BS 5000-25:1981 download.Specification for Rotating electrical machines of particular types or for particular applications.
1 Scope and object
BS 5000-25 applies to mill auxiliary motors. It specifies mechanical and electrical requirements and dimensions for foot-mounted d.c. mill auxiliary motors for heavy duty steel mill service. It covers series, compound, shunt, compositely and separately excited motors and motors with compensating winding, with rated voltages of 230 V. 460 V and 550 V, with rated outputs 3.75 kW to 243 kW, and rated speeds 360 rev/mm to 1 130 rev/mm.
2 Mounting
The type of construction and mounting shall be IM 1004 as defined in IEC Publication 34-7, i.e. the shaft, having two conical extensions, is horizontal and the motor has its feet down.
3 Dimensions and tolerances
The mounting dimensions and tolerances associated with a particular frame size shall be generally in accordance with Table I and Figure 1, page 7.
4 Enclosure and cooling
Motors shall have a degree of protection not less than IP 44 as defined in IEC Publication 34-5 and shall have one of the following enclosures and methods of cooling as defined in IEC Publication 34-6:
a) totally-enclosed (frame surface cooled with free convection, IC 40);
b) duct ventilated (inlet duct circulated by independent coolant system, JC 17).
5 Convertibility
Totally-enclosed and ventilated motors shall be mutually convertible by the addition or removal of suitable covers. When converting a totally-enclosed motor to ventilated, or vice versa, it is permissible to remove or add an internal fan.
6 Air flow
Ventilated motors shall meet the specified rated outputs when supplied with the air quantities given in Table III at the relevant pressures.
The direction of air flow can be in either direction through the motor.
7 Connection leads
The standard position of the connecting leads shall be on the right side of the motor when facing the drive end (i.e. the end opposite the commutator). Alternatively, conduit or terminal boxes may be provided when specified by the purchaser.
8 Shaft extensions
The shaft tapers shall be either 1: 9.6 or 1: 10. A shaft extension key, a locking device and a nut shall be provided on the drive end only. A shaft guard (thimble) shall be provided on the non-drive end.
The dimensions for the shaft extensions and key shall be in accordance with Table II.
NOTE It is recommended that the armature construction shall enable the motor shaft to be replaceable.
9 Armature end play
The axial end play of the armature shall not exceed 5 mm.
10 Rated values
Motors shall be rated in accordance with the information listed in Table 111. They shall comply with the temperature-rise requirements specified in Clause 13 when tested on a direct current supply having no appreciable ripple (e.g. that obtained from a rotating generator source).
Standard rated voltages for individual motors shall he 230 V, 460 V and 550 V. Other voltages may be agreed between the manufacturer and the purchaser.
Motors rated for 230 V shall be capable of operating up to 500 V. Maximum operating voltage levels of motors rated for 460 V and 550 V shall be agreed between the manufacturer and the purchaser.
For motors operating at voltage levels above the standard rated value, the maximum load torques specified in Table 111 may be reduced.
11 Motors supplied from rectified power supplies
Motors shall be suitable for satisfactory operation at the rated outputs listed in Table III when supplied from a variable voltage rectified power source (i.e. thyristor converter). The ripple content of this power source should not exceed that derived under similar circumstances from threephase 50 Hz or 60 Hz, six controlled pulses ( 300 Hz or 360 Hz predominant ripple frequency respectively) and with the phase control of the rectifier not exceeding 20 % of the free-firing condition (i.e. 460 V mean d.c. level from 415 V a.c. r.m.s. line-to-line voltage).
NOTE When motors are operated from a rectified a.c. supply other than described above, the performance may differ materially from that of similar motors when operated from a d.c. source having the same effective value of voltage. At the same rated loads, the temperature rise, speed regulation, and noise level may be increased and commutation could be adversely affected. The degree of difference will depend upon the level of ripple currents circulated in the motor circuit and is more significant when the rectifier pulse number is low (<6) and the amount of phase control is high (>20 %).
When motors are operated from rectified power supplies, as indicated above, bearing currents may become evident due to high-frequency ripple currents being transmitted through the capacitive coupling between the armature winding and core and returned through the eart.h path to the transformer secondary. While these ripple-current levels are normally small in magnitude, they may result in long-term damage to the bearing surfaces under certain conditions.
12 Field voltage
The standard rated voltage for the field windings of separately excited motors shall be 230 V. Other voltages may be agreed between the manufacturer and the purchaser.
13 Temperature rise
The temperature rise of any winding at rated output and duty, at an ambient temperature not exceeding 40 °C, shall be not greater than 75 K when measured by thermometer or 110 K when measured by resistance. The temperature rise of other parts, such as armature iron, commutator, brush-holders, brushes, pole tips, etc., shall not be such that it will cause the part to detract from the operational performance or the life expectancy in any respect.
The temperature rise may be measured either by resistance or by thermometer method to demonstrate conformity with this standard. A load test to confirm the short-time duty type (S2) and intermittent periodic duty type (S3) ratings shall commence only when the windings and other parts of the machine do not deviate by more than ± 5 °C from the ambient temperature.
14 Ambient temperature and altitude
Motors shall he suitable for operation at any temperature between — 30 °C and + 40 °C and at an altitude not exceeding 1 000 m.
15 Field standstill heating
When supplied at the rated voltage, the separately-excited field windings of shunt and compound motors shall be capable of full continuous excitation at standstill without exceeding the temperature rise specified in Clause 13.
21 Maximum speed
The motor shall be capable of running without damage at the appropriate maximum safe operating speed given in Table III.
22 Rating plate marking
The following minimum information shall be given on all rating plates:
1) The manufacturer’s name.
2) The year of manufacture or a code for such, which may be included in the serial number.
3) The manufacturer’s serial number.
4) The manufacturer’s type designation.
5) The frame designation and shaft taper.
6) The number and date of the specification
[e.g. IEC 3413(198O)]2).
7) The rated voltage and “d.c.” or “direct current”.
8) The rated output (kW).
9) The time rating at rated output.
10) The current at rated output.
11) The speed at rated output (rev/mm).
12) The maximum safe operating speed (rev/mm).
13) Field winding connections (shunt, compound,
series or separately excited).
14) The excitation voltage.
15) The class of insulation.
16) The mass of the motor (kg).
17) The type of enclosure (as supplied).
18) The airflow (m3/s) and pressure (Pa) for
continuous rating, ventilated.