Section 7 Converter equipment

7.1.1 Paragraphs Vol 2, Pt 9, Ch 3, 7.1 Transformers 7.1.2 apply to transformers rated for 5 kVA upwards.

7.1.2 Transformers are to comply with the requirements of the following standards as appropriate:

1. IEC 60076 (all parts): Power transformers

2. IEC 60092-503: Electrical installations in ships – Part 503: Special features – AC supply systems with voltages in the range of above 1 kV up to and including 36 kV; or

3. an acceptable and relevant National Standard amended where necessary for ambient temperature, see Table 3.4.1 Ambient operating conditions,Pt 1, Ch 3,4.5.

7.1.3 Transformers may be of the dry type, encapsulated or liquid filled type.

7.1.4 The temperature rise of the winding of transformers above the ambient temperatures given in Table 3.4.1 Ambient operating conditions, Pt 1, Ch 3, 4.5, when measured by resistance during continuous operation at the maximum rating, is not to exceed:

1. For dry type transformers, air cooled:

   insulation of Class A – 50ºC

   insulation of Class E – 60ºC

   insulation of Class B – 70ºC

   insulation of Class F – 90ºC

   insulation of Class H – 110ºC

2. For liquid filled transformers:

   50ºC – where air provides cooling of the fluid

   65ºC – where water provides cooling of the fluid.

7.1.5 When a transformer is connected to a supply system with harmonic distortion, the rating of the transformer is to allow for the increased heating effect of the harmonic loading. Special attention is to be given to transformers connected for the purpose of reducing harmonic distortion.

7.1.6 The inherent regulation of transformers at their rated output is to be such that the total percentage voltage drop to any point in the installation does not exceed that allowed by Vol 2, Pt 9, Ch 1, 2.1 Quality of power supplies (QPS) 2.1.2.

7.1.7 Transformers, except those for motor starting, are to be double wound.

7.1.8 Liquid fillings for transformers are to be non-toxic and of a type which does not readily support combustion. Liquid filled transformers are to have a pressure relief-device with an alarm and there is to be a suitable means provided to contain any liquid which may escape from the transformer due to the operation of the relief device or damage to the tank.

7.1.9 All transformers are to be capable of withstanding for two seconds, without damage, the thermal and mechanical effects of a short-circuit at the terminals of any winding.

7.1.10 When forced cooling is used, whether air or liquid, there is to be monitoring of the cooling medium and transformer winding temperatures with an alarm should these exceed preset limits. There are to be arrangements so that the load may be reduced to a level commensurate with the cooling available.

7.1.11 When oil-immersed transformers are used, there is to be monitoring for low oil level with an alarm when pre-set limits are crossed. There are to be arrangements so that the load may be reduced to a level commensurate with the cooling available.

7.1.12 Transformers for propulsion power are to be provided with arrangements such that, in the event of excessive winding temperature, an alarm is initiated and:

• the load is reduced to a level commensurate with the cooling arrangements; or
• automatic shutdown of the transformer occurs.

7.1.13 Where liquid-cooled heat exchangers are used in transformer cooling circuits, there is to be provision to detect leakage of the liquid, and the system is to be arranged so as to prevent the entry of liquid into the transformer.

7.1.14 The following tests are to be carried out on all transformers at the manufacturer’s works, and a certificate of tests is to be issued by the manufacturer, see also Vol 2, Pt 9, Ch 1, 1.6 Surveys 1.6.2 and Vol 2, Pt 9, Ch 1, 1.6 Surveys 1.6.3:

1. measurement of winding resistances, voltage ratio, impedance voltage, short-circuit impedance, insulation resistance, load loss, no load loss and current;

2. dielectric tests;

3. temperature rise test on one transformer of each size and type; and

4. where evidence of compliance with Vol 2, Pt 9, Ch 3, 7.1 Transformers 7.1.9 is not submitted for consideration, short-circuit withstand on one transformer of each size and type.

7.2.1 The requirements of Vol 2, Pt 9, Ch 3, 7.2 Semiconductor converters 7.2.2 apply to semiconductor converters rated for 5 kW upwards.

7.2.2 Semiconductor converters are to comply with the requirements of IEC 60146: Semiconductor converters (all parts), or an acceptable and relevant National Standard amended where necessary for ambient temperature, see Table 3.4.1 Ambient operating conditions.

7.2.3 Semiconductor static power converter are to be rated for the required duty having regard to peak loads, system transients and overvoltage.

7.2.4 Converter equipment may be air or liquid cooled and is to be so arranged that it cannot remain loaded unless effective cooling is maintained. Alternatively, the load may be automatically reduced to a level commensurate with the cooling available.

7.2.6 Where forced cooling is used there is to be temperature monitoring of the heated cooling medium with an alarm and shutdown when the temperature exceeds a preset value.

7.2.7 Cooling fluids are to be non-toxic and of low flammability.

7.2.8 Converter equipment is to be so arranged that the semiconductor devices, fuses, control and firing circuit boards may be readily removed from the equipment for repair or replacement.

7.2.9 Test and monitoring facilities are to be provided to permit identification of control circuit faults and faulty components.

7.2.10 Protection devices fitted for converter equipment protection are to ensure that, under fault conditions, the protective action of circuit breakers, fuses or control systems is such that there is no further damage to the converter or the installation.

7.2.11 Converter equipment, including any associated transformers, reactors, capacitors and filters, if provided, is to be so arranged that the harmonic distortion, and voltage spikes, introduced into the ships electrical system are within the limits of Vol 2, Pt 9, Ch 1, 2.1 Quality of power supplies (QPS) 2.1.3 or restricted to a lower level necessary to ensure that it causes no malfunction of equipment connected to the electrical installation. Converter equipment cables may carry high frequency currents that can cause interference. These cables are to be kept as short as possible and installed as far away as possible from sensitive signal cables.

