8Physical and mechanical requirements#
8.1Engine#
The generator engine shall be an internal combustion type, complying with the requirements of AS 4594. The engine shall meet all the performance requirements of the generator set under the specified operating conditions and shall be suitable to operate with fuels listed in Fuel Quality Standard Act 2000. The Time Between Overhauls (TBO) should be more than 4000 hours for prime rated applications.
The prime mover and generator should be direct coupled, and both shall be mounted on a common base plate. Anti-vibration mounting shall be provided between generator set and base plate.
8.1.1Cooling#
A forced air or closed loop water cooling system shall be provided that ensure continuous operation of the generator in a range of ambient temperature and humidity prescribed in Figure 1.1 of AS 2578-Part 1.
For closed loop water cooling systems, an engine driven pump and fan are preferable.
8.1.2Air intake#
The engine air intake system shall include dry type air filters.
8.1.3Exhaust#
Exhaust gas system shall be of mild steel and all connections shall be flanged using heat resistant gaskets containing no asbestos and with outlet preventing ingress of dust or storm water into the cooling system.
A silencer shall be provided to reduce noise to the specified levels.
All exhaust pipe surfaces shall be insulated. Insulation shall be suitably rated mineral wood or fibreglass and shall be fixed with corrosion resistant self-tapping screws.
8.1.4Lubrication#
The lubricating oil system shall be self-priming and splash type by means of an engine driven integral pump. The pump shall have on the suction side a coarse strainer and on the delivery side a duplex ‘full flow’ fine filter complete with changeover cock incorporating pressure by-passes to facilitate oil flow to the engine should the filter become blocked. The lubrication system capacity shall be sufficient to enable to run continuously for 12 hours at any load without replenishment.
A manual oil level indicator shall be provided.
8.1.5Starting#
The generator shall be started either electrically via an “ON” switch, or via a recoil starter (pull start).
For electrically started generators a 12 V starter motor shall be used. The equipment shall include an adequately rated lead/acid battery together with an automatic mains energised battery charger. The charger shall have a continuous output rating sufficient to recharge the battery from 1.8 V/cell to a fully charged condition in a period of eight hours. A charging indicator or charging parameter indication should be provided in the control panel.
The battery shall be capable of providing at least six starting cycles within a period of five minutes and shall not affect the correct operation of the control system during the start of the engine.
Where a recoil starter is used, it shall be equipped with a compression release mechanism.
8.1.6Governor#
The governor of the engine shall be mechanical/electronic type and be capable of fine governing of speed to Class A1 of AS 4594.
8.1.7Fuel system and storage#
The fuel tank shall be integral within the generator unit and without refuelling shall provide for at least four hours continuous running at full load capacity. The fuel tank shall be complete with fill, vent, drain, overflow line, and level indication. A low level switch shall be provided for indication at control panel. A fuel water separator shall be provided in case the fuel is diesel.
To allow for additional fuel capacity, it is desirable that the generator has provision for auxiliary plug-in fuel tanks.
A manual shut-off valve and filter shall be provided in the supply line to the engine. The fuel system shall incorporate facilities to overcome fuel starvation due to high ambient temperatures.
8.2Generator#
8.2.1General#
The generator shall be single phase, two wire, brushless, self-exciting and self-regulating type. The degree of protection for the generator and exciter shall be not less than IP 23 in accordance with AS 60529. Cooling of the generator shall be by a radial-flow fan. Generator bearings shall be of the ball or roller type, and prepacked with sufficient grease for operating over long periods without replenishment.
The generator windings shall be air cooled, with Class F insulation (NEMA classification) and shall be varnish impregnated to suit the specified environment conditions and heated to compensate for condensation propensity.
Generators shall be equipped with a protection system to protect a motor from winding failure and prevent starting of the generator in the event of high winding temperature. The protection system may include current sensitive devices or temperature sensitive devices.
8.2.2Excitation#
The exciter shall be brushless and self-excited type with rotating silicon rectifiers, static voltage regulator and compounding equipment. The voltage regulator shall maintain its setting for long periods without adjustment.
The excitation system shall generate a sufficient current to automatically disconnect a protective device within 0.4 seconds in the event of a short circuit, when the Fault Loop Impedance of the installation is in accordance with the principles of Table 8.1 of AS 3000.
The exciter shall have Class F insulation with Class B temperature rise and be of the enclosed ventilated type having the same degree of protection as the generator enclosure.
A solid state type automatic voltage regulator (AVR) shall be provided with following minimum facilities:
- under frequency roll off
- over frequency roll off
- excitation over current protection.
8.3Enclosure#
The relevant clauses of enclosures as defined in MRTS201 is applicable to this Technical Specification as specified by the Principal's representative. Additional requirements are listed below.
All moving parts that may cause injury to persons shall be protected by barriers to prevent unintentional personal contact with such parts. The protection shall be provided by guards, enclosures, railings or fences.
The combined generator and engine unit shall be integrally coupled and enclosed in a mobile acoustic and fireproof casing suitable for outdoor operation. Protection rating of the generator integral with enclosure shall be at least IP44 in accordance with AS 60529.
The enclosure shall be provided with the following facilities:
- lifting points/pad mounting
- lockable covers with safety guards allowing adequate access for inspection and maintenance, and screening to prevent entry of vermin
- secure cable access into the enclosure
- sufficient ventilation to prevent accumulation of dangerous gases and creation of hot spots.