GB/T 14711-2025General requirements for safety of small and medium size rotating electrical machines (English PDF)

Foreword

This document was drafted in accordance with the rules given in GB/T 1.1-2020 “Directives for standardization — Part 1: Rules for the structure and drafting of standardizing documents”.

This document replaces GB/T 14711-2013 “General requirements for safety of small and medium size rotating electrical machines”. Compared with GB/T 14711-2013, apart from structural and editorial changes, the main technical changes are as follows:

a) deleted the provision that small power motors manufactured to GB/T 5171 could also be assessed against GB/T 12350 (see Clause 1 of the 2013 edition);

b) added marking and instruction requirements for motor service factor and for converter-fed variable-speed motors (see Clause 4);

c) added terminal box and wiring device requirements for universal AC/DC motors, for AC motors rated above 750 V (ac) or of frame size H315 and above, and for standby generators (see Clause 6);

d) added the method for measuring earthing resistance on small power motors (see 9.11);

e) revised the internal wiring clauses, adding a minimum cross-section for motor leads and stating that the rated voltage of a lead shall not be lower than the maximum working voltage at its location (see Clause 12; Clause 13 of the 2013 edition);

f) revised the temperature limits for materials supporting live parts and for insulating bushing materials, and added thermal class 200 (N) (see Table 7; Table 6 of the 2013 edition);

g) revised the high-frequency impulse endurance requirements, the test method and the specimen requirements under electrical insulation (see 14.4; 15.5 of the 2013 edition);

h) revised the insulation system test requirements, adding qualification tests for type I and type II insulation systems and the marking of the impulse voltage insulation class (IVIC) (see Clause 15; Clause 16 of the 2013 edition);

i) added thermal test requirements for motors fitted with brake coils or controllers, for special-purpose motors and for converter-fed variable-speed motors, and the rule that where the product standard specifies otherwise, that standard governs (see Clause 20);

j) revised the range of DC voltages applied when measuring insulation resistance (see Table 18; Table 16 of the 2013 edition);

k) revised the trip current of the over-current relay on the high-voltage transformer during the power-frequency withstand voltage test (see 23.2.12; 24.2.11 of the 2013 edition);

l) revised the permitted relative displacement between the cord and the clamping position after the static pull test on the supply cord clamping device (see 24.8; 25.8 of the 2013 edition);

m) added the requirement that an integrated drive-and-control motor system shall also comply with GB/T 4208 (see Clause 25);

n) added the steady-state damp heat test method, together with requirements for touch current measurement and related safety verification after the damp heat test (see Clause 26).

Attention is drawn to the possibility that some elements of this document may be the subject of patent rights. The issuing body shall not be held responsible for identifying patents.

This document was proposed by the China Electrical Equipment Industry Association, and is under the jurisdiction of the National Technical Committee on Rotating Machinery of Standardization Administration of China (SAC/TC 26).

The successive editions of this document and of the documents it replaces are: first issued in 1993 as GB 14711-1993; first revised in 2006; second revised in 2013 as GB/T 14711-2013; this is the third revision.

1 Scope

This document specifies general safety requirements for small and medium size rotating electrical machines (motors and generators, hereinafter referred to as "motors") that comply with GB/T 755.

This document applies to activities related to the design, manufacture, inspection, and operation of small and medium size rotating electrical machines. Other types of electrical machines can also be implemented as a reference.

2 Normative references

The provisions in the following documents become essential provisions of this document through reference. For dated references, only the version with the date indicated applies; for undated references, the latest version (including all amendments) applies.

