Page 225 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Chart 2
Motor starts but does not share load (Runs at low speed when loaded.)

S.No Cause Test Remedy
1 Too low a voltage. Measure voltage at the motor Renew bad fuses; repair circuit and
terminals and verify it with the remove the cause of low voltage, like
name-plate. loose or bad contacts in starter,
switches, distribution box,etc.

2 Bad connection. Check the connection and contact Remove the fault as required.
of starter for loose contact.
3 Too low or high tension Measure the tension and verify it Adjust the belt tension.
on driving belt. with the instruction of the
manufacturer.
4 Open circuit in rotor Examine the rotor bars and joints. Re-solder the rotor bars.
winding.
5 Faulty stator winding. Check for continuity, short circuit Repair the circuit if possible or
and leakage. rewind the stator.
6 Defective bearings. Examine bearings for play. Replace the bearings.
7 Excessively loaded. Measure the line current of the Reduce the mechanical load on
motor and compare it with its the motor.
rated current.
8 Low frequency. Measure the line frequency with a If the line frequency is low inform the
frequency meter. supply authorities and get it corrected.

Chart 3
Motor blows off fuses
S.No Cause Test Remedy
1 Incorrect size of fuses Check the size of the fuse wire (it Replace the fuse wire if necessary;
should be rated for 1½ times its repair the motor if it is due to
normal current); connect the electrical fault of stator or rotor.
ammeter in the circuit and test for
excess load current.

2 Low voltage Measure the line voltage. Remove the cause of low voltage.
3 Excessively loaded Measure the line current and Rectify the cause of overload or install
compare it with its rated current. a motor of higher output rating.

4 Faulty stator winding Check for open circuit, short circuit Repair the fault; if not possible
or leakage of the stator as explained then rewind the stator.
earlier.
5 Loose connection in Check for loose or bad connection Rectify the loose connection; loose
starter in the starter because it may cause all the contact points of the starter
unbalancing of current. with sandpaper and align the contacts.
6 Wrong connection Check the connection with the Reconnect the motor if it still
original diagram. does not start.

212

CITS : Power - Electrician & Wireman - Lesson 93-100