GB/T 755-2025 Rotating electrical machines - Rating and performance
1 Scope
This document is applicable to all rotating electrical machines, except rotating electrical machines for rail and road vehicles, which are covered by the IEC 60349 series of standards.
Machines within the scope of this document may also be subject to superseding, modifying or additional requirements in other standards, for example, IEC 60079 and IEC 60092.
Note: If particular clauses of this document are modified to meet special applications, for example machines subject to radioactivity or machines for aerospace, all other clauses apply insofar as they are compatible.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 21210-2016 Starting performance of single-speed three-phase cage induction motors (IEC 60034-12:2016, IDT)
IEC 60027-1 Letter symbols to be used in electrical technology - Part 1 : General
Note: GB/T 2987-1996 Letter symbols of parameter for electronic tubes (IEC 60027-1:1992, NEQ)
IEC 60027-4 Letter symbols to be used in electrical technology - Part 4:Rotating electric machines
IEC 60034-2 (All parts) Rotating electrical machines - Part 2:Standard methods for determining losses and efficiency from tests (excluding machines for traction vehicles)
IEC 60034-3 Rotating electrical machines - Part 3:Specific requirements for synchronous generators driven by steam turbines or combustion gas turbines
IEC 60034-5 [Rotating electrical machines - Part 5:Degrees of protection provided by the integral design of rotating electrical ma- chines(IP code) - Classification]
Note: GB/T 4942-2021 Degrees of protection provided by the integral design of rotating electrical machines (IP code) - Classification (IEC 60034-5:2020, IDT)
IEC 60034-6 Rotating electrical machines - Part 6: Methods of cooling(IC code)
Note: GB/T 1993-1993 Cooling methods for rotating electrical machines (IEC 60034-6:1991, IDT)
IEC 60034-8 Rotating electrical machines - Part 8:Terminal markings and direction of Rotation
Note: GB/T 1971-2021 Rotating electrical machines - Terminal markings and direction of rotation (IEC 60034-8:2014, IDT)
IEC 60034-12 Rotating electrical machines - Part 12:Starting performance of single-speed three-phase cage induction motors
Note: GB/T 21210-2016 Starting performance of single-speed three-phase cage induction motors (IEC 60034-12:2016, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-411 and the following apply.
Note 1: For definitions concerning cooling and coolants, other than those in 3.17 to 3.22, see IEC 60034-6.
Note 2: For the purposes of this document, the term “agreement” means “agreement between the manufacturer and purchaser’.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
- IEC Electropedia: available at http://www.electropedia.org/;
- ISO online browsing platform: available at http://www.iso.org/obp
3.1
rated value
quantity value assigned, generally by a manufacturer, for a specified operating condition of a machine
Note: The rated voltage or voltage range is the rated voltage or voltage range between lines at the terminals.
[Source: GB/T 2900.25-2008, 411-51-23]
3.2
rating
set of rated values and operating conditions
[Source: GB/T 2900.25-2008, 411-51-24]
3.3
rated output
value of the output included in the rating
3.4
load
all the values of the, in case of a generator, electrical and, in case of a motor, mechanical quantities that signify the demand made on a rotating machine by an electrical circuit or a mechanism at a given instant
[Source: GB/T 2900.25-2008, 411-51-01, modified]
3.5
no-load (operation)
state of a machine rotating with zero output power (but under otherwise normal operating conditions)
[Source: GB/T 2900.25-2008, 411-51-02, modified]
3.6
full load
load which causes a machine to operate at its rating
[Source: GB/T 2900.25-2008, 411-51-10]
3.7
full load value
quantity value for a machine operating at full load
[Source: GB/T 2900.25-2008, 411-51-11]
Note: This concept applies to power, torque, current, speed, etc.
3.8
rest and de-energized
complete absence of all movement and of all electrical supply or mechanical drive
[Source: GB/T 2900.25-2008, 411-51-03]
3.9
duty
statement of the load(s) to which the machine is subjected, including, if applicable, starting, electric braking, no-load and rest and de-energized periods, and including their durations and sequence in time
[Source: GB/T 2900.25-2008, 411-51-06]
3.10
duty type
continuous, short-time or periodic duty, comprising one or more loads remaining constant for the duration specified, or a non-periodic duty in which generally load and speed vary within the permissible operating range
[Source: GB/T 2900.25-2008, 411-51-13]
3.11
cyclic duration factor
ratio between the period of loading, including starting and electric braking, and the duration of the duty cycle, expressed as a percentage
[Source: GB/T 2900.25-2008, 411-51-09]
3.12
locked rotor torque
minimum measured torque the motor develops at its shaft and with the rotor locked, over all its angular positions, at rated voltage and frequency
[Source: GB/T 2900.25-2008, 411-48-06]
3.13
locked rotor current
greatest steady-state r.m.s. current taken from the line with the rotor locked, over all angular positions of its rotor, at rated voltage and frequency
[Source: GB/T 2900.25-2008, 411-48-16]
3.14
pull-up torque (of an a.c. motor)
minimum steady-state asynchronous torque which the motor develops between zero speed and the speed which corresponds to the breakdown torque, when the motor is supplied at the rated voltage and frequency
Note 1: This definition does not apply to those asynchronous motors of which the torque continually decreases with increase in speed.
