Standards International standardisation work in the field of electrical engineering is well developed. There are two organisations: IEC (International Electrotecnical Commission) and CENELEC (Comité Européen de Normalisation Electrotechnique). IEC works on global scale while CENELEC concentrates on regional work in Western Europe. The International Standardisation Organisation ISO also has particular interest in electric motors. The IEC has some 45 member countries; CENELEC has 17. The aim of CENELEC is to remove obstacles to technical trade in Western Europe due to differences in regulations and standards. Existing IEC publications are generally used as a basis, but additions can be made. New national standards are increasingly identical to or largely based on Europeans standards issued by CENELEC. The offered motor shall at the time of delivery comply with all the relevant standards and specifications, in particular the following: Title
Standard
General requirements for rotating electrical machines
IEC 34-1 IEC 85
Fixing dimensions and assignment of rated output with IM B 3
IEC 72
Terminal markings and direction of rotation of IEC 34-8 rotating electrical machines Types of construction of rotating electrical machines
IEC 34-7
Method of cooling rotating electrical machinery
IEC 34-6
Degrees of protection by enclosures for rotating electrical machinery
IEC 34-5
Vibration severity of electrical machines
IEC 34-14, ISO 2373
Parallel shaft extensions for electrical machines
IEC 72
Noise emission limits
IEC 34-9
Starting performance
IEC 34-12
IEC standard voltages
IEC 38
Methods for determining losses and efficiency IEC 34-2 of rotating electrical machinery from test
1 Tolerances 1.1 Electrical data The following tolerances according to IEC 34-1 are permitted: Table I. Electrical tolerances Performance characteristic indirect calculation
Efficiency direct method Power factor
Permissible tolerance
Notes
- 15% of (1-η (1- η) P N ≤ 50 kW - 10% of (1-η (1- η) P N > 50 kW - 15% of (1-η (1- η)
.
min 0.02 max 0.07
Slip
at rated load operating temperature
±
Starting current
in the planned starting circuit
+ 20% + 10% for frame size 56 - 160
20% ατ Π N ≥ 1 kW
Starting torque
- 15% and + 25%
Pull-up torque
- 15 %
Pull-out torque
- 10%
Moment of inertia
±
Noise level
+ 3 dB(A)
without restriction downwards
with the applications of the tolerance T K /T N at least 1.6
10% sound pressure level
These tolerances are permissible for the values assured for three-phase asynchronous motors, taking the necessary manufacturing tolerances and material variations of the raw materials used, into account. 1.2 Mechanical parameters Table II. Mechanical fit or tolerances Mechanical dimension
Fit or tolerance
Largest width of motor (without terminal box)
+ 2%
Overall length of motor
+ 1%
Overall height (lower edge foot, housing or flange to highest point of motor)
+ 2%
2 Frame sizes In the IEC-publication 72-1 (1991) frame sizes and the most essential fixing dimensions are fixed and co-ordinated to the individual frame size.
Table III. Frame size
Thread A/mm
B/mm
C/mm
D/mm
E/mm
F/mm
G/mm
H/mm
71-14
112
90
45
14
30
5
11
71
M6
80-19
125
100
50
19
40
6
15.5
80
M8
90S24
140
100
56
24
50
8
20
90
M8
90L24
140
125
56
24
50
8
20
90
M8
100L28
160
140
63
28
60
8
24
100
M10
112M28
190
140
70
28
60
8
24
112
M10
132S38
216
140
89
38
80
10
33
132
M10
132M38
216
178
89
38
80
10
33
132
M10
160M42
254
210
108
42
110
12
37
160
M12
160L42
254
254
108
42
110
12
37
160
M12
180M48
279
241
121
48
110
14
42.5
180
M12
180L48
279
279
121
48
110
14
42.5
180
M12
200M55
318
267
133
55
110
16
49
200
M16
200L55
318
305
133
55
110
16
49
200
M16
3 Types of duty Various types of duty have been defined in terms of how the load, and thus the output of the motor, varies with time. The rated output for each type of duty is determined in a load test which the motor must undergo without the temperature limits laid down in IEC Publication 34-1 (1994) being exceeded. Duty types are: Table IV. Duty types Duty type
Designation
Duty type
Designation
S1
Continuos duty
S6
Continuos-operating periodic duty
S2
Short-time duty
S7
Continuos-operation periodic duty with electrical braking
S3
Intermittent periodic duty without starting
S8
Continuos-operation periodic duty with related load/speed changes
S4
Intermittent periodic duty with starting
S9
Duty with non-periodic and speed variations
S5
Intermittent periodic duty with electrical braking
4 Insulation According to IEC 85, insulation is divided into insulation classes. Each class has a designation corresponding to the temperature that is upper limit of the range of appli cations of the insulation material under normal operating conditions and with satisfactory life. If this upper limit is exceeded, the life of the insulation will be shorten. The correct insulation for the winding of a motor is therefore determined by both the temperature rise in the motor and the temperature of the ambient air. If a motor is subjected to an ambient temperature higher than 40 oC, it must normally derated or an insulating material of an higher class must be used. Temperature limits of the different insulation classes is shown Fig. 1.
