Section 6 Generators

6.1.1 Generators are to comply with the general requirements as specified within Vol 2, Pt 9, Ch 3, 6.1 General requirements.

6.1.2 The application of shaft material for main engine-driven generators where the shaft is part of the propulsion shafting is to comply with the Rules for Manufacture, Testing and Certification of Materials (hereinafter referred to as the Rules for Materials) and are to be manufactured under LR survey.

6.1.3 Generators that form part of the electrical propulsion systems are to have at least one embedded temperature detector (ETD) in each phase of the machine winding in locations which may be subjected to the highest temperature. Where there are two coil sides per slot the ETDs are to be located between the insulated coil sides in the slot, see Vol 2, Pt 4, Ch 5, 4.1 General 4.1.4.

6.1.4 A high bearing temperature alarm is to be provided where the generators of 100 kW and above are supplied with forced lubrication.

6.1.5 A low lubricating oil pressure alarm is to be provided for generators that are supplied with forced lubrication.

6.2.1 For generator ratings the applicable requirements of Vol 2, Pt 9, Ch 3, 6.2 Ratings are to be complied with.

6.2.2  Generators are to be capable of an overload power of not less than 10 per cent at their rated power factor for a period of 15 minutes without injurious heating.

6.3.1 For generator temperature rise the applicable requirements of Vol 2, Pt 9, Ch 3, 6.3 Temperature rise are to be complied with.

6.4.1 Each alternating current generator, unless of the self-regulating type, is to be provided with automatic means of voltage regulation; voltage build-up is not to require an external source of power. Provision is to be made to safeguard the distribution system should there be a failure of the voltage regulating system resulting in a high voltage.

6.4.2 The voltage regulation of any alternating current generator with its regulating equipment is to be such that at all loads, from zero to full load at rated power factor, the rated voltage is maintained within ±2,5 per cent under steady conditions. There is to be provision at the voltage regulator to adjust the generator no-load voltage.

6.4.3 Generators and their excitation systems, when operating at rated speed and voltage on no-load, are to be capable of absorbing the suddenly switched, balanced, current demand of the largest motor or load at a power factor not greater than 0,4 with a transient voltage dip which does not exceed 15 per cent of rated voltage. The voltage is to recover to rated voltage within a time not exceeding 1,5 seconds. In the absence of precise data, the applied load is to be not less than 50 per cent of rated kVA at a power factor not greater than 0,4.

6.4.4 The transient voltage rise at the terminals of a generator is not to exceed 20 per cent of rated voltage when rated kVA at a power factor not greater than 0,8 is thrown off. When a generator is supplying any load between 25 per cent and 100 per cent of rated load, and a load equal to 25 per cent rated load at a power factor of 0,8 is suddenly removed, the transient voltage rise at the terminals of the generator is not to exceed 7,5 per cent.

6.4.5 Generators and their voltage regulation systems are to be capable of maintaining, without damage, under steady state short circuit conditions a current of at least three times the full load rated current for a duration of at least two seconds or where precise data is available for the duration of any time delay which may be provided by a tripping device for discrimination purposes. The generator terminal voltage is not to exceed 130 per cent of the rated voltage when the short circuit is removed.

6.4.6 Generators required to run in parallel are to be stable from no load (kW) up to the total combined full load (kW) of the group, and load sharing is to be such that the load on any generator does not normally differ from its proportionate share of the total load by more than 15 per cent of the rated output (kW) of the largest machine or 25 per cent of the rated output (kW) of the individual machine, whichever is less.

6.4.7 When generators are operated in parallel, the kVA loads of the individual generating sets are not to differ from the proportionate share of the total kVA load by more than five per cent of the rated kVA output of the largest machines.

6.4.8 For ELS notation, see Vol 2, Pt 9, Ch 1, 3.2 General requirements 3.2.5.

6.5.1 Machines are to withstand on test, without injury, the momentary overload of an excess current of 50 per cent for 30 seconds after attaining the temperature rise corresponding to rated load, the terminal voltage being maintained as near the rated value as possible. The foregoing does not apply to the overload torque capacity of the prime mover.

6.6.1 For generator enclosures the applicable requirements of Vol 2, Pt 9, Ch 3, 6.5 Machine enclosure are to be complied with.

6.7.1 For direct current generators the applicable requirements of Vol 2, Pt 9, Ch 3, 6.6 Direct current machines are to be complied with.

6.8.1 For survey and testing of generators the applicable requirements of Vol 2, Pt 9, Ch 3, 6.7 Survey and testing are to be complied with.