Note 2: In addition to the steady-state asynchronous torques, harmonic synchronous torques, which are a function of rotor load angle, will be present at specific speeds.
At such speeds, the accelerating torque may be negative for some rotor load angles.
Experience and calculation show this to be an unstable operating condition and therefore harmonic synchronous torques do not prevent motor acceleration and are excluded from this definition.
3.15
breakdown torque (of an a.c. motor)
maximum steady-state asynchronous torque which the motor develops without an abrupt drop in speed, when the motor is supplied at the rated voltage and frequency
Note: This definition does not apply to asynchronous motors with torques that continually decrease with increase in speed.
3.16
pull-out torque (of a synchronous motor)
maximum torque which the synchronous motor develops at synchronous speed with rated voltage, frequency and field current
3.17
cooling
procedure by means of which heat resulting from losses occurring in a machine is given up to a primary coolant, which may be continuously replaced or may itself be cooled by a secondary coolant in a heat exchanger
[Source: GB/T 2900.25-2008, 411-44-01]
3.18
coolant
medium, liquid or gas, by means of which heat is transferred
[Source: GB/T 2900.25-2008, 411-44-02]
3.19
primary coolant
medium, liquid or gas, which, being at a lower temperature than a part of a machine and in contact with it, removes heat from that part
[Source: GB/T 2900.25-2008, 411-44-03]
3.20
secondary coolant
medium, liquid or gas, which, being at a lower temperature than the primary coolant, removes the heat given up by this primary coolant by means of a heat exchanger or through the external surface of the machine
[Source: GB/T 2900.25-2008, 411-44-04]
3.21
direct cooled (inner cooled) winding
winding mainly cooled by coolant flowing in direct contact with the cooled part through hollow conductors, tubes, ducts or channels which, regardless of their orientation, form an integral part of the winding inside the main insulation
Note: In all cases when “indirect” or “direct”’ is not stated, an indirect cooled winding is implied.
[Source: GB/T 2900.25-2008, 411-44-08]
3.22
indirect cooled winding
any winding other than a direct cooled winding
Note: In all cases when “indirect” or “direct” is not stated, an indirect cooled winding is implied.
[Source: GB/T 2900.25-2008, 411-44-09]
3.23
supplementary insulation
independent insulation applied in addition to the main insulation in order to ensure protection against electric shock in the event of failure of the main insulation
3.24
moment of inertia
sum (integral) of the products of the mass elements of a body and the squares of their distances (radii) from a given axis
3.25
thermal equilibrium
state reached when the temperature rises of the heating parts of the machine do not vary by more than a gradient of 1 K per half hour
Note: Thermal equilibrium may be determined from the time-temperature rise plot when the straight lines between points at the beginning and end of two successive intervals of half hour each have a gradient of 1K or less per half hour or 2K or less per hour.
