Insulation

Question 1

Class O

Answer 1

90*C
Cotton, silk, paper, similar organic materials
Neither impregnated nor immersed in a liquid dielectric

Ex - main/pilot exciter shunt field & insulating windings

Question 2

Class A

Answer 2

105*C
Cotton, silk, paper, similar materials
Impregnated or immersed in a liquid dielectric
-molded and laminated materials with cellulose filler, phenolic resins, and other resins of similar properties
- Films and sheets of cellulose acetate and other cellulose derivatives of similar properties
- enamel varnishes as applied to conductors

Ex - main XFMR, gen field, main/pilot exciter commutator

Question 3

Class B

Answer 3

130*C
Mica, asbestos, fiberglass & similar inorganic materials in built-up form with organic binding substances
small portion of class a may be used for structural purposes only

Ex - ss xfrm, lighting xfrm, stator (epoxy), nb xfrm

Question 4

Class F

Answer 4

155*C
Mica, asbestos, fiberglass, dacron glass & similar inorganic materials, or combinations of these material with suitable bonding, impregnating, or coating substances (not necessarily inorganic)

Ex - wh xfrm

Question 5

Class H

Answer 5

180*C
Mica, asbestos, fiberglass & other similar inorganic materials in built-up form with binding substances composed of silicone compounds or materials with substances composed of silicone compounds or materials with equivalent properties.
Silicone compounds in rubbery or sesinous forms or materials with equivalent properties
A minute proportion of class a materials may be used only where essential for structural purposes during manufacture

Ex - none

Question 6

Class C

Answer 6

No Limit
Mica, porcelain, glass quartz and similar inorganic materials

Ex - current limiting reactor