GB/T 14711-2025 PDF English
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General requirements for safety of small and medium size rotating electrical machines
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| GB 14711-2013 | English | 125 |
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[GB/T 14711-2013] General requirements for safety of small and medium size rotating electrical machines
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Safety requirements of small and medium size rotating electrical machines
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General requirements for safety of small and medium size rotating electrical machines
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GB/T 14711-2025: General requirements for safety of small and medium size rotating electrical machines
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT14711-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.160.01
CCS K 20
Replacing GB/T 14711-2013
General Requirements for Safety of Small and Medium Size
Rotating Electrical Machines
Issued on: MAY 30, 2025
Implemented on: DECEMBER 1, 2025
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 4
1 Scope... 7
2 Normative References... 7
3 Terms and Definitions... 9
4 Marking and Description... 13
5 Frame and Housing... 15
6 Terminal Box and Wiring Devices... 16
7 Conduit Bushings and Equivalent Threaded Openings... 19
8 Mechanical Assembly... 19
9 Grounding... 20
10 Flexible Supply Cord... 21
11 Clearances and Creepage Distances... 22
12 Internal Wiring... 25
13 Connectors... 27
14 Electrical Insulation... 27
15 Insulation Structure... 30
16 Brush Holders and Terminals... 32
17 Wiring Terminals... 32
18 Non-Metallic Functional Components... 35
19 Rated Tests... 36
20 Thermal Test... 38
21 Touch Current... 40
22 Insulation Resistance... 42
23 Dielectric Strength Test... 43
24 Mechanical Strength Test... 46
25 Protection Test... 48
26 Damp Heat Test... 48
27 Corrosion Protection... 49
28 Components... 49
29 Electromagnetic Compatibility (EMC)... 50
General Requirements for Safety of Small and Medium Size
Rotating Electrical Machines
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 following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
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.Testing method - Test Cab. Damp heat, steady
state
GB/T 2423.4 Environmental testing for electric and electronic products - Part 2.Test
methods - Test Db. Damp heat, cyclic (12h+12h cycle)
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 electrical machines
GB/T 4074.7-2024 Test methods of winding wires - Part 7.Test method for determining
the temperature index of enameled winding wire, according to the Chinese standard
GB/T 17948.3 Rotating electrical machines - Functional evaluation of insulation systems
- Test procedures for form-wound windings - Thermal evaluation and classification of
insulation systems used in rotating machines
GB/T 17948.4 Rotating electrical machines - Functional evaluation of formed windings -
Test procedure for voltage endurance evaluation (II type)
GB/T 20111.3 Electrical insulation systems - Procedures for thermal evaluation - Part 3.
Specific requirements for encapsulated–coil model - Wire–wound electrical insulation
system (EIS)
GB/T 20139.1-2016 Electrical insulation systems - Thermal evaluation of adjusted
electrical insulation systems (EIS) - Part 1.Random-wound EIS
GB/T 20139.2-2017 Electrical insulation systems - Thermal evaluation of modifications
to an established electrical insulation system (EIS) - Part 2.Form-wound EIS
GB/T 21707 Insulation specification for variable frequency adjustable speed definite
purpose converter-fed three-phase induction motors
GB/T 22714 Test specifications of interturn insulation of form-wound winding for AC low-
voltage electrical machines
GB/T 22716 Test specifications of interturn insulation of armature winding for DC
electrical machines
GB/T 22718 Thermal evaluation methods of insulation systems for high-voltage electrical
machines
GB/T 22719.1 Interturn insulation of random-wound winding for AC low-voltage
electrical machines - Part 1.Test methods
GB/T 22719.2 Interturn insulation of random-wound winding for AC low-voltage
electrical machines - Part 2.Test limits
GB/T 22720.1-2017 Rotating electrical machines - Qualification and quality control tests
of partial discharge free electrical insulation systems (Type I) used in rotating electrical
machines fed from voltage converters
GB/T 22720.2-2019 Rotating electrical machines - Qualification tests for the partial
discharge resistant electrical insulation systems (Type II) used in rotating electrical
machines fed from voltage converters
3 Terms and Definitions
For the purposes of this Document, the terms and definitions given in GB/T 755, GB/T 2900.1-
--- Insulating Material Group IIIa. 175 ≤ CTI < 400;
--- Insulating Material Group IIIb. 100 ≤ CTI < 175.
