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 TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
Table 11-2. Doubleshooting chart for general control equipment (continued)
Trouble
Cause
Course of
MAGNETS AND OTHER ME-
CHANICAL PARTS:
1. Contacts slam in caused by: overvoltage,
Worn or broken parts
Replace part and correct cause of damage.
underload, wrong coil. Chattering caused by:
NOTE: The mechanical life should be mea-
broken pole shader or poor contact in control
sured in number of operations.
circuit. Heavy duty cycle. Too much jogging.
Abrasive dirt, mechanical abuse.
Noisy magnet.
1. Broken pole shader, magnet faces not true
Replace.
(result of wear or mounting strains).
(For locations where the ac hum is objection-
able, use dc magnets. Hum can be reduced by
mounting on rubber or springs.)
2. Dirt or rust on magnet faces..
Clean magnet.
3. Low voltage. . . . . . . . . . . . . . . . . . . . , . . . . . . . .
Check system voltage.
Broken pole shader
1. Contacts slam in caused by: overvoltage,
Replace and correct the cause.
magnet underloaded, weak tip pressure,
wrong coil.
SLIDING CONTACTS:
Abrasion . . . . . . . . . . . . . . . . . . . . . . .
1. Lack of care and lubrication; very heavy
Sliding contacts usually require lubrication.
roughening of contacts
service; arcing; oxidation; abrasive dirt..
(Use lubricant recommended by manufacturer.)
Special alloy contacts should be specified for
extra heavy service.
Arc.............................
1. Abnormal interrupting duty such as induc- Check application.
tive loads, excess vibration, or shock..
NOTE: On severe-duty applications, arc chutes
wear out and must be replaced periodically.
2. M o i s t u r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Eliminate presence of moisture. Keep several
chutes on hand for replacement.
See manufacturer's instruction sheet.
3. Improper assembly..
4. Rough handling.
Replace.
Drum switches, rheostats, knife
1. Overcurrent; low contact pressure; oxida-
For very heavy service, use special alloy con-
switches overheating.
tion; high ambient; rough contacts..
tacts. Lubricate periodically as manufacturer
recommends.
Insulation failure
1. Overvoltage, voltage transients, high in-
Correct system voltage and conditions. Use
discharge resistors where needed.
duced voltages, moisture.
2. Mechanical damage..
Replace damaged parts. Correct condition.
3. Moisture, dirt and fumes, overheating (car- Keep controls clean and dry. Get special coil
for application.
bonizing).
Failure to pick up.
1. Low voltage on coil.
Check system voltage.
2. Coil open, wiring of coil or shortened
Replace.
turns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3. Wrong coil.
Check manufacturer for recommendations.
4. Excessive magnet gap, magnet overloaded. Check instruction sheet and adjust.
Failure to drop out magnet-
Check instruction sheet, and adjust.
1. Mechanical binding.
operated device
2. Gum or dirt on magnet faces.
Clean.
3. Worn bearings
Replace the part.
4. Nonmagnetic gap in magnetic circuit de-
Replace magnet.
stroyed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5. Contact tip welded
Use other contact material.
6. Voltage not removed.
Check coil voltage.
7. Not enough mechanical load on magnet,
Check instruction sheet, and adjust.
improper adjustment.
OVERLOAD RELAYS:
Magnet-operated instantaneous-
1. Wrong coil.
Install coil with correct rating.
type, high trip or low trip.
2. Shorted turns (on high trip).
Test coil and replace if found defective.
3. Mechanical binding; dirt, corrosion, etc..
Clean parts with suitable solvent.
4. Assembled wrong..
See manufacturer's instruction sheet.
5. Wrong calibration.
Refer to manufacturer.
1. Fluid too viscous, vent too small, or tem-
Magnet-operated inverse-time
Change fluid and open vent slightly, or regu-
type, slow type. .................
perature too low
late temperature.
2. Mechanical binding; dirt corrosion, etc.
Clean parts with suitable solvent.
Replace and adjust.
3. Worn parts
Fast trip
1. Worn or broken parts.
Replace.
11-10
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