Induction motor International and Indian Standards used in Designing

Induction motors are backbone of any industry. There are various International and Indian Standards while designing and selection of motors. While selection of induction motors following standards are used:-

Codes and Standards used in Designing and Selection for Induction motors

Codes and Standards	Description
IEC 60034-1, IEC 60085, DIN EN 60034-1	General specifications for rotating electrical machines
IEC 60034-2, DIN EN 60034-2	Specification of the losses and efficiency of rotating electrical machines
IEC/EN 61241, DIN EN 61241	Areas containing flammable dust
IEC/EN 60079-15, DIN EN 60079-15	Type of protection “n” (non-sparking)
IEC/EN 60079-7, DIN EN 60079-7	Increased safety “e”
IEC/EN 60079-1, DIN EN 60079-1	Explosion-proof enclosure “d”
IEC/EN 60079-0, DIN EN 60079-0	General regulations
IEC 60034-5, DIN EN 60034-5	Degrees of protection of rotating electrical machines
DIN ISO 10816	Vibration limits
IEC 60034-14, DIN EN 60034-14	Vibration severity of rotating electrical machines
IEC 60034-6, DIN EN 60034-6	Cooling methods for rotating electrical machines
IEC 60038 ,DIN IEC 60038	IEC standard voltages
IEC 60034-9, DIN EN 60034-9	Noise limit values for rotating electrical machines
IEC 60034-11 ,DIN EN 60034-11	Built-in thermal protection
IEC 60072 fixing only, DIN EN 50347	Asynchronous AC motors for general use with standardized dimensions and outputs
IEC 60034-12, DIN EN 60034-12	Restart characteristics for rotating electrical machines
IEC 60034-, DIN EN 60034-8	Terminal designations and direction of rotation for electrical machines
IEC 60034-7 , DIN EN 60034-7	Designation for type of construction, installation and terminal box position
DIN 42925	Entry to terminal box
IS 325	Three phase induction motors
IS 1231	Dimensions of three phase foot mounted induction motors
IS 1271	Thermal evaluation and classification of electrical insulation
IS 2148	Flameproof enclosures for electrical apparatus
IS 2223	Dimensions of Flange mounted A.C. induction motors
IS 2253	Designation for Types of construction and mounting arrangements of rotating electrical machines
IS 2254	Dimensions of vertical shaft motors for pumps
IS 2968	Slide rails for electric motors, dimensions
IS 4029	Guide for testing 3 phase Induction Motors
IS 4691	Degree of protection provided by enclosures for rotating electrical machinery
IS 4722	Rotating electrical machines
IS 4728	Terminal marking and direction of rotation for rotating electrical machinery
IS 4889	Method of determination of efficiency of rotating electrical Machines
IS 5571	Guide for selection of electrical equipment for hazardous areas
IS 6362	Methods of cooling for rotating electrical machines
IS 8223	Dimensions and output ratings for foot mounted rotating electrical machines with frame numbers 355 to 1080.
IS 9628	Specification for three phase induction motors with type of protection ‘n’
IS 8789	Values of performance characteristics for 3 phase Induction motors
IS 6381	Construction & testing of electrical apparatus with type of protection 'e'
IS 7389	Pressurized enclosure of electrical equipment for use in hazardous area.
IS 7816	Guide for testing insulation resistance of rotating machines.
IS 8289	Specifications for electrical equipment with type of protection ‘n’.
IS 12065	Permissible limits of noise level for rotating electrical machines
IS 12075	Mechanical vibration of rotating electrical machines with shaft heights 56mm and higher-Measurement, evaluation and limits of vibration severity
IS 12802	Temperature rise measurement of rotating electrical machines.
IS 13529	Guide on effects of unbalanced voltages on the performance of three phase cage induction motors.
IS 13555	Guide for selection and application of three phase induction motors for different types of driven equipment.

These are different standards used while procurement of Induction motors.

400 KVA Transformer Technical Specifications

Transformers are backbone of electrical systems. Transformers are used for both stepping up and stepping down the voltage. While procurement of  Distribution Transformers there are following technical aspects which should be considered :-

For Tan-delta, Loss angle test visit link:-

http://electrialstandards.blogspot.com/2015/10/tan-delta-test-loss-angle-test.html

Below are the technical specifications of Oil type 400 KVA transformer :-

1.       Transformer voltage ratio should be 11 KV/ 433 V

2.       Vector group should be Dyn11

3.       Transformer Impedance at 75 degree Celsius should be 5%

4.       Transformer-400 KVA maximum no load losses should 0.7 KW

5.       Transformer-400 KVA Maximum full load losses should be 5.1 KW

6.       Transformer Oil Temperature rise without enclosure  should be 35 Deg C max over ambient 40 Deg C

7.       Transformer Winding Temperature rise without enclosure should be 40 Deg C max over ambient 40 Deg C

8.       Current density of LT and HT winding should be 3 A/mmsq for 400 KVA Transformer.

9.       Tapping on HT winding should be off load with +/- 5% in 2.5% step

10.    Design clearances for Phase to phase for 11 KV system should be 180 mm and Phase to earth for 11KV system should be 120 mm for 400 KVA Transformer.