[SOURCE. GB/T 16935.1-2023, 5.3.2.4, modified]
4 Marking and Description
4.1 Each motor shall have one or more nameplates made of durable material, securely attached
to the motor, in accordance with the requirements of GB/T 755.All nameplates shall be
permanently or equivalently mounted in a clearly visible location on the motor frame or housing,
depending on the motor's construction and mounting type.
4.2 Where applicable, the motor nameplate shall be permanently marked with the
corresponding items in accordance with the requirements of GB/T 755.These items do not need
to be all on the same nameplate. If the manufacturer provides additional information, it need
not be marked on the nameplate.
4.3 Except for routine maintenance, when a motor is repaired or refurbished, an auxiliary
nameplate shall be provided to indicate the name of the repair contractor, the year of repair, and
the details of the changes.
4.4 For motors designed for single-direction rotation, the direction of rotation shall be indicated
by an arrow. The arrow need not be marked on the nameplate, but it shall be readily visible.
4.5 If the motor has a dedicated terminal for the neutral conductor, it shall be marked with the
letter "N."
4.6 The protective earthing symbol " " shall be marked near the motor's protective earthing
terminal; and the letter "PE" shall be applied, if necessary. These markings shall not be placed
on screws, removable washers, or removable components used to connect conductors. For
motors where the yellow-green grounding wire cannot be removed without damaging the motor,
the protective earthing symbol " " may not be marked near the motor's protective earthing
terminal.
4.7 When the protective grounding cord uses an insulated sheathed wire, it shall be green and
yellow. This color marking is prohibited for non-grounding cords.
4.8 The motor terminal markings, direction of rotation, and the relationship between the
direction of rotation and the terminal markings shall comply with the provisions of GB/T 1971.
4.9 If the motor is equipped with a capacitor, the capacitor's parameters (e.g., capacitance and
rated voltage) shall be clearly indicated.
4.10 For series-wound motors and compound-wound motors with a speed adjustment greater
provided components, such as heaters and winding thermal protectors, etc.
4.15 The date of manufacture shall be marked on each motor in a location that is easily visible
without the use of any tools. This may be done by a date code, serial number, or similar marking
method.
4.16 All markings on the motor may be made by printing, engraving, pressing, or other effective
marking methods. The marking material and marking method shall ensure that the marking is
clear and durable and shall not fade or fall off throughout the normal operating life of the motor.
4.17 Whether the marking meets the requirements shall be determined by visual inspection and
testing according to the marking test method.
a) Visual inspection and rubbing the marking with a cotton cloth dampened with water for
15 s, then rubbing with a cotton cloth dampened with gasoline for 15 s, with one
reciprocating rub per second. During the test, a pressure of approximately 2 N/cm² shall
be applied to the cotton cloth to press against the marking.
b) The motor markings must remain legible after the above tests and all tests specified in
this Document. They must not be easily removed, movable, or curled.
5 Frame and Housing
5.1 General
5.1.1 The material of any component on the motor housing must be able to withstand the high
temperatures and mechanical stresses that may occur during normal operation and must not
present a fire or electric shock hazard due to bending, creepage, or deformation.
5.1.2 If a motor requires a drain hole, except for motors that cannot be intruded by water (e.g.,
motors intended for use in water) or where water cannot accumulate internally during use, the
motor must have appropriate drainage measures to prevent water from accumulating internally
and reducing the clearances and creepage distances between the windings and exposed live
parts against ground. The motor's ventilation holes may also serve as drain holes. When drain
holes are provided on a motor, they must comply with the provisions of GB/T 4942.