Fig. 1. Temperature limits according to I EC 85
5 Protection
Degree of protection are defined in IEC Publication 34-5 and are stated as the letters IP (International Protection) followed by two digits. The first digit states the degree of protection against contact and the penetration of solid objects (Table V). The second digit states the degree of protection against water (Table VI). Table V. The first digit mean First digit
Protection against contact and the entry of objects
0
No special protection of persons against accidental or inadvertent contact with live or moving parts. No protection of machine against ingress of solid foreign bodies
1
Protection against accidental or inadvertent contact with live and moving parts inside the enclosure by a large surface of human body. Protection against ingress of large solid foreign bodies (diameter greater than 50 mm).
2
Protection against contact by finger with live or moving parts inside the enclosure. Protection against ingress of small solid foreign bodies (diameter greater than 12 mm).
4
Protection against contact with live or moving parts inside the enclosure by tools, wires, or such objects of thickness greater than 1 mm. Protection against ingress of small solid foreign bodies (diameter > 1 mm) excluding the ventilation openings (intake and discharge of external fans) and the drain hole of enclosed machine which may have degree 2 protection.
5
Complete protection against contact with live or moving parts inside the enclosure. Protection against harmful deposits of dust. The ingress of dust is not totally prevented, but dust cannot enter in an amount sufficient to interfere with satisfactory operation of the machine.
Table VI. The second digit mean Second digit
Protection of harmful ingress of water
0
No special protection.
1
Dripping water (vertically falling drops) shall have no harmful effect.
2
Drop of water falling at any angle up to 15 o from the vertical shall have no harmful effect.
3
Water falling as a spray at an angle equal to or smaller than 60 o with respect to the vertical shall have no harmful effect.
4
Water splashed against the machine from any direction shall have no harmful effect.
5
Water protection by a nozzle against the machine from any direction shall have no harmful effect.
6
Water from heavy seas shall not enter the machine in harmful quantity.
7
Ingress of water into the machine in a harmful quantity shall not be possible when the machine is immersed in water under stated conditions of pressure and time.
8
Ingress of water into machine in a harmful quantity shall not be possible when the machine is immersed in water under a specified pressure and for an indefinite time.