[Source: GB/T 2900.25-2008, 411-51-08, modified]
Contents
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Duty
5 Rating
6 Site conditions
7 Electrical operating conditions
8 Thermal performance and tests
9 Other performance and tests
10 Information requirements
11 Miscellaneous requirements
12 Tolerances
13 Electromagnetic compatibility (EMC)
14 Application requirements
Annex A (informative) Guidance for the application of duty type S10 and for establishing the value of relative thermal life expectancy TL
Annex B (informative) Electromagnetic compatibility (EMC) limits
Bibliography
Figure 1 Continuous running duty – Duty type S1
Figure 2 Short-time duty - Duty type S2
Figure 3 Intermittent periodic duty – Duty type S3
Figure 4 Intermittent periodic duty with starting – Duty type S4
Figure 5 Intermittent periodic duty with electric braking – Duty type S5
Figure 6 Continuous operation periodic duty – Duty type S6
Figure 7 Continuous operation periodic duty with electric braking – Duty type S7
Figure 8 Continuous operation periodic duty with related load/speed changes – Duty type S8
Figure 9 Duty with non-periodic load and speed variations – Duty type S9
Figure 10 Duty with discrete constant loads – Duty type S10
Figure 11 Voltage and frequency limits for motors and for generators except generators or synchronous compensators within the scope of IEC 60034-3 and hydro generators within the scope of IEC 60034-33
Figure 12 Worst case increase in temperature rise (∆θ) and reduction of output power (∆P) of motors as a function of the combined change of voltage and frequency |△φ | indicative guideline to users of motors and generators only
Figure 13 Factor K for determining RPE,M
Table 1 Preferred voltage ratings
Table 2 Unbalanced operating conditions for synchronous machines
Table 3 CCC symbol designation
Table 4 Primary functions of machines
Table 5 Reference coolant (see also Table 11)
Table 6 Time interval
Table 7 Measuring points
Table 8 Limits of temperature rise of windings indirectly cooled by air
Table 9 Limits of temperature rise of windings indirectly cooled by hydrogen
Table 10 Adjustments to limits of temperature rise at the operating site of indirect cooled windings to take account of non-reference operating conditions and ratings
Table 11 Assumed maximum ambient temperature
Table 12 Adjusted limits of temperature rise at the test site (∆θT) for windings indirectly cooled by air to take account of test site operating conditions
Table 13 Limits of temperature of directly cooled windings and their coolants
Table 14 Adjustments to limits of temperature at the operating site for windings directly cooled by air or hydrogen to take account of non-reference operating conditions and ratings
Table 15 Adjusted limits of temperature at the test site θT for windings directly cooled by air to take account of test site operating conditions
9 Other performance and tests
Table 16 Minimum routine tests for machines assembled and tested in the factory of the manufacturer
Table 17 Withstand voltage tests
Table 18 Test voltage factors for machines with an assigned Impulse Voltage Insulation Class (IVIC) according to IEC 60034-18-41 and IEC 60034-18-42
Table 19 Maximum safe operating speed (min-1) of three-phase single-speed cage induction motors for voltages up to and including 1 000 V
Table 20 Overspeeds
Table 21 Cross-sectional areas of earthing conductors
Table 22 Schedule of tolerances on values of quantities
Table B.1 Electromagnetic emission limits per CISPR 11 Class B Group 1
Table B.2 Electromagnetic emission limits per CISPR 11 Class A Group 1
GB/T 755-2025 Rotating electrical machines - Rating and performance
1 Scope
This document is applicable to all rotating electrical machines, except rotating electrical machines for rail and road vehicles, which are covered by the IEC 60349 series of standards.
Machines within the scope of this document may also be subject to superseding, modifying or additional requirements in other standards, for example, IEC 60079 and IEC 60092.
Note: If particular clauses of this document are modified to meet special applications, for example machines subject to radioactivity or machines for aerospace, all other clauses apply insofar as they are compatible.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 21210-2016 Starting performance of single-speed three-phase cage induction motors (IEC 60034-12:2016, IDT)
IEC 60027-1 Letter symbols to be used in electrical technology - Part 1 : General
Note: GB/T 2987-1996 Letter symbols of parameter for electronic tubes (IEC 60027-1:1992, NEQ)
IEC 60027-4 Letter symbols to be used in electrical technology - Part 4:Rotating electric machines
IEC 60034-2 (All parts) Rotating electrical machines - Part 2:Standard methods for determining losses and efficiency from tests (excluding machines for traction vehicles)
IEC 60034-3 Rotating electrical machines - Part 3:Specific requirements for synchronous generators driven by steam turbines or combustion gas turbines
IEC 60034-5 [Rotating electrical machines - Part 5:Degrees of protection provided by the integral design of rotating electrical ma- chines(IP code) - Classification]
Note: GB/T 4942-2021 Degrees of protection provided by the integral design of rotating electrical machines (IP code) - Classification (IEC 60034-5:2020, IDT)
IEC 60034-6 Rotating electrical machines - Part 6: Methods of cooling(IC code)
Note: GB/T 1993-1993 Cooling methods for rotating electrical machines (IEC 60034-6:1991, IDT)
IEC 60034-8 Rotating electrical machines - Part 8:Terminal markings and direction of Rotation
Note: GB/T 1971-2021 Rotating electrical machines - Terminal markings and direction of rotation (IEC 60034-8:2014, IDT)
IEC 60034-12 Rotating electrical machines - Part 12:Starting performance of single-speed three-phase cage induction motors
Note: GB/T 21210-2016 Starting performance of single-speed three-phase cage induction motors (IEC 60034-12:2016, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-411 and the following apply.
Note 1: For definitions concerning cooling and coolants, other than those in 3.17 to 3.22, see IEC 60034-6.