GB/T 755 Rotating electrical machines — Rating and performance · GB/T 825 Eyebolts · GB/T 1971 Rotating electrical machines — Terminal markings and direction of rotation · GB/T 2423.3 Environmental testing — Part 2: Test methods — Test Cab: Damp heat, steady state · GB/T 2423.4 Environmental testing — Part 2: Test methods — Test Db: Damp heat, cyclic (12 h + 12 h) · GB/T 2900.1-2008 Electrotechnical terminology — Fundamental terms · GB/T 2900.18-2008 Electrotechnical terminology — Low-voltage apparatus · GB/T 2900.25 Electrotechnical terminology — Rotating machines · GB/T 4074.7-2024 Methods of test for winding wires — Part 7: Temperature index of enamelled winding wires · GB/T 4207 Determination of the proof and comparative tracking indices of solid insulating materials · GB/T 4208 Degrees of protection provided by enclosure (IP code) · GB/T 4942 Degrees of protection provided by the integral design of rotating electrical machines (IP code) · GB/T 5169.11 Fire hazard testing — Part 11: Glow-wire flammability test method for end-products (GWEPT) · GB/T 5169.12 Fire hazard testing — Part 12: Glow-wire flammability index (GWFI) test method for materials · GB/T 5169.16 Fire hazard testing — Part 16: Test flames — 50 W horizontal and vertical flame test methods · GB/T 5169.21 Fire hazard testing — Part 21: Abnormal heat — Ball pressure test method · GB/T 8170 Rules of rounding off for numerical values and expression and judgement of limiting values · GB/T 11026.4-2012 Electrical insulating materials — Thermal endurance — Part 4: Ageing ovens — Single-chamber ovens · GB/T 12113-2023 Methods of measurement of touch current and protective conductor current · GB/T 12665 Damp heat test requirements for electrical machines used under general environmental conditions · GB/T 13002 Rotating electrical machines — Thermal protection · GB/T 16422.2 Plastics — Methods of exposure to laboratory light sources — Part 2: Xenon-arc lamps · GB/T 17948.1-2018 Functional evaluation of insulation systems — Random-wound windings — Thermal evaluation and classification · GB/T 17948.2 Functional evaluation of insulation systems — Random-wound windings — Changes and substitution of components · GB/T 17948.3 Functional evaluation of insulation systems — Form-wound windings — Thermal evaluation and classification · GB/T 17948.4 Functional evaluation of insulation systems (type II) — Form-wound windings — Electrical endurance · GB/T 20111.3 Electrical insulation systems — Thermal evaluation — Part 3: Encapsulated-coil models — Random-wound EIS · GB/T 20139.1-2016 Electrical insulation systems — Thermal evaluation of modifications to an established EIS — Part 1: Random-wound EIS · GB/T 20139.2-2017 Electrical insulation systems — Thermal evaluation of modifications to an established EIS — Part 2: Form-wound EIS · GB/T 21707 Insulation specification for converter-fed variable-speed motors · GB/T 22714 Test specification for interturn insulation of form-wound windings of low-voltage AC machines · GB/T 22716 Test specification for interturn insulation of DC machine armature windings · GB/T 22718 Method for evaluating the thermal endurance of insulation systems of high-voltage machines · GB/T 22719.1 Interturn insulation of random-wound windings of low-voltage AC machines — Part 1: Test methods · GB/T 22719.2 Interturn insulation of random-wound windings of low-voltage AC machines — Part 2: Test limits · GB/T 22720.1-2017 Qualification and quality control tests for partial-discharge-free (type I) insulation systems in converter-fed machines · GB/T 22720.2-2019 Qualification tests for partial-discharge-resistant (type II) insulation systems in converter-fed machines

3 Terms and definitions

For the purposes of this document, the terms and definitions given in GB/T 755 and GB/T 2900.1-2008 apply, together with those set out in this clause. Insulating materials are grouped by comparative tracking index: group IIIa covers 175 ≤ CTI < 400, group IIIb covers 100 ≤ CTI < 175. [SOURCE: GB/T 16935.1-2023, 5.3.2.4, modified]

4 Marking and description

4.1 Each motor shall carry one or more nameplates of durable material, securely attached and permanently mounted where they remain clearly visible on the frame or housing, in accordance with GB/T 755.

4.2 Where applicable, the nameplate shall be permanently marked with the items required by GB/T 755. These items need not all appear on the same nameplate, and additional manufacturer information need not be marked.

4.3 Except for routine maintenance, a repaired or refurbished motor shall carry an auxiliary nameplate stating the repair contractor, the year of repair and the details of the changes.

4.4 Motors designed for a single direction of rotation shall show that direction with an arrow. The arrow need not be on the nameplate but shall be readily visible.

4.5 A motor with a dedicated neutral terminal shall have it marked with the letter "N".

4.6 The protective earthing symbol shall be marked near the protective earthing terminal, with the letters "PE" added where necessary. These markings shall not be placed on screws, removable washers or removable components used to connect conductors.

4.7 Where the protective earthing cord uses an insulated sheathed wire, it shall be green and yellow. This colour combination is prohibited for any non-earthing cord.

