Eurotherm 590A SERIES, Product Manual

Page: 53 / 109

6 - 5
ALARM SIGNALS
The inputs to the eight input "AND" gate are:
1) PRESET BOARD: The Preset board is electrically interlocked. In the event of its removal or
absence the drive is quenched and Indicator 1 is extinguished (Note: removal of the preset board whilst the
drive is operating is not recommended).
2) 3-PHASE PRESENT: To ensure that all three phases of the incoming supply are present and of
sufficient amplitude, a detection circuit utilising an optoisolator produces a logic level indication. This also
detects the loss of any of the supply or suppression fuses FS2-FS4. Indicator 3 will extinguish if these
requirements are not satisfied.
3) FIELD FAILURE: In the event of Field Failure (when the field current drops below 110mA) or if
the field supply or fuses FS3 and 4 and are lost the output from the field detection circuit falls (Diagnostic 7)
and the drive is quenched.
4) P.L.L. SYNCHRONISATION: To ensure that the 3-Phase supply to the drive lies in the range 45-
65Hz. Indicator 2 illuminates when synchronisