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2.4
Undercurrent.
Single phase relay PS
The setting of the underload trip level is made using a potentiometer in wich
a factor between 0,4 and 0,9 is to be chosen. By multiplying this factor by
the adjusted
,
B
we obtain a current value under which the relay will trip and
disconnect the motor. The trip is delayed by 5 seconds.
a) If the value of the
,
B
of the motor without load is known:
• To avoid unwanted trips it is recommended to adjust the value 15%
above the
,
B
of the motor without load.
Example:
b) If the value of the
,
B
of the motor without load is unknown:
• If the pump is adequately dimensioned, the recommended value for
this factor is 0,7. Adjust the potentiometer “undercurrent” to 0,7.
• If the pump is excessively dimensioned, and during its operation
unwanted trips could occur, the underload adjusted factor should be
reduced to approximately 0,6.
Three phase relay P
The undercurrent trip level in P relays is set using three dipswitches. To
avoid nuisance trips, set this level to approximately 10% above the no-load
motor current.
Example:
2.5
Phase sequence
Monitoring the current. GL and P relays
An incorrect phase sequence is detected by current sensing and it is only
operative during the motor start-up. For correct detection the starting time
must be longer than 0.2 s.
In GL relays the user can activate or desactivate this protection by means
of a dipswitch. Should the right phase sequence be critical, move the
dipswitch to the “ON” position. If this protection is not required, always leave
it in the “OFF” position.
As this function is not compatible with the use of frequency inverters, where
it is necessary to protect phase sequence in these installations, move the
dipswitch to “OFF” and install the Fanox “S” model relay.
Monitoring the voltage. PF relays
An incorrect phase sequence is detected by voltage monitoring.
In the event that an incorrect phase sequence has been detected, the
motor will not start-up since the relay has tripped because of previously
detecting the wrong phase sequence.
• Dry running
• Dry running
0.6 x 1.1 = 0.66
x1.1