Note 2: For the purposes of this document, the term “agreement” means “agreement between the manufacturer and purchaser’.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
- IEC Electropedia: available at http://www.electropedia.org/;
- ISO online browsing platform: available at http://www.iso.org/obp
3.1
rated value
quantity value assigned, generally by a manufacturer, for a specified operating condition of a machine
Note: The rated voltage or voltage range is the rated voltage or voltage range between lines at the terminals.
[Source: GB/T 2900.25-2008, 411-51-23]
3.2
rating
set of rated values and operating conditions
[Source: GB/T 2900.25-2008, 411-51-24]
3.3
rated output
value of the output included in the rating
3.4
load
all the values of the, in case of a generator, electrical and, in case of a motor, mechanical quantities that signify the demand made on a rotating machine by an electrical circuit or a mechanism at a given instant
[Source: GB/T 2900.25-2008, 411-51-01, modified]
3.5
no-load (operation)
state of a machine rotating with zero output power (but under otherwise normal operating conditions)
[Source: GB/T 2900.25-2008, 411-51-02, modified]
3.6
full load
load which causes a machine to operate at its rating
[Source: GB/T 2900.25-2008, 411-51-10]
3.7
full load value
quantity value for a machine operating at full load
[Source: GB/T 2900.25-2008, 411-51-11]
Note: This concept applies to power, torque, current, speed, etc.
3.8
rest and de-energized
complete absence of all movement and of all electrical supply or mechanical drive
[Source: GB/T 2900.25-2008, 411-51-03]
3.9
duty
statement of the load(s) to which the machine is subjected, including, if applicable, starting, electric braking, no-load and rest and de-energized periods, and including their durations and sequence in time
[Source: GB/T 2900.25-2008, 411-51-06]
3.10
duty type
continuous, short-time or periodic duty, comprising one or more loads remaining constant for the duration specified, or a non-periodic duty in which generally load and speed vary within the permissible operating range
[Source: GB/T 2900.25-2008, 411-51-13]
3.11
cyclic duration factor
ratio between the period of loading, including starting and electric braking, and the duration of the duty cycle, expressed as a percentage
[Source: GB/T 2900.25-2008, 411-51-09]
3.12
locked rotor torque
minimum measured torque the motor develops at its shaft and with the rotor locked, over all its angular positions, at rated voltage and frequency
[Source: GB/T 2900.25-2008, 411-48-06]
3.13
locked rotor current
greatest steady-state r.m.s. current taken from the line with the rotor locked, over all angular positions of its rotor, at rated voltage and frequency
[Source: GB/T 2900.25-2008, 411-48-16]
3.14
pull-up torque (of an a.c. motor)
minimum steady-state asynchronous torque which the motor develops between zero speed and the speed which corresponds to the breakdown torque, when the motor is supplied at the rated voltage and frequency
Note 1: This definition does not apply to those asynchronous motors of which the torque continually decreases with increase in speed.
Note 2: In addition to the steady-state asynchronous torques, harmonic synchronous torques, which are a function of rotor load angle, will be present at specific speeds.
At such speeds, the accelerating torque may be negative for some rotor load angles.
Experience and calculation show this to be an unstable operating condition and therefore harmonic synchronous torques do not prevent motor acceleration and are excluded from this definition.
3.15
breakdown torque (of an a.c. motor)
maximum steady-state asynchronous torque which the motor develops without an abrupt drop in speed, when the motor is supplied at the rated voltage and frequency
Note: This definition does not apply to asynchronous motors with torques that continually decrease with increase in speed.
3.16
pull-out torque (of a synchronous motor)
maximum torque which the synchronous motor develops at synchronous speed with rated voltage, frequency and field current
3.17
cooling
procedure by means of which heat resulting from losses occurring in a machine is given up to a primary coolant, which may be continuously replaced or may itself be cooled by a secondary coolant in a heat exchanger
[Source: GB/T 2900.25-2008, 411-44-01]
3.18
coolant
medium, liquid or gas, by means of which heat is transferred
[Source: GB/T 2900.25-2008, 411-44-02]
3.19
primary coolant
medium, liquid or gas, which, being at a lower temperature than a part of a machine and in contact with it, removes heat from that part
[Source: GB/T 2900.25-2008, 411-44-03]
3.20
secondary coolant
medium, liquid or gas, which, being at a lower temperature than the primary coolant, removes the heat given up by this primary coolant by means of a heat exchanger or through the external surface of the machine
[Source: GB/T 2900.25-2008, 411-44-04]
3.21
direct cooled (inner cooled) winding
winding mainly cooled by coolant flowing in direct contact with the cooled part through hollow conductors, tubes, ducts or channels which, regardless of their orientation, form an integral part of the winding inside the main insulation
Note: In all cases when “indirect” or “direct”’ is not stated, an indirect cooled winding is implied.
