2) Cleaning Slip rings
The slip ring surfaces must be uniformly bright . Slip rings showing black spots, excessive wear, or uneven wear must be repaired . A stained slip ring lowers generator efficiency and output voltage . Polish the slip rings with fine sandpaper while turning the rotor until rough spots disappear . Care should be taken not to touch the rotor coils with the sandpaper .
6-5 BRUSH
The brushes must be smooth where they contact the slip rings . If not, polish smooth the brushes with sandpaper . A brush that is not smooth produces arcs between the brush and slip ring leading to possible damage . Usable brush lengths are from 5 mm to 11 mm (0 .20 " to 0 .43") .
A brush shorter than 5 mm must be replaced because decreased contact pressure between the brush and slip ring lowers generator efficiency and output voltage .
6-6 A.V.R.
(AUTOMATIC VOLTAGE REGULATOR)
1) Features
This A .V .R . operates to control the field current in order to maintain the output voltage for the AC current, which generated by the magnetic flux by the field coil .
2) A .V .R . trouble may be identified by simply looking at the A .V .R ., or by the inter-lead resistance with a tester, or actually mounting it in the generator and operating it .
SLIP RING
BRUSH
SANDPAPER
ROTOR
BRUSH
HOLDER
5 mm
CIRCUIT TESTER
(Resistance)
- 25 -
(a) A .V .R . TROUBLE IDENTIFICATION by APPEARANCE
If an A .V .R . electronic part is burnt dark, or the surface epoxy resin melted, it often indicates
A .V .R . trouble .
(b) IDENTIFYING A .V .R . TROUBLE by CHECKING INTER-LEAD RESISTANCE
Check the inter-lead resistance of the A .V .R . with a tester, referring to the following table .
If the tester readings very greatly from the values specified in the table on next page, the
A .V .R . is faulty .
NOTE : Take tester inaccuracy into account in reading the tester.
(c) IDENTIFYING A .V .R . TROUBLE by
MOUNTING and OPERATING in THE
GENERATOR
SCR or transistor damage cannot be detected by simply looking at the A .V .R . or checking the lead resistance . Check it by mounting the suspectedly faulty A .V .R . in a normal generator, or mount a mormal A .V .R . in a generator which fails to generate voltage .
ⓐ ⓑ
②
①
④
③
AVR unit
ⓐ ⓑ
①
②
③
④
Yellow
Blue
Blue
Brown
Yellow
Yellow
ⓐ ⓑ
①
②
③
④
White
Red
Green
White
Blue
Blue
* Checking table for analogue circuit tester.
A.V.R. TYPE (A)
Apply red ⊕ needle
of the circuit tester
Yellow
ⓐ
Blue
ⓑ
Blue
①
Brown
②
Yellow
③
Yellow
④
Yellow
ⓐ
-
3 .9M
∞
∞
8 .5M
8 .5M
(R±20%)
Apply black ⊖ needle of the circuit tester (Ω)
Blue
ⓑ
Blue
①
Brown
②
Yellow
③
Yellow
④
1 .5M
∞ ∞
3 .8M
4 .3M
-
∞
∞ ∞ 2 .0M
∞
2 .1M
∞
∞
1 .7M
-
3 .4M
∞
4 .1M
-
∞
∞
-
∞
4 .3M
1 .6M
∞ ∞
4 .2M
-
* Checking table for analogue circuit tester.
A.V.R. TYPE (B)
Apply red ⊕ needle
of the circuit tester
White
ⓐ
Red
ⓑ
Green
①
White
②
Blue
③
Blue
④
White
ⓐ
-
1 .8M
4 .4M
4 .6M
4 .0M
4 .2M
Apply black ⊖ needle of the circuit tester
Red
ⓑ
Green
①
White
②
Blue
③
2 .1M
5 .0M
5 .1M
4 .6M
2 .1M
2 .1M
1 .9M
2 .0M
2 .1M
1 .7M
1 .8M
-
5 .1M
4 .5M
4 .7M
4 .9M
-
4 .5M
4 .7M
4 .4M
4 .6M
-
4 .2M
- 26 -
(R±20%)
Blue
④
4 .2M
1 .6M
4 .1M
4 .2M
3 .8M
-
