Ship Electrical Standards (2002) | TP 127

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Transport Canada > Marine Safety Home Page > Transport Publications | Marine Safety > Ships Electrical Standards (2002) | TP 127 | Marine Safety

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16. Generating Plant and Motors

16.1 When the number and ratings of the required ship's service generating sets is determined, consideration shall be given to the normal and maximum demand loads as well as the safe and efficient operation of the ship when at sea and in port; the number and rating of generating sets shall be sufficient to ensure the operation of the auxiliary services indispensable for the propulsion and safety of the ship, even when one generator or its prime mover is out of service.

16.2 In addition, for ac ship's service generators consideration shall be given to the starting kVA and power factor of squirrel cage motors particularly in regard to the effect of the magnitude and duration of resulting transient voltage changes.

16.3 When ac generating sets operate in parallel and are carrying initially the minimum load necessary for the operation of the ship, they shall have sufficient reserve capacity to permit the starting of the largest idle motor on the system without causing any operating motor to stall or any adverse effect on other equipment due to the transient voltage variation.

16.4 Prime movers for driving electrical generators intended for supplying ship's service systems shall be continuously rated; generating plant for ship's service shall be suitable for continuous duty at the full and rated load; they shall have an overload capability comparable with the overload capability of the driven generators; each prime mover shall, in addition, be under the control of an efficient operating governor capable of limiting the speed, when full load is suddenly removed, to at least 5 per cent less than that of the overspeed trip setting; the overspeed trip shall also be equipped with a means for manual tripping.

16.5 Where a turbine-driven dc generator is arranged to run in parallel with other generators, a switch with normally closed contacts shall be fitted on each turbine emergency governor to open the generator circuit breaker when the emergency trip functions.

16.6 The automatic governing characteristics of the prime movers for ac generating sets operating in parallel shall be such that, for loads within the limits of 20% and 100% of the total connected generating capacity, the load of any generating set does not normally differ from its proportionate share of the total load by more than 25% of its full rating, or 15% of the rated full-load output of the largest machine, whichever is the less.

16.7 Each generator shall be provided with suitable terminals or leads clearly marked, in an accessible position, convenient for external connections and effectively secured, spaced and shielded so that they cannot accidentally be grounded, short-circuited or touched; the generator terminals shall be enclosed in a terminal box so constructed that the incoming cables can be led into it in a manner which will not impair the original integrity of the box.

16.8 The temperature rise of each of the various parts of ac and dc motors and generators when tested in accordance with their rating, shall not exceed the values set forth in Tables G, H and I, based on an ambient temperature as stated in section 16 of these Standards.

16.9 Classes of insulation A, B, F and H shall be in accordance with the most recent edition of Publication No. 85 issued by the International Electrotechnical Commission.

16.10 Means shall be provided to enable the voltage of each generator to be adjusted.

16.11 Each ac service generator, unless of the self-regulated type, shall be provided with a separate automatic voltage regulator capable of withstanding shipboard vibrations.

16.12 Emergency generators shall be capable of establishing voltage without auxiliary means under all conditions of operation.

16.13 The equipment provided for adjusting the voltage of d.c. generators shall be capable of varying the voltage at any load between no load and full load to within:

0.5% of rated voltage for generators of rating exceeding l00 kW ; or
1.0% of rated voltage for generators of ratings not exceeding l00 kW.

16.14 The inherent voltage regulation of ship's service dc generators designed in relation to the speed regulation and governing of the prime movers shall be as follows:

Shunt or stabilized shunt-wound generators rated at 25 kW and above, shall comply with the following requirements:

when the voltage has been set at full load to its rated value, the removal of the load shall not cause a permanent increase of the voltage greater than 15% of the rated voltage; and
when the voltage has been set either at full load or at no load, the voltage obtained at any value of the load shall not exceed the no-load voltage;

compound-wound generators rated at 25 kW and above shall be so designed in relation to the governing characteristics of the prime mover that, with the generator at full-load operating temperature and starting at 20% load with voltage within 1% of rated voltage, it shall give at full load a voltage within 1.5% of rated voltage; the average of ascending and descending voltage regulation curves between 20% load and full load shall not vary more than 3% from rated voltage; and
ship's service generators which are of the shunt type shall be provided with an automatic voltage regulator; an automatic voltage regulator shall also be provided for all ship's service generators driven by variable speed engines used also for propulsion purposes whether these generators are of the shunt, stabilized shunt or compound-wound type.

