U
U
s
s
e
e
r
r
M
M
a
a
n
n
u
u
a
a
l
l
Revision 8.6
SECTION 6 : OPERATION OF CONTROL PANEL
87
system, if the fault persists, the problem may be related to the control box mother board, in
this case it is advisable to replace the THYROMAT unit, and send the faulty one to our
nearest repair centre.
6.8.2
Current Unbalance
Current Unbalance fault indicates that at least one of the stator phase current readings is smaller than
50% of the highest phase current reading.
6.8.2 (a)
Current unbal 1
A lower current reading occurred on stator phase 1 (i.e. CT1 input)
6.8.2 (b)
Current unbal 2
A lower current reading occurred on stator phase 2 (i.e. CT2 input)
6.8.3 (c)
Current unbal 3
A lower current reading occurred on stator phase 3 (i.e. CT3 input)
Possible causes
Motor cable faulty or bad connection
Unbalanced rotor circuit due to brush gear problems or rotor resistances faulty.
Motor with faulty stator or rotor windings
Faulty Thyristor pack, this can be measured with the use of a multi-meter, measuring the
voltage across the Input and Output of any of the devices, by comparison with the other
devices one can ascertain if there is a relevant discrepancy in readings.
A fault such as this one may be caused by a faulty Thyristor or by a faulty trigger module built into the
Phase Shifter card.
The quickest way to find out which one is the cause of the problem, is by replacing the Phase Shifter
card with another one, if the fault persists then it is likely that the problem is caused by a faulty
Thyristor pack, replace the THYROMAT unit.
Faulty Current Transformer, to identify this, the user may try to swap the C.T. inputs around to
confirm if the faulty phase reading follows the change in wiring.
Faulty THYROMAT Current Converter, the symptoms of the fault if caused by the Current
Converter unit are similar to the ones caused by the Current Transformer itself.
Note: To distinguish between the C.T. and the Current Converter, insert a meter that can read
current, in series with the C.T., circuit while the THYROMAT is in operation and compare the
reading with the readings of all the other motor phases, if there is a discrepancy at C.T. level
then replace the faulty C.T., otherwise replace the Current Converter.
It is also possible that the Control Card C.T. inputs circuit is damaged, causing the unbalance
fault. The quickest way to confirm that this is or isn’t the case is by swapping the 3 C.T. input