A letter S added after the digits means that the machine has been tested when stationary. The letter W between IP and the digits indicates a weatherproof version; this means that the version is protected against harmful ingress of rain, snow and solid air-bone particles. 6 Cooling IEC Publication 34-6 lays down cooling methods for air cooled motors. There are two types of code, a simple code for commonest types of motor and a more detailed code for more complex cooling systems. the cooling method is specified with the letter IC (International Cooling) followed by a group of digits. The first digit indicates the arrangement of cooling circuit. The second digit indicates the method of supplying power to circulate the cooling medium. Table VII. Cooling type Code
Brief description
IC 01
Free circulation, self-circulation
IC 06
Free circulation, independent component mounted on the machine
IC 11
Inlet pipe ventilated, self-circulation
IC 17
Inlet pipe ventilated, independent and separate device for coolant system pressure
IC 21
Outlet pipe ventilated, self-circulation
IC 27
Outlet pipe ventilated, independent and separate device for coolant system pressure
IC 31
Inlet and outlet pipe ventilated, self-circulation
IC 37
Inlet and outlet ventilated, independent and separate device for coolant system pressure
IC 41
Frame surface cooled, self-circulation
IC 51
Integral heat exchanger using surrounding medium, self-circulation
The more detailed code describes cooling circuits. The first code group of one letter and two digits indicates the low-temperature outer secondary cooling circuit. The second code group of one letter and two digits indicates the higher-temperature inner primary cooling circuit. The letter A stands for air and letter W for water. Where only air is used, the letter A may be omitted. 7 Type of construction Classification of types of constructions and mounting arrangements (IM Code) are published in IEC 34-7. It lays down two ways of starting how a motor is mounted. Code I covers only motor with bearing end shields and one shaft extension. Code II is a general code. Fig. 2 includes the designations for the most commonly occurring mounting arrangements according to the two codes.
Fig. 2. Common mounting arrangements.
8 Starting performance IEC Publication 34-12 applies to the starting performance of single speed three phase cage induction motors for voltage up to and including 660 V, intended for normal torque design (N) at frequencies of 50 or 60 Hz, high torque deign (H) at a frequency of 60 Hz and NY and HY for star-delta starting. Motors rated on the basis of duty-type S1 (maximum continuous rating) and they may have any degree of protection. All data is given in relation to rated power and for 2, 4, 6 and 8 poles. The standard also states the maximum permissible moment of inertia with regard to the temperature rise of the motor during starting.
8.1 Design N starting torque The starting torque is represented by the locked rotor torque T l, pull-up torque T u and breakdown torque T b each expressed as a per unit values of rated torque T N and shall
be in accordance with the appropriate values given in Table VIII. These values are minimum values at rated voltage, with no tolerance. Higher values are allowed. Locked rotor torque is the minimum measured torque, which the motor develops with the rotor locked at rated voltage applied at rated frequency. TableVI II. Torques for design N starting performance Number of poles Power range
2
4
6
8
(kW)
T l
T u
b T
T l
T u
b T
T l
T u
b T
T l
T u
b T
0.4 < Pn 0.63
1.9
1.3
2.0
2.0
1.4
2.0
1.7
1.2
1.7
1.5
1.1
1.6
0.63 < Pn 1.0
1.8
1.2
2.0
1.9
1.3
2.0
1.7
1.2
1.8
1.5
1.1
1.7
1.0 < Pn 1.6
1.8
1.2
2.0
1.9
1.3
2.0
1.6
1.1
1.9
1.4
1.0
1.8
1.6 < Pn 2.5
1.7
1.1
2.0
1.8
1.2
2.0
1.6
1.1
1.9
1.4
1.0
1.8
2.5 < Pn 4.0
1.6
1.1
2.0
1.7
1.2
2.0
1.5
1.1
1.9
1.3
1.0
1.8
4.0 < Pn 6.3
1.5
1.0
2.0
1.6
1.1
2.0
1.5
1.1
1.9
1.3
1.0
1.8
6.3 < Pn 10
1.5
1.0
2.0
1.6
1.1
2.0
1.5
1.1
18.