16.15 The excitation system of ac generators rated 25 kW and above shall comply with the following requirements:

each ac generator for ship's service driven by its prime mover having governor characteristics complying with subsection 16.6 shall be provided with an excitation system capable of maintaining voltage under steady conditions within plus or minus 2.5% of rated voltage for all loads between zero and rated load at rated power factor; these limits may be increased to plus or minus 3.5% for emergency sets;
when the generator is driven at rated speed, giving its rated voltage and it is subjected to a sudden change of symmetrical load within the limits of specified current and power factor, the voltage shall not fall below 85% nor exceed 120% of the rated voltage; the voltage of the generator shall then be restored to within plus or minus 3% of the rated voltage for the main generator sets in not more than 1.5 seconds; for emergency sets these values may be increased to plus or minus 4% and not more than 5 seconds respectively; in the absence of precise information concerning the maximum values of the sudden loads, the following conditions shall be assumed: 60% of the rated current with a power factor of between 0.4 lagging and zero to be thrown on with the generator running at no load, and then withdrawn after steady state conditions have been reached; and
under short-circuit conditions, the generator with its excitation system shall be capable of maintaining a current of at least three times its rated value for a duration of up to 2 seconds, unless protection selectivity requirements exist which allow a shorter duration and provided that, in any case, the safety of the installation is assured.

16.16 When ac generators are operated in parallel, the reactive loads of the individual generating sets shall not differ from their proportionate share of the total reactive load by more than 10% of the rated reactive output of the largest machine or 25% of the smallest machine where this value is less than the former.

16.17 The design of dc generators and their connections shall be such that when they operate in parallel, the individual load on each machine does not normally differ from its pro-portionate share of the load by an amount greater than 12% of the rated full load of the largest machine or 25% of the rating of the individual machine in question; this requirement applies when the combined load on the sets is varied between 20% and 100% of the combined ratings; such load sharing shall not result in over-loading the smaller set; for each generator of a group required to run in parallel, the voltage drop across the series field and its connection to the switchboard shall be approximately equal.

16.18 DC generators which are required to run in parallel shall be stable in operation at all loads from no load to full load.

16.19 The series windings of 2-wire dc generators shall be connected to the negative terminal of the machine.

16.20 Every equalizer connection shall have a cross-sectional area not less than half that of the negative connection from the generator to the switchboard.

16.21 The components of the excitation system for ac generators, including automatic voltage regulation, if used, shall be of a type suitable for shipboard conditions and be capable of operating under all specified conditions of steady and transient load, including short-circuit.

16.22 Where water cooling is used, the cooler shall be so arranged as to avoid entry of water into the machine whether by leakage or condensation in the heat exchanger.

16.23 Means shall be provided to prevent accumulation of moisture and condensation within the machines, especially when they are idle for appreciable periods.

16.24 Machines shall be so constructed that when running at any and every working speed, all revolving parts are well balanced.

16.25 Measures shall be, if necessary, taken to prevent the circulation of current between the shaft and the bearings.

16.26 Generators and motors shall have efficient and continuous lubrication at all probable inclinations, running speeds and all normal working bearing temperatures.

16.27 Means shall be provided to prevent the lubricant from creeping along the shaft or otherwise gaining access to the insulation of the machine or any live part thereof.

16.28 Every oil-lubricated bearing shall be provided with a suitable overflow which, while permitting efficient lubrication when the machine is running, prevents the bearings from containing excess of oil.

16.29 Where ring lubrication is employed, the rings shall be so constrained that they cannot leave the shaft.

16.30 Every machine of rating 100 kW or greater having self-lubricated sleeve bearings shall be fitted with a bearing inspection lid and means for visual indication of bearing oil level.

16.31 Shafting materials for motors and generators above 375 kW which are essential to the safety of the ship shall be constructed, installed and inspected in accordance with Schedule VI of the Marine Machinery Regulations.