4.8 Terminal markings, direction of rotation, and the relationship between the two shall comply with GB/T 1971.

4.9 Where a capacitor is fitted, its parameters — capacitance and rated voltage — shall be clearly indicated.

4.10 For series motors, and for compound motors whose speed regulation exceeds 35 %, the manufacturer shall specify the maximum safe operating speed and mark it on the nameplate. For DC motors able to withstand the no-load speed at 1.1 times rated voltage, the maximum safe operating speed need not be marked.

4.11 Where the service factor of the motor is greater than 1, the actual service factor shall be marked.

4.12 Additional marking requirements for converter-fed variable-speed motors: a) the application type, for example “converter duty machine”; b) the speed range the motor is designed for, or — where the nominal speed at nominal frequency is marked — the frequency range; c) the torque type the motor is designed for, for example VT (variable torque), CT (constant torque), CHp (constant power) or an equivalent mode; d) the type of converter the motor is to be used with, for example VSI or VVI (voltage-source), CSI (current-source), VPWM, CPWM, LCI or a cycloconverter; e) for a motor with a type I insulation system to GB/T 22720.1-2017 designed for voltage-source converter supply, the manufacturer shall state the impulse voltage insulation class (IVIC) in the documentation and, where practicable, on the nameplate.

4.13 Where a motor carries lifting devices intended only for lifting motor components, this shall be clearly marked, unless the device can safely lift the complete motor. The warning shall read: “This lifting device is not for lifting the complete motor; only the component attached to it may be safely lifted”, or words to that effect.

4.14 The following additional information and instructions shall be provided. Where the motor forms part of a final assembly and the motor connection information appears in the connection diagram or the instructions of the final equipment, or both, the diagrams and installation instructions under a) and b) need not accompany each motor. a) The motor shall carry a terminal marking diagram whose markings agree with those on the motor terminals, fixed so that it cannot come off. b) Installation instructions shall cover drainage, mounting, bearing lubrication and similar structural requirements, and shall include the devices supplied, such as heaters and winding thermal protectors.

4.15 The date of manufacture shall be marked on each motor where it can be read without tools, by date code, serial number or an equivalent method.

4.16 Markings may be printed, engraved, pressed or applied by any other effective method. Material and method shall keep the marking clear and durable, without fading or detaching, for the whole normal operating life of the motor.

4.17 Compliance is checked by visual inspection and by the marking test: rubbing for 15 s with a cotton cloth dampened with water, then for 15 s with a cloth dampened with petrol, one reciprocating stroke per second at about 2 N/cm². After this test and every other test in the document the markings shall remain legible, and shall not be easily removed, displaced or curled.

5 Frame and housing

5.1.1 Every component of the housing shall withstand the temperatures and mechanical stresses that arise in normal operation, without becoming a fire or shock hazard through bending, creepage or deformation.

5.1.2 Where a drain hole is required, the motor shall have adequate drainage to stop water accumulating inside and reducing clearances and creepage distances between windings and exposed live parts. Ventilation holes may serve as drain holes. Drain holes shall comply with GB/T 4942.

5.1.3 Where the motor is an integral part of other equipment, the functions of frame, housing and terminal box may be provided by the structure of that equipment.

5.1.4 Naturally air-cooled motors requiring built-in overheat protection shall be protected in accordance with GB/T 13002.

5.1.5 Except for open-type motors, panels or covers giving access to exposed live parts above 36 V AC or 50 V DC shall open only with a tool or key.

5.2.1 The structural design shall provide adequate strength. Non-metallic housings shall also be heat-resistant, flame-retardant and corrosion-resistant.

5.2.2 Non-metallic housings and fan covers shall withstand temperature exposure under normal and abnormal operation and shall pass the impact test of 24.3 — unless the motor is to be installed inside the housing of other equipment, in which case that test does not apply. Non-metallic housings shall also meet the flame test of 18.2.

5.2.3 Housing protection shall be classified according to GB/T 4942 and clearly specified in the product standard; compliance is determined by testing to the same standard.

6 Terminal box and wiring devices

6.1.1 For motors rated 750 V and below, the terminal box may be a separate component mounted outside the motor, or may form part of the housing.

6.1.2 A metal terminal box shall have the thickness given in Table 1 and shall meet the test of 24.4.

6.1.4 A motor fitted with a terminal box shall have a removable inspection panel or cover, and no power connections shall be made on such panels or covers.

6.2.1 For AC motors rated above 750 V or of frame size H315 and above, the power terminal box may be provided separately, provided it sits at ground level, on a mezzanine or in a catwalk; is no more than 5 m from the motor in any direction; and gives acceptable access for connecting the motor leads.