[Source: GB/T 2900.25-2008, 411-44-08]
3.22
indirect cooled winding
any winding other than a direct cooled winding
Note: In all cases when “indirect” or “direct” is not stated, an indirect cooled winding is implied.
[Source: GB/T 2900.25-2008, 411-44-09]
3.23
supplementary insulation
independent insulation applied in addition to the main insulation in order to ensure protection against electric shock in the event of failure of the main insulation
3.24
moment of inertia
sum (integral) of the products of the mass elements of a body and the squares of their distances (radii) from a given axis
3.25
thermal equilibrium
state reached when the temperature rises of the heating parts of the machine do not vary by more than a gradient of 1 K per half hour
Note: Thermal equilibrium may be determined from the time-temperature rise plot when the straight lines between points at the beginning and end of two successive intervals of half hour each have a gradient of 1K or less per half hour or 2K or less per hour.
[Source: GB/T 2900.25-2008, 411-51-08, modified]
Contents of GB/T 755-2025
Contents
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Duty
5 Rating
6 Site conditions
7 Electrical operating conditions
8 Thermal performance and tests
9 Other performance and tests
10 Information requirements
11 Miscellaneous requirements
12 Tolerances
13 Electromagnetic compatibility (EMC)
14 Application requirements
Annex A (informative) Guidance for the application of duty type S10 and for establishing the value of relative thermal life expectancy TL
Annex B (informative) Electromagnetic compatibility (EMC) limits
Bibliography
Figure 1 Continuous running duty – Duty type S1
Figure 2 Short-time duty - Duty type S2
Figure 3 Intermittent periodic duty – Duty type S3
Figure 4 Intermittent periodic duty with starting – Duty type S4
Figure 5 Intermittent periodic duty with electric braking – Duty type S5
Figure 6 Continuous operation periodic duty – Duty type S6
Figure 7 Continuous operation periodic duty with electric braking – Duty type S7
Figure 8 Continuous operation periodic duty with related load/speed changes – Duty type S8
Figure 9 Duty with non-periodic load and speed variations – Duty type S9
Figure 10 Duty with discrete constant loads – Duty type S10
Figure 11 Voltage and frequency limits for motors and for generators except generators or synchronous compensators within the scope of IEC 60034-3 and hydro generators within the scope of IEC 60034-33
Figure 12 Worst case increase in temperature rise (∆θ) and reduction of output power (∆P) of motors as a function of the combined change of voltage and frequency |△φ | indicative guideline to users of motors and generators only
Figure 13 Factor K for determining RPE,M
Table 1 Preferred voltage ratings
Table 2 Unbalanced operating conditions for synchronous machines
Table 3 CCC symbol designation
Table 4 Primary functions of machines
Table 5 Reference coolant (see also Table 11)
Table 6 Time interval
Table 7 Measuring points
Table 8 Limits of temperature rise of windings indirectly cooled by air
Table 9 Limits of temperature rise of windings indirectly cooled by hydrogen
Table 10 Adjustments to limits of temperature rise at the operating site of indirect cooled windings to take account of non-reference operating conditions and ratings
Table 11 Assumed maximum ambient temperature
Table 12 Adjusted limits of temperature rise at the test site (∆θT) for windings indirectly cooled by air to take account of test site operating conditions
Table 13 Limits of temperature of directly cooled windings and their coolants
Table 14 Adjustments to limits of temperature at the operating site for windings directly cooled by air or hydrogen to take account of non-reference operating conditions and ratings
Table 15 Adjusted limits of temperature at the test site θT for windings directly cooled by air to take account of test site operating conditions
9 Other performance and tests
Table 16 Minimum routine tests for machines assembled and tested in the factory of the manufacturer
Table 17 Withstand voltage tests
Table 18 Test voltage factors for machines with an assigned Impulse Voltage Insulation Class (IVIC) according to IEC 60034-18-41 and IEC 60034-18-42
Table 19 Maximum safe operating speed (min-1) of three-phase single-speed cage induction motors for voltages up to and including 1 000 V
Table 20 Overspeeds
Table 21 Cross-sectional areas of earthing conductors
Table 22 Schedule of tolerances on values of quantities
Table B.1 Electromagnetic emission limits per CISPR 11 Class B Group 1
Table B.2 Electromagnetic emission limits per CISPR 11 Class A Group 1