5.1.3 If the motor is an integral component of other equipment, the functions of the motor frame,
housing, and terminal box may be provided by the structure of the equipment.
5.1.4 For naturally air-cooled motors, if built-in overheat protection is required, thermal
protection shall be provided in accordance with GB/T 13002.
5.1.5 Except for open-type motors, to prevent access to exposed live parts exceeding 36V AC
or 50V DC, ensure that panels or covers can only be opened with a tool or key.
5.2 Motor housing
5.2.1 The motor's structural design shall provide adequate strength. For motors with non-
metallic housings, they shall also be heat-resistant, flame-retardant, and corrosion-resistant.
5.2.2 If the motor housing and fan cover are made of non-metallic materials, they shall be able
to withstand the adverse effects of temperature exposure under normal and abnormal operating
conditions and shall meet the impact test requirements of 24.3; unless the motor shall be
installed in the housing of other equipment, in which case, this test does not apply. If the motor
housing is made of non-metallic materials, it shall also meet the applicable flame test
requirements of 18.2.
5.2.3 The motor shall have adequate housing protection. The housing protection level shall be
classified according to GB/T 4942 and shall be clearly specified in the product standard.
Whether meeting the requirements shall be determined through testing and inspection in
accordance with GB/T 4942.
6 Terminal Box and Wiring Devices
6.1 Requirements for motors 750 V and below
6.1.1 The motor’s terminal box may be a separate component mounted on the outside of the
motor, or it may be partially or entirely part of the motor housing.
6.1.2 If the terminal box is made of metal, its thickness shall comply with the provisions of
Table 1 and meet the requirements of test in 24.4.
6.1.3 Terminal boxes made of non-metallic materials shall comply with the provisions of Clause
18.
6.1.4 When a motor is equipped with a terminal box, it shall be provided with a removable
inspection panel or cover. No power connections shall be made on such panels or covers.
6.2 AC Motors with a rated voltage of 750 V (AC) or more or frame sizes H315 and above
6.2.1 The motor power terminal box may be provided separately, provided that.
a) the terminal box is located at ground level, on a mezzanine, or in a catwalk;
b) the terminal box is not removed from the motor by more than 5 m in any horizontal or
vertical direction;
c) acceptable access is provided for connecting the motor leads.
6.2.2 The terminal box described in 6.2.1 shall be marked in accordance with the requirements
of Clause 4.
6.2.3 For motors with a rated voltage exceeding 750 V, auxiliary leads (except the secondary
connections of current transformers and voltage transformers located in the motor terminal
housing and separated from the motor leads by suitable partitions) shall be terminated in the
terminal box or in a terminal box separate from the motor terminals. 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 terminal box.
6.3 DC Motors and AC Motors (including DC/AC Motors) up to frame size H80
Device connections to the power conductors, such as thermal protectors, switches, and relays,
may be mounted on the terminal box (or wiring compartment) cover. These connections, if
provided, are to be wired by the manufacturer.
6.4 DC motors of frame size H90 and above
If a terminal box is provided, it shall comply with the provisions of this Clause.
6.5 Standby generators (750 V and below)
6.5.1 The terminal box panel or enclosure shall be made of flame-retardant, moisture-proof,
and oil-resistant materials. If made of metal, its thickness shall comply with the provisions of
Table 1.The terminal box panel or enclosure shall meet the requirements of the static pressure
test in 24.4.
6.5.2 Terminal box panels or enclosures made of non-metallic materials shall meet the
requirements of the flame test in 18.2 and the impact test in 24.3.
6.5.3 Standby generators, if provided with a terminal box panel or enclosure, shall be equipped
with removable access panels or covers that do not provide power connections.