6.2.3 For motors above 750 V, auxiliary leads shall terminate in the terminal box or in a separate one. Leads from auxiliary items normally operating at 30 V (rms) and below shall be separated from other auxiliary leads by suitable partitions, or terminated in a separate box.

6.5.1 For standby generators rated 750 V and below, the terminal box panel or enclosure shall be flame-retardant, moisture-proof and oil-resistant; if metal, of the thickness given in Table 1, and shall pass the static pressure test of 24.4.

6.5.4 Where conduit entries are provided they shall be no smaller than the size corresponding to the full-load current given in Table 2, and shall sit on a flat area large enough for the required bushings or locknuts.

6.5.5 The method of securing the terminal block shall be independent of the method of securing the cover plate.

7 Conduit bushings and equivalent threaded openings

7.1 Conduit screw holes may be sealed with straight or tapered pipe threads of no less than 3.5 pitches. The number of infeed holes shall be specified in the product standard. Wire infeed holes shall be fitted with insulating sleeves and sealed with rubber or similar material on despatch.

7.2 Conduit bushings not integrally moulded with the metal housing, and threaded openings for rigid metal conduit, shall have adequate mechanical strength, determined by the test of 24.5.

8 Mechanical assembly

8.1 The motor shall be assembled so that vibration in normal operation causes no harmful effect. Brush covers shall be tightened or otherwise prevented from loosening.

8.2 Uninsulated live parts shall be secured against rotation or displacement wherever movement would bring clearances and creepage distances below the minimum allowed.

8.3 Friction between mating surfaces is not accepted as the sole means of preventing movement of live parts; suitable lock washers are.

8.6 Lifting rings and similar devices shall have sufficient mechanical strength to resist permanent deformation or rotation under the axial proof load. The test method follows GB/T 825.

9 Grounding

9.1 The motor shall have a protective earthing device complying with GB/T 755.

9.2 There shall be a permanent, reliable electrical connection between frame and protective earthing device, which shall stay connected when the motor is moved on its base.

9.4 The protective earthing connection shall be locked against accidental rotation and against any reduction of clearances and creepage distances, and shall not be loosenable without tools.

9.5 The protective earthing terminal shall serve no purpose other than protective earthing.

9.8 The connection shall penetrate non-conductive coatings such as paint. Cold crimping or equivalent means are acceptable; hinged joints and soldering alone are not.

9.9 Earthing conductors passing through elastic rubber bases shall be metal; conductive rubber shall not be used for earthing.

9.11 The resistance of the earthing path shall not exceed 0.1 Ω, measured by passing 1.5 times rated current or 25 A — whichever is greater — between the intended earthing component and the earthing terminal, then dividing the measured voltage drop by the current.

10 Flexible supply cord

10.1 Where a flexible supply cord is fitted, and where a plug is provided for connection to the supply circuit, cord and plug shall meet the relevant product standards.

10.2 Unless earthing is not required, these cords shall include an earthing conductor, and should be colour-coded or marked for easy identification.

10.3 The rated voltage of the cord shall be no less than the maximum operating voltage of the motor, and its current-carrying capacity at least equal to the service-factor load current or 125 % of full-load rated current, whichever is greater.

10.4 Unless tensile force is eliminated by other means, an insulating protective layer and a clamping device shall be fitted at the cord outlet, so that external pull is not transmitted to the internal wiring.

11 Clearances and creepage distances

11.1.2 For stationary parts of brushed motors — brush holders and the commutator and slip-ring areas — clearances and creepage distances shall be increased by at least 50 % to allow for carbon dust deposits, unless suitable spacers or collars are fitted.

11.1.3 The increased requirement does not apply to motors of frame size above 90.

11.1.5 Wire connectors, including quick-connect types, shall be prevented from rotating or moving in a way that reduces clearances below 11.1.1 — unless rotating the connector 30° either way leaves them unchanged, or the connector screw is insulated.

11.1.6 Clearances may be achieved with insulating barriers: heat- and moisture-resistant materials where live parts may touch the barrier; moisture-resistant fibre no thinner than 0.66 mm elsewhere, or 0.33 mm where clearances exceed half the specified values.

11.2.1 For motors rated 1000 V and above, clearances and creepage distances between live parts of different polarity in a terminal box, and between live parts and non-current-carrying metal or removable enclosures, shall be no less than the values in Table 5.

· · · · · · This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 50 pages — is available in the English PDF.