1.3
1.0
1.7
10 < Pn 16
1.4
1.0
2.0
1.5
1.1
2.0
1.4
1.0
1.8
1.2
0.9
1.7
16 < Pn 25
1.3
0.9
1.9
1.4
1.0
1.9
1.4
1.0
1.8
1.2
0.9
1.7
25 < Pn 40
1.2
0.9
1.9
1.3
1.0
1.9
1.3
1.0
1.8
1.2
0.9
1.7
40 < Pn 63
1.1
0.8
1.8
1.2
0.9
1.8
1.2
0.9
1.7
1.1
0.8
1.7
63 < Pn 100
1.0
0.7
1.8
1.1
0.8
1.8
1.1
0.8
1.7
1.0
0.7
1.6
100 < Pn 160
0.9
0.7
1.7
1.0
0.8
1.7
1.0
0.8
1.7
0.9
0.7
1.6
160 < Pn 250
0.8
0.6
1.7
0.9
0.7
1.7
0.9
0.7
1.6
0.9
0.7
1.6
250 < Pn 400
0.75
0.6
1.6
0.75
0.6
1.6
0.75
0.6
1.6
0.75
0.6
1.6
400 < Pn 630
0.65
0.5
1.6
0.65
0.5
1.6
0.65
0.5
1.6
0.65
0.5
1.6
The minimum torque for single-speed motors (< 100 kW) delivered during run up at rated voltage must not be less than 50% of the rated torque and not less than 50% of the starting torque. For rated output ≥ 100 kW the corresponding figure is 30 and 50% respectively. The maximum torque is a measure of the overload capacity of the motor. IEC Publication 341 lays down that the general-purpose motors must be capable of developing at least 160 % of the rated torque for 15 seconds without stopping or sudden speed change if rated voltage and frequency are maintained.
8.2 Design N locked rotor apparent power The locked rotor apparent power S 1 is the apparent power input expressed as a per unit value of the rated output P N. This value shall not be greater than the appropriate values given in Table IX. The values given in Table IX are independent of the number of poles and are maximum values at rated voltage, with no tolerance. The locked rotor current is the measured steady-state rms. current taken from the line with the rotor locked with rated voltage and frequency applied. This is the value measured when, after a few cycles, the transient phenomena have died out. The transient current, the peak value, may be about 2.5 times the steady-state starting current, but decays rapidly. In the USA National Electrical Code (NEC) Article 430-52 limit the "transient" motor current when selecting overcurrent devices Table IX. Locked rotor apparent power Power range [kW]
S st/ P
0.4 < P 6.3
13
6.3 < P 25
12
25 < P 100
11
100 < P 630
10
8.3 Design N starting requirements Motors of design N shall satisfy the following starting requirements: a) They shall allow two starts in succession (coasting to rest between starts) from cold conditions or one star from hot after running at rated conditions. The retarding torque due to driven load is in each case proportional to the square of the speed and equal to the rated torque at rated speed with the external inertia I given in Table X. b) In each case a further star is permissible only if the motor temperature before starting does not exceed the steady temperature at rated load.
The values given in Table X are in terms of mr 2 (m = mass; r = mean radius of gyration) Table X. External inertia I Number of poles Power (kW)
2
2
kgm
4
2
kgm
6
2
kgm
8
2
kgm
0.4
0.018
0.099
0.273
0.561
0.63
0.026
0.149
0.411
0.845
1.0
0.040
0.226
0.624
1.28
1.6
0.061
0.345
0.952
1.95
2.5
0.091
0.516
1.42
2.92
4.0
0.139
0.788
2.17
4.46
6.3
0.210
1.19
3.27
6.71
10
0.318
1.80
4.95
10.2
16
0.485
2.74
7.56
15.5
25
0.725
4.10
11.3
23.2
40
1.1
6.26
17.2
35.4
63
1.67
9.42
26.0
53.3
100
2.52
14.3
39.3
80.8
160
3.85
21.8
60.1
123
250
5.76
32.6
89.7
184
400
8.79
49.7
137
281
630
13.2
74.8
206
423
For intermediate output values, external inertia shall be calculated according to the following formula, from which the values in the Table X have been calculated: I = 0.04 P 0.9 p2.5 kgm2, where P is the power in kW and p is the number of pairs of poles. 8.4 Design NY starting requirements
The starting requirements are as for design N. In addition, however, a reduced retarding torque is necessary as the starting torque in "star" may be insufficient to accelerate some loads to an acceptable speed. 9 Sound level IEC publication 34-9 recommends maximum limits for both sound pressure level and sound power level. There are figures for both open-type motors (IP 22) and totally- enclosed motors (IP 44). The procedure for measuring the sound level is laid down in ISO 1680. The measurements are done under free-field conditions over a reflecting floor, i.e. without reflections from walls and ceiling. The Table XI gives examples of sound pressure level for totally-enclosed motors.