6.5.4 For standby generators, if conduit entries are provided, they shall be no smaller than the
size corresponding to the full-load current of the motor as specified in Table 2.
Conduit entries shall be located on a surface with a sufficiently large flat area to accommodate
the required bushings or locknuts, unless the conduit entry is suitably threaded and the bushing
is not required to protect the insulation of the supply conductors entering the terminal box.
Generators requiring commercially available conduit larger than 41 mm may omit the conduit
opening so that the required power conductor entry opening can be machined during installation.
Caution. This subclause does not consider insulated bonding conductors and grounding
conductors; these may require larger terminal boxes or conduit entries.
6.5.5 The method for securing the terminal block shall be independent of the method for
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, with a threaded
length of no less than 3.5 pitches. The number of infeed screw holes shall be specified in the
product standard. Wire infeed holes shall be equipped with insulating sleeves and sealed with
rubber or similar material when leaving the factory.
7.2 Conduit bushings in terminal boxes that are not integrally molded with the metal housing,
or threaded conduit openings for rigid metal conduit, shall have adequate mechanical strength.
This shall be determined by testing in accordance with 24.5.
8 Mechanical Assembly
8.1 The motor shall be assembled so that vibrations during normal operation shall not cause
any harmful effects. Brush covers shall be tightened or otherwise prevented from loosening.
8.2 Uninsulated live parts shall be secured to the baseplate or mounting surface to prevent
rotation or displacement if movement should cause clearances and creepage distances to fall
below the minimum allowable values.
8.3 Friction between mating surfaces is not permitted as the sole means of preventing movement
or rotation of live parts, but the use of suitable lock washers for this purpose is acceptable.
8.4 Switches, motor connecting plugs, plug sockets, or similar components shall be securely
mounted and prevented from rotating.
8.5 Suitable lock washers may be used to prevent rotation of small welding handle-mounted
switches or other switches that are mounted using only a single hole.
8.6 Lifting rings or similar devices of the motors and their components used to lift shall have
sufficient mechanical strength to prevent permanent deformation or rotation due to the load
during the axial proof load test. The test method for lifting rings allowing axial proof loads shall
comply with the provisions of GB/T 825.
9 Grounding
9.1 The motor shall have a protective grounding device that complies with the provisions of
GB/T 755.
9.2 There shall be a permanent, reliable, and good electrical connection between the motor
frame and the protective grounding device. The protective grounding conductor shall remain
reliably connected when the motor is moved on the equipment base.
9.3 If the motor uses a terminal to connect the grounding conductor, the terminal shall meet the
requirements for terminals in Clause 17.
9.4 The connection of the protective grounding terminal shall be securely locked to prevent
accidental rotation and the reduction of clearance and creepage distances. It shall not be possible
to loosen it without tools.
9.5 The protective grounding terminal shall not be used for any purpose other than protective
grounding.
9.6 The materials of the protective grounding conductor, the protective grounding terminal, and
its connection device shall be compatible; resistant to electrical corrosion; and good electrical
conductors. If ferrous metal is used, it shall be electroplated or otherwise effectively protected
against rust.
9.7 The protective grounding conductor must be sufficiently flexible to withstand motor
vibration stress and must be appropriately protected to prevent hazards during motor operation
and installation.
9.8 The protective grounding connection must ensure reliable penetration through non-
conductive coatings such as paint. Connections may be made by cold crimping or other
equivalent means; hinged joints and soldering alone shall not be used.
9.9 Grounding conductors penetrating elastic rubber bases must be metal; conductive rubber
must not be used for grounding.
9.10 The screw and grounding conductor of the protective grounding terminal must have
sufficient cross-section. The minimum nominal diameter of the protective grounding screw is
shown in Table 3.The cross-sectional area of the grounding conductor must comply with the
provisions of GB/T 755.
