 Water spray falling at up to 60° from the vertical

Higher protection degrees such as IP45 are available
upon request.

TOTAL+

The optional TOTAL+ level of winding protection is recommended as standard for the irrigation alternators, adding protection against the particles that pass the IP23 protection. It is the ultimate solution to be used when the application or the environment is abusing the insulation of the generator. With this protection level, the grey EG43 varnish on main and exciter stator is replaced by a 0.5 to 2mm thick layer of flexible rubber compound. The black compound acts as a physical barrier to moisture particles and chemical substances. The active rotating parts now have the EG43 added to further enhance protection.