Table XI. Permitted sound pressure level in dB(A) 1 meter from the surface, for totally-enclosed motors at no load as per IEC 34-9. Rated output kW
> 600
> 960
≤ 1.1
67
70
71
74
75
79
> 1.1 ≤ 2.2
69
70
73
78
80
82
> 2.2 ≤ 5.5
72
74
77
82
83
85
> 5.5 ≤ 11
75
78
81
86
87
90
> 11 ≤ 22
78
82
85
87
91
93
> 22 ≤ 37
80
84
86
89
92
95
> 37 ≤ 55
81
86
88
92
94
97
> 55 ≤ 110
84
89
92
93
96
98
> 110 ≤ 220
87
91
94
96
98
100
> 220 ≤ 400
88
92
96
98
99
102
960
> 1320
1320
> 1900
1900
> 2360
2360
> 3150
3150
3750
10 Efficiency IEC Publication 34-2 describes two methods for determining the efficiency of a motor, the direct method and the indirect method. In the direct method input power and output power are each measured individually. The indirect method involves determining the input power and the losses. The losses calculated are bearing and air friction losses, current heat losses in stator and rotor, iron losses and stray losses. The standards define the stray losses as 0.5 % of the input power at rated duty. NEMA, the standards most widely used in the USA calculates stray losses at 0.9% - 1.2 % depending on the output power. 11 Vibration The International Standardisation Organisation ISO, has issued international standards covering balancing and vibration characteristics. ISO 2373 is of particular interest for electric motors. It covers permitted vibration level on delivery and applies to motor with shaft heights in the range of 80 to 400 mm. The vibration level is expressed in mm/s rms. (millimetres per second root mean squared) and must be measured at no load with the motor on elastic mountings. ISO 2373 requires the shaft extension to be fitted with a full-size from during vibration measurement. The requirements apply in the measurement range 10 to 1000 Hz. Table XII. Vibration severity Grade of quality
Speed r/min
Maximum vibration velocity in mm/s rms. at shaft height, mm
80 - 132 160 - 225 250 - 400
N
600 ≤ 3 600
1.8
600 ≤ 1 800 > 1800 ≤ 3 600
1.71
Reduced
600 ≤ 1 800 > 1800 ≤ 3 600
0.45
Special
Normal R S
2.8
4.5
1.12
1.8
1.12
1.8
2.8
0.71 1.71
1.12 1.12
1.8
IEC 34-14 has its own recommendation for vibration characteristics; these differ slightly from ISO. Among national standards the German DIN 45665 is almost identical to ISO 2373. The parallel German recommendation VDE 2056 is differently written and uses other quality description. British standard BS 4999 Part 50 also lays down figures that correspond to ISO. The standards used in the USA are formulated in terms of displacement amplitude, not vibration velocity, but the level aimed for is more or less the same. The smooth shaft method of measurement is standard there. 12 Permitted output at high ambient temperature or high altitude above sea level Motors in their standard versions are intended to operate in an ambient temperature of 40 oC maximum and at not more than 1000 metres above sea level. If the motors are to be used at high ambient temperature or higher altitudes the rated output must normally be reduced by the percentage shown in the Table XIII. Thus when a standard motor is derated, relative data in the catalogues, such as I st/I, will change. Table XIII. Permitted output at high ambient temperature or high altitude above sea level o
Ambient temperature C
40
45
50
55
60
70
Permitted output, % at rated output
100
96.5
93
90
86.5
79
Altitude above sea level
1000
1500
2000
2500
3500
4000
Permitted output, % of rated output
100
97
94.5
92
86.5
83.5
13 Overspeed Motor shall be designed to withstand 1.2 times the maximum rated speed. 14 Voltage and frequency According to VDE 0530 a voltage variation of ± 5% is permissible for the motor. 15 Overload capacity In compliance with VDE 0530, all motors can be exposed to the following overload conditions: - 1.5 times the rated current for 2 minutes, - 1.6 times the rated torque for 15 seconds.