9.11 The resistance of the grounding path shall not exceed 0.1Ω. This resistance is determined
as follows. For small power motors, a current equal to 1.5 times the motor's rated current or
25A (whichever is greater) is applied between the intended grounding component and the
grounding conductor terminal. This current is then passed alternately between the grounding
terminal or grounding contact and an accessible grounded metal part. The voltage drop is
measured and divided by the current flowing through the circuit to calculate the grounding path
resistance. For motors with a rated power exceeding that of small power motors, the above-
mentioned current value is 25A or the motor's rated current, whichever is greater.
9.12 The grounding device shall bear the grounding marking specified in 4.6.
10 Flexible Supply Cord
10.1 If the motor is provided with a flexible supply cord, or if a flexible supply cord extending
outside the motor frame (housing) is provided to facilitate connection to other equipment, and
if necessary, a plug for connection to the power supply circuit is provided, such cord and plug
shall meet the requirements of the relevant standards for such product or the requirements for
cords in the relevant standards for such type of equipment.
10.2 Unless grounding is not required, these flexible cords shall include a grounding conductor.
The flexible supply cords (including terminals) should be color-coded or marked for easy
identification.
10.3 The rated voltage of the flexible supply cord shall be no less than the maximum operating
voltage of the motor; and its current-carrying capacity shall be at least equal to the load current
of the service factor or 125% of the full-load rated current, whichever is greater. The cord
insulation shall be able to withstand the power frequency withstand voltage test for the circuit.
10.4 Unless other measures are taken to eliminate potential tensile forces, or the flexible supply
cord is not exposed to the motor, an insulating protective layer and a clamping device shall be
provided at the flexible supply cord outlet to prevent external tensile forces from being
transmitted to the internal wiring and to prevent the flexible supply cord from rotating or
shifting and causing accidents.
11.1.2 For stationary parts (e.g., brush holders) of brushed motors only, clearances and creepage
distances in the commutator and slip ring areas shall be increased by at least 50% due to carbon
dust deposits (e.g., on brush holder insulation). Otherwise, suitable spacers, collars, or similar
components shall be provided.
11.1.3 The specified increased clearance and creepage distance requirements do not apply to
motors with frame sizes greater than 90.
11.1.4 For rotor windings and centrifugal switches of wound-rotor motors, clearances and
creepage distances may be less than those specified in Table 4.However, this shall not result in
hazardous consequences.
11.1.5 Wire connectors, including pressure-type connectors (quick-connect types), shall be
prevented from rotating or moving in a manner that shall reduce clearances and creepage
distances below those specified in 11.1.1.Unless when the connector is rotated 30° left or right,
the clearances and creepage distances remain unchanged; or when the connector screw is
insulated, measures to prevent connector rotation may be omitted.
11.1.6 The clearances and creepage distances specified in Table 4 may be achieved by using
insulating barriers. Such barriers shall be made of the materials specified below.
a) If exposed live parts are within or could come into contact with the insulating barrier,
heat-resistant and moisture-resistant materials (e.g., porcelain bottle, phenolic plastic,
polyester, carbonated polyester, nylon, mica, etc.) shall be used.
b) Suitable moisture-resistant fiber and similar hygroscopic material barriers may be used
in locations that do not come into contact with exposed live parts (except magnet wire).
Their thickness shall be no less than 0.66 mm. If the clearances and creepage distances
exceed half of the specified values, insulating barriers with a thickness of no less than
0.33 mm may be used. Other insulating materials with a thickness less than 0.33 mm
(e.g., pure mica with a thickness of no less than 0.25 mm) may be used if they are tested
and found to have mechanical and electrical properties sufficient to meet all normal
operating conditions.
11.2 Clearances and creepage distances for motors with rated voltages of 1000 v and above
11.2.1 Clearances and creepage distances between different live parts or between parts with
different polarity exposed in a terminal box, and between exposed live parts (including magnet
wire) and non-current-carrying metal or removable metal enclosures, shall be no less than those
specified in Table 5.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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