The document discusses dry type transformers, which are air-cooled rather than liquid-cooled. It describes how dry type transformers do not require maintenance-intensive liquid cooling systems or fireproof vaults. The main types of dry type transformers are cast resin dry type transformers and vacuum pressure impregnated transformers. Dry type transformers provide reliable power in a safe and environmentally-friendly way, making them well-suited for applications such as buildings, tunnels, and industrial facilities where fire safety is important.

1. Name :- Smit Shah -140410109096
T.Y Electrical 2 Sem 6
Subject:-Design of DC Machine &
Transformer
Topic :-Dry Type Transformer 1

2. Introduction
• Dry type transformers require minimum
maintenance to provide many years of reliable
trouble free service. A dry-type transformer has no
moving parts and is a completely static solid state
device, under normal operating conditions, are
usually insure a long and trouble-free life. Unlike
liquid fill transformers which are cooled with oil or
fire resistant liquid dielectric, dry type units utilize
only environmentally safe, CSA and UL recognized
high temperature insulation systems.
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3. • Dry type transformers provide a safe and reliable
power source which does not require fire proof
vaults, catch basins or the venting of toxic gasses.
These important safety factors allow the installation
of dry type transformers inside buildings close to the
load, which improves overall system regulation and
reduces costly secondary line losses.
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4. • Fire-resistant dry type or "cast resin" transformers
are well suited for installation in high-rise buildings,
hospitals, underground tunnels, school, steel
factories, chemical plants and places where fire
safety is a great concern. Hazard free to the
environment, dry type transformers have over the
years proven to be highly reliable. “Dry type” simply
means it is cooled by normal air ventilation.
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5. • The dry type transformer does not require a liquid
such as oil or silicone or any other liquid to cool the
electrical core and coils. Dry type transformers are
voltage changing (Step-up or Step-down) or isolation
device that is air cooled rather than liquid cooled.
The transformer case is ventilated to allow air to flow
and cool the coil (coils).
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6. • Dry type transformers differ from liquid-filled units in
many ways, and separate industry standards apply to
their design, construction, and maintenance. Dry-
Type Transformers suitable for indoor and outdoor
applications anywhere that safe and dependable
power are important. Cooling ducts in the windings
allow heat to be dissipated into the air.
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7. What is Dry Type Transformer?
• Dry type transformer never uses any insulating liquid
where its winding with core be immerged. Rather
windings with core are kept within a sealed tank that
is pressurized with air.
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8. Type of Dry Type Transformer
• Cast Resin Dry Type Transformer ( CRT)
• Vacuum pressure Impregnated Transformer
( VPI)
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9. Cast Resin Dry Type Transformer
(CRT)
• Cast resin dry type transformer (CRT) is used in the
high moisture prone areas. It is because of its
primary and secondary windings are encapsulated
with epoxy resin. This encapsulation helps to prevent
moisture to penetrate to affect the winding material.
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10. • Complete protection is achieved by this cast resin
encapsulation so that the transformer can work
without disruption in highly moisture prone area.
Thus this transformer is non hygroscopic. This type of
transformer is available in ratings of 25 KVA to
12,500 KVA. with insulation class of F (90°C Temp.
Rise).
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11. Vacuum Pressure Impregnated
Transformer (VPI)
• This type of transformer is made with minimum
flammable material as insulation of windings. The
windings of this transformer are made in foil or strip
in a continuous layer. But for higher voltages, the
winding is made of disks that are connected in series
or parallel as per power rating with respect to
voltage level.
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12. • The insulation of the winding is void free
impregnation that is made with class H polyester
resin. The primary and secondary winding with core
are laced safely within a vacuum protective box.
Moisture Ingress Protection is high and it never gets
affected by moisture. This type of transformer is
available from 5 KVA to 30MVA with insulation grade
F(155oC) and H(180oC). It’s with Protection up to IP56
.
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13. Advantages of Dry Type Transformer
• Safety for people and property.
• Maintenance and pollution-free solution.
• Easy installation.
• Side clearance is less.
• Environmentally friendly.
• Excellent capacity to support overloads.
• Reduced cost on civil installation works and fire protection
systems.
• Excellent performance in case of seismic events.
• No fire hazard.
• Excellent resistance to short circuit currents.
• Long lasting due to low thermal and dielectric heating.
• Suited for damp and contaminated areas. 13

14. Disadvantages of Dry Type
Transformer
• Dry type transformer is long lasting and with less
chance of winding failure. But once it fails whole
set up is to changed, i.e. complete change of high
voltage and low voltage winding with limb.
• For same power and voltage rating, dry type
transformer is costlier than oil cooled
transformer.
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15. Application of Dry Type Transformer
• Chemical, oil and gas industry
• Environmentally sensitive areas (e.g. water
protection areas)
• Fire-risk areas (e.g. forests)
• Inner-city substations
• Indoor and underground substations
• Renewable generation (e.g. off-shore wind turbines)
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