16.32 Space heaters are to be supplied integral with all generators; these heaters shall be energized at any time that the temperature of the windings or metal parts of the generator are lower than the ambient temperature; the heaters shall be placed in such a location that warm air will pass over the windings and commutator; this movement of air may be accomplished by convection or forced air circulation; the following table shows recommended size of heater in terms of weight, excluding shaft.

WEIGHT 0F GENERATOR in Kilograms	WATTS OF SPACE HEATER
0 - 454	100
454 - 1361	250 - 500
1361 - 2722	500 - 1000
2722 - 4636	1000 - 1250
above 4636	200 watts / 1000 kg

16.33 Electronic governors controlling the speed of the prime-mover for ship's service ac generators and ship's service dc generators shall have two power supplies, one of which shall be a battery; in the event of a "normal" supply failure the governor shall be automatically transferred to the "alternative" battery power supply; an audible and/or visual alarm shall be provided in the main machinery control area to indicate that the governor has transferred to the battery supply; the prime-mover shall be equipped with a separate overspeed device to prevent runaway if a failure should render the governor inoperative; the alternative battery supply shall be arranged for trickle charge to ensure the battery is always in a fully charged state; each governor shall be protected separately so that a failure in one governor will not cause failure of other governors; a mechanical back-up governor may be provided in lieu of the alternative battery supply; the mechanical governor shall be of a suitable type and shall automatically assume control of the engine in the event of electronic governor failure.

16.34 Ship's service alternating-current generators of 500 kW and above, shall be provided with means for obtaining the temperatures of the stationary windings; a minimum of one embedded temperature detector per phase is to be provided for this purpose on the hot end of the machine; the temperatures are to be indicated at a convenient location, preferably the generator control panel.

TABLE 16-1
LIMITS OF OBSERVABLE TEMPERATURE RISE FOR DC MOTORS
AND GENERATORS BASED ON 50°C AMBIENT TEMPERATURE

Item	Machine Part	Type of Enclosure	Method of Temperature Determination	Class of Insulation
Item	Machine Part	Type of Enclosure	Method of Temperature Determination	A	B	F	H
1	Armature Windings	Driproof & open Totally Enclosed	Thermometer Resistance Thermometer Resistance	40 60 45 60	60 90 65 90	80 120 85 120	100 145 105 145
2	Multi-layer Field Windings	Driproof & open Totally Enclosed	Thermometer Resistance Thermometer Resistance	40 60 45 60	60 90 65 90	80 120 85 120	100 145 105 145
3	Single-layer field windings with exposed un-insulated surfaces and bare copper windings	Driproof & open Totally Enclosed	Thermometer Resistance Thermometer Resistance	50 60 55 60	70 90 75 90	95 120 100 120	120 145 125 145
4	Cores and mechanical parts in contact with or adjacent to the insulation	Driproof & open Totally Enclosed	Thermometer Thermometer	40 45	60 65	80 85	100 105
5	Commutators and collector rings	All	Thermometer	55	75	95	115

TABLE 16-2
LIMITS OF OBSERVABLE TEMPERATURE RISE FOR AC GENERATORS
BASED ON 50° C AMBIENT TEMPERATURE

Machine	Method of Temperature Determination	Class of Insulation
Machine	Method of Temperature Determination	A	B	F	H
Armature Windings
(a) All ratings	Resistance	50	70	95	115
(b) 1563 kW and less	Embedded Detector	60	80	105	130
(c) Over 1563 kW	Embedded Detector	55	75	100	125
Field Windings
(a) Salient Pole	Resistance	50	70	95	115
(b) Cylindrical Rotor	Resistance	-	75	95	115

TABLE 16-3
LIMITS OF OBSERVABLE TEMPERATURE RISE FOR AC MOTORS

Machine	Method of Temperature Determination	Ambient 50m C Class of Insulation
Machine	Method of Temperature Determination	A	B	F	H
Windings
(a) All but (b) and (c)	Resistance	50	70	95	115
(b) Totally enclosed non-ventilated enclosures only	Resistance	55	75	100	125
(c) Encapsulated only	Embedded Detector	55	75	100	-
(d) 1100 kW and less	Embedded Detector	60	80	105	130
(e) over 1100 kW	Embedded Detector	55	75	100	125
Field Windings of Synchronous Motors
(a) Salient Pole	Resistance	50	70	95	115
(b) Cylindrical Rotor	Resistance	-	75	95	115