11.   Design clearances for Phase to phase for 433 KV system should be 25 mm and Phase to earth for 433KV system should be 25 mm for 400 KVA Transformer.

12.    Transformer Type should be  Double Copper wound, three phase, oil immersed, with ONAN cooling

13.   Voltage variation on Supply side should be +/- 10%

14.   Frequency variation on Supply Side should be +/- 5%

15.   Insulation level for one minute power frequency withstand voltage should be 3KV for 433V system & 28KV for 11KV system for 400 KVA transformer.

16.   Insulation level for Lightning impulse withstand voltage should be 75KV peak for 11KV system for 400 KVA transformer.

17.   Short circuit withstand level should be 3 Sec with 5% impedance

18.   Noise level for Transformer should not exceed limits as per NEMA TR-1 with all accessories running measured as per IEC 551 / NEMA standard running measured as per IEC 551 / NEMA standard

For Transformer Oil Filteration process visit link:-

http://electrialstandards.blogspot.in/2015/10/transformer-oil-filtration-process.html

19.   Transformer tank design should be as below:-

	Tank	Type Tested Design
	Design	a) Completely sealed type with corrugated fins and with/without conservator tank as per site requirements  b) Completely oil filled or N2 cushion at top filled with positive pressure. N2 shall be technical grade in accordance with IS:1747  c) With bolted / welded cover
	Plate / Corrugated fin / tank features	a) Adequate for meeting mechanical & electrical withstand requirements, as per applicable standard. b) The tank and its sealing (gaskets, o-rings, etc.) shall be of adequate strength to withstand positive and negative pressures built-up inside the tank while the transformer is in operation. The maximum pressure generated inside the tank should not exceed 40kPa, positive or negative. c) Corrugated fins shall be built up of CRCA sheets of minimum 1.2mm thick. d) The corrugated tank wall shall ensure sufficient cooling of the transformer and compensate for the changes in the oil volume during operation.  e) The transformer shall be capable of giving continuous rated output, without exceeding the specified temperature rise. f) Internal clearance of tank shall be such that, it shall facilitate easy lifting of core with coils from the tank and HV & LV bushings mounted on Top cover.  g) All joints of tank and fittings shall be oil tight. The tank design shall be such that the core and windings can be lifted freely with cover. The tank plate shall be of such strength that the complete transformers when filled with oil may be lifted bodily by means of lifting lugs. h) Tanks with corrugations & without conservator shall be tested for leakage at a pressure as per the applicable standard.
	Material of Construction	Mild steel plate with low carbon
	Plate Thickness	To meet the requirements of pressure and vacuum type tests as per CBIP manual
	Welding features	a) All seams and joints shall be double welded b) All welding shall be stress relieved for sheet thickness greater than 35 mm c) All pipes, stiffeners, welded to the tank shall be welded externally  d) All corrugated fins or expansion bellows provided shall be double welded.
	Tank features	a) Bottom with stiffeners & adequate space for collection of sediments b) No external pocket in which water can lodge c) Tank bottom with welded skid base d) Strength to prevent permanent deformation during lifting, jacking, transportation with oil filled. e) Minimum disconnection of pipe work and accessories for cover lifting  f) Tank to be designed for oil filling under vacuum g) Tank cover fitted with lifting lug

20.   Transformer oil should be Class 1 new mineral insulating oil, shall be certified not to contain PCBs. Naphthalene base with antioxidant inhibitor.

21.   Transformer winding should have following:-

	Winding
	Material	Electrolytic Copper
	Maximum Current Density allowed	Maximum 3 amp / sqmm
	Winding Insulating material	Class A, non catalytic, inert to transformer oil, free from compounds liable to ooze out, shrink or collapse.
	Winding Insulation	Uniform
	Design features	a) Stacks of winding to receive adequate shrinkage treatment. b) Connections braced to withstand shock during transport, switching, short circuit, or other transients.  c) Minimum out of balance force in the winding at all voltage ratios. d) Conductor width on edge exceeding six times its thickness. e) Transposed at sufficient intervals.  f) Coil assembly shall be suitably supported between adjacent sections by insulating spacers + barriers. g) Winding leads rigidly supported, using guide tubes if practicable.  h) Winding structure & insulation not to obstruct free flow of oil through ducts. i) Delta connection shall be done using Flexible cable.

