Troubleshooting and Maintenance of Square D Motor Control Equipment
WARNING: There is a hazard of electric shock or burn whenever working on or around electrical equipment. Turn
off power supplying this equipment before working inside motor control centers
Motor Control Trouble-Remedy Table
-.-2 The following table lists troubles encountered with
motor control, their causes and remedies This table is of
a general nature and covers only the main causes of
Misapplication of a device can be a cause of serious
trouble, however rather than list this cause repeatedly it
should be noted here that misapplication Is a major
cause of motor control trouble and should always be
questioned when a device is not functioning properly.
Actual physical damage or broken parts can usually be
found quickly and replaced. Damage due to water or
flood conditions requires special treatment. Contact your
local Square D office.
Poor contact in control circuit.
1. Replace the contact device or use holding circuit (Also
see interlock (3 wire control).
2. Check coil terminal voltage and voltage dips.
Abnormal inrush of current.
1. Check foregrounds, shorts, or excessive motor load
current, or use larger contactor.
2. Install larger device rated for jogging service.
Insufficient tip pressure.
3. Replace contacts and springs, check contact
carrier for deformation or damage.
Low voltage preventing magnet from
4. Check coil terminal voltage and voltage dips
Welding or Freezing
Foreign matter preventing contacts from
5. Clean contacts with Freon Contacts, starters, and
control accessories used with very small current or
low voltage, should be cleaned with Freon.
Short circuit or ground fault.
6 Remove fault and check to be sure fuse or breaker size
Filing or dressing.
1. Do not file silver tips Rough spots or discoloration will
not harm tips or impair their efficiency.
Interrupting excessively high currents.
2. Install larger device or check for grounds, shorts, or
excessive motor currents.
3. Install larger device rated for jogging service.
Weak tip pressure.
4. Replace contacts and springs, check contact carrier
Short Tip Life or
for deformation or damage entry of foreign matter into
Overheating of Tips
Dirt or foreign matter on contact surface.5
Clean contacts with Freon Take steps to reduce
Short circuits or ground fault.
6. Remove fault and check to be sure fuse or breaker size
Loose connection in power circuit.
7. Clear and tighten.
8. Check for excessive motor load current or install larger
1. Handle and store coils carefully.
Over voltage or high ambient tempera-
1. Check coil terminal voltage which should not exceed
110% of coil rating.
2. Install correct coil.
Shorted turns caused by mechanical
3. Replace coil.
damage or corrosion.
Under voltage, failure of magnet to seal.
4. Check coil terminal voltage, which should be at
Dirt or rust on pole faces.
5. Clean pole faces.
6. WITH POWER OFF check for free movement of contact
and armature assembly.