Transport Publication TP 127 E
14.1 Transformers, except those used for motor starting shall be double-wound (two separate windings); auto-transformers shall be used only for reduced voltage motor starting or other special applications.
14.2 Transformers shall be installed in well-ventilated compartments, accessible only to authorized personnel except that air-cooled transformers provided with means of protection against accidental contact with live parts need not be installed in special compartments.
14.3 Liquid-cooled transformers shall be housed in a metallic compartment having adequate means for drainage of liquid leakage; the cooling liquid shall be non-flammable and non-toxic.
14.4 Suitable arrangements shall be provided for cooling and containing all the liquid which might escape from a damaged tank.
14.5 Transformers and their connections shall be protected against mechanical damage, condensation and corrosion.
14.6 Suitable terminals, clearly marked, shall be provided in an accessible position, convenient for external connections; the terminals shall be effectively secured and shall be so spaced or shielded that they cannot be accidentally grounded, short-circuited or touched.
14.7 Liquid-cooled transformers shall be of the conservator type and shall be so designed that, under all conditions with the ship inclined 22 ½° from the normal or when the trim is 10°, they operate without risk of spilling liquid; if provision is made for breathing, a suitable dehydrator shall be provided.
14.8 Where transformers constitute an essential part of the electrical supply system necessary for maintaining the auxiliary services indispensable for the propulsion and safety of the ship, they shall be of sufficient rating and number and so arranged as to ensure that transformer failure will not prevent the supply of power to the indispensable auxiliary services.
14.9 Where transformers are arranged to operate in parallel, their coupling groups shall be compatible and their no-load voltage ratios equal; the rated output of the smallest transformer in the group shall be not less than half the rated output of the largest transformer in the group.
14.10 All transformers shall be capable of withstanding without damage, the effects of a short circuit at the terminals of any winding for two seconds duration.
14.11 The temperature rise of dry type transformers, measured during continuous operation at the maximum rating, shall not exceed the limits given in Table 14-1.
Table 14-1: Dry Type Transformers
Limits of Temperature Rise for Continuous
Duty – Degrees Celsius Based on 40°
C
. Ambient
|
Copper temperature rise by resistance |
Hottest spot
temperature rise |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Insulation Class | Insulation Class | |||||||||
| Part | A
(105sys) |
E | B
(150sys) |
F
(185sys) |
H
(220sys) |
A | E | B | F | H |
| Insulated winding | 55 | 70 | 80 | 115 | 150 | 65 | 85 | 110 | 145 | 180 |
NOTE: Metallic parts in contact with or adjacent to insulation shall not attain a temperature in excess of that indicated for the hottest spot copper temperature in the above table adjacent to that insulation.
14.12 Transformers which are equipped, and which are designed for forced air cooling, shall be fitted with an alarm at the main control station, which will indicate either of the following conditions:
- loss of ventilation; or
- high temperature.
15. Static Power Supply Units
15.1 These units employ semi-conductor components to effect power conversion as follows:
- AC - DC : Rectifiers including Battery Charging Rectifiers and DC Power Supplies
- DC - AC : Inverters
- AC - AC : Frequency Converters (Changers)
- DC - DC : Voltage Converters
- UPS Systems: Uninterruptible Power Supply Systems
15.2 The units shall be provided in adequately designed steel cabinets or enclosures, either floor or wall mounted as required.
15.3 Convection cooling without forced ventilation is to be preferred.
15.4 Where openings are required in the top of the cabinet to facilitate or enhance natural convection cooling, such openings shall be protected by a suitable drip cover.
15.5 Where forced ventilation must be employed, the circuit shall be designed upon loss of cooling air, to:
- trip the power supply to the unit; or
- activate and alarm at the main control station.
15.6 The units shall be installed in such a manner that the circulation of cooling air shall not be impeded or restricted, and so that the ambient temperature of the inlet air to the enclosure does not exceed that specified for the unit operating environment.
15.7 The units shall not be mounted near heat sources.
15.8 Circuit breakers or fuses shall be provided to protect the input and output of the units.
15.9 Mercury-type fungus protection, even in minute quantities, will damage selenium-type rectifier cells and shall not be used in their vicinity.
15.10 For units designed to operate in parallel with other equipment, precautions shall be taken to ensure that, within the specified loading conditions, load sharing is such that overloading of any unit does not occur and that the combination of the parallel equipment is stable.
15.11 Inverters:
15.11.1 The safety of the vessel shall not be compromised by the installation of Inverters over 1 kW used for non-essential services.
15.11.2 Inverters shall be bonded to the vessels ground conductor in accordance with Section 4.
15.11.3 Receptacles fed from an inverter shall be grounded to the vessel ground in accordance with Section 4.
15.11.4 Distribution systems fed from an inverter shall be fitted with a suitable means of indicating ground faults.
15.11.5 Inverters shall be fitted with a Voltmeter to indicate the output voltage.