7.2.12 Overvoltage spikes or oscillations caused by commutation or other phenomena, are not to result in the supply voltage waveform deviating from a superimposed equivalent sine wave by more than 10 per cent of the maximum value of the equivalent sine wave.

7.2.13 When converter equipment is operated in parallel, load sharing is to be such that under normal operating conditions overloading of any unit does not occur and the combination of paralleled equipment is stable throughout the operating range.

7.2.14 When converter equipment has parallel circuits there is to be provision to ensure that the load is distributed uniformly between the parallel paths.

7.2.15 Transformers, reactors, capacitors and other circuit devices associated with converter equipment, or associated filters, are to be suitable for the distorted voltage and current waveforms to which they may be subjected and filter circuits are to be provided with facilities to ensure that their capacitors are discharged before the circuits are energised.

7.2.16 Any regenerated power developed during the operation of converter equipment is not to result in disturbances to the supply system voltage and frequency which exceeds the limits of Vol 2, Pt 9, Ch 1, 2.1 Quality of power supplies (QPS).

7.2.17 Where control systems form an integral part of semiconductor equipment, they are to be designed and manufactured with regard to the environmental conditions to which they will be exposed in service and their performance is to be demonstrated during the test and trials programme.

7.2.18 Tests at the manufacturer’s works of converter equipment and any associated reactors or filters are to include the high voltage test of Vol 2, Pt 9, Ch 12, 1.1 Testing, a temperature rise test on one of each size and type of converter equipment, and such other tests as may be necessary to demonstrate the suitability of the equipment for its intended duty. Details of tests are to be submitted for consideration when required, see also Vol 2, Pt 9, Ch 1, 1.6 Surveys 1.6.2.

7.3.1 The requirements of this sub-Section apply to all uninterruptible power systems (UPS) intended to maintain Mobility or Ship Type systems, or provide emergency services. This sub-Section is in addition to the requirements of Vol 2, Pt 9, Ch 3, 7.1 Transformers to Vol 2, Pt 9, Ch 3, 7.2 Semiconductor converters and Vol 2, Pt 9, Ch 2, 7 Batteries, as applicable.

7.3.2 UPS units are to be constructed in accordance with IEC 62040: Uninterruptible power systems (UPS)(all parts), or an acceptable and relevant National or International Standard.

7.3.3 The operation of a UPS is not to depend upon external services.

7.3.4 The type of UPS unit employed, whether off-line, line-interactive or on-line, is to be appropriate to the power supply requirements of the connected load equipment.

7.3.5 An external bypass, that is hardwired and manually operated, is to be provided for UPS to allow isolation of UPS for safety during maintenance and maintain continuity of load power.

7.3.6 UPS units are to be monitored and an audible and visual alarm is to be initiated in the navigating bridge or the engine control room, or an equivalent attended location for:

• power supply failure (voltage and frequency) to the connected load;
• earth fault;
• operation of battery protective device;
• battery discharge; and
• bypass in operation for on-line UPS units.

7.3.7 UPS units required to provide emergency services are to be suitably located for use in an emergency.

7.3.8 UPS units utilising valve-regulated sealed batteries may be located in compartments with standard marine or industrial electrical equipment provided that the arrangements comply with Vol 2, Pt 9, Ch 2, 7.3 Location 7.3.5. Ventilation arrangements in accordance with IEC 62040-1: Uninterruptible power systems (UPS) – Part 1: General and safety requirements for UPS, or an acceptable and relevant National or International Standard, may be considered to satisfy the requirements off Vol 2, Pt 9, Ch 2, 7.5 Thermal management and ventilation 7.5.10.

7.3.9 Output power is to be maintained for the duration required for the connected equipment.

7.3.10 The UPS battery capacity is, at all times, to be capable of supplying the designated loads for the time specified. Where it is proposed that additional circuits are connected to the UPS unit, details verifying that the UPS unit has adequate capacity are to be submitted for consideration, see Vol 2, Pt 9, Ch 1, 1.7 Alterations and additions.

7.3.11 On restoration of the input power, the rating of the charge unit is to be sufficient to recharge the batteries in a reasonable time while maintaining the output supply to the load equipment.

7.3.12 Tests at the manufacturer’s works or after installation on board are to include such tests necessary to demonstrate to the Surveyor’s satisfaction the suitability of the UPS unit for its intended duty and location. As a minimum, the following tests are required:

• a temperature rise test
• battery capacity test;
• a ventilation rate test of both the equipment housing and the space into which it is to be located, see also Vol 2, Pt 9, Ch 2, 7.5 Thermal management and ventilation; and
• functional testing, including operation of alarms.

Details of tests are to be submitted for consideration when required, see also Vol 2, Pt 9, Ch 1, 1.6 Surveys 1.6.2.

7.3.13 Where the supply is to be maintained without a break following a power input failure, this is to be verified after installation by practical testing.

7.3.14 UPS units utilising lithium battery systems as energy storage devices are to be in accordance with the following sub-Sections of these Rules as applicable and to the recommendations of the battery manufacturer:

• Vol 2, Pt 9, Ch 1, 1.4 Documentation required for design review;
• Vol 2, Pt 9, Ch 2, 7.1 General requirements;
• Vol 2, Pt 9, Ch 2, 7.2 Design and construction;
• Vol 2, Pt 9, Ch 2, 7.3 Location;
• Vol 2, Pt 9, Ch 2, 7.4 Installation;
• Vol 2, Pt 9, Ch 2, 7.5 Thermal management and ventilation; and
• Vol 2, Pt 9, Ch 12, 1.1 Testing.