22.   Transformer Bushings and Terminations should have following technical specifications:-

	Bushings and Terminations
	Type of HV side bushing	Epoxy cast bushing, 630 Amp, interface type ‘C’ as per EN50180 and EN50181.
	Type of LV side bushing	Indoor, Epoxy resin cast, 1kv voltage class and creepage 31mm/KV
	Essential provision for LV side line bushing	It shall be complete with copper palm suitable for tinned copper busbar of size 100x12 mm
	Essential provision for LV side neutral bushing	In case of neutral bushing the stem and bus bar palm shall be integral without bolted, threaded, brazed joints. Bus bar size shall be 100x12 mm
	Arcing Horn	As per site requirements
	Termination on HV side bushing	Cable connection by screened separable connector kit.
	Termination of LV side bushing	Bus bar connections
	Minimum creepage distance of all bushings and support insulators.	31mm/kv
	Protected creepage distance	At least 50 % of total creepage distance
	Continuous Current rating	Minimum 20 % higher than the current corresponding to the minimum tap of the transformer
	Rated thermal short time current	26.3kA for 3 sec
	Bushing terminal lugs in oil and air	Tinned copper

23.   Current Transformers used for Transformers should have following Technical specifications:-

Current Transformers	All three phases and neutral on LV side
Maintenance requirements	Replacement should be possible by removing fixing nut of mounting plate without disturbing LT bushing
Accuracy Class	5P10
Burden	5VA
Type	Resin Cast Ring type suitable for outdoor use
CT ratio	400KVA -1000/5 Amp

24.    Transformer Name plate should consists of following Parameters:-

For Parallel Operation of Transformers Visit link:-

http://electrialstandards.blogspot.com/2015/10/parallel-operation-of-transformers.html

Following details shall be provided on rating and diagram plate as a minimum.

a)      Type/kind of transformer with winding material.

b)      IS/ IEC [R3] standard to which it is manufactured.

c)       Manufacturer's name.

d)       Transformer serial number.

e)       Month and year of manufacture.

f)        Rated frequency in HZ.

g)       Rated voltages in KV.

h)      Number of phases.

i)        Rated power in KVA.

j)        Type of cooling (ONAN).

k)      Rated currents in Amp.

l)        Vector group connection symbol.

m)    1.2/50µs wave impulse voltage withstands level in KV.

n)      Power frequency withstands voltage in KV.

o)      Impedance voltage at rated current and frequency in percentage at principal, minimum and maximum tap

p)      Load loss at rated current.

q)      No-load loss at rated voltage and frequency

r)        Continuous ambient temperature at which ratings apply in deg c

s)       Top oil and winding temperature rise at rated load in deg c;

t)        Winding connection diagram with taps and table of tapping voltage, current and power

u)      Transport weight of transformer

v)      Weight of core and windings

w)    Total weight

x)      Volume of oil

y)       Weight of oil

z)      Name of the purchaser

25.    Transformer to be designed for suppression of 3rd, 5th, 7th harmonic voltages and high frequency disturbances

26.    Transformer core should have following technical specifications:-

Core
Grade	High grade , non- ageing, low loss, high permeability, grain oriented, cold rolled silicon steel lamination
Core Design Features	a) Magnetic circuit designed to avoid short circuit paths within core or to the earthed clamping structures. b) Magnetic circuit shall not produce flux components at right angles to the plane of lamination to avoid local heating.  c) Least possible air gap and rigid clamping for minimum core loss and noise generation. d) Adequately braced to withstand bolted faults on secondary terminals without mechanical damage and damage/ displacement during transportation and positioning.  e) Percentage harmonic potential with the maximum flux density under any condition limited to avoid capacitor overloading in the system.  f) All steel sections used for supporting the core shall be thoroughly sand blasted after cutting, drilling, welding. g) Provision of lifting lugs for core coil assembly. h) Supporting framework designed not to obstruct complete drainage of oil from transformer

For Parallel operation of Transformers visit link:-

http://electrialstandards.blogspot.com/2015/10/parallel-operation-of-transformers.html

For Tan-delta, Loss angle test visit link:-

http://electrialstandards.blogspot.com/2015/10/tan-delta-test-loss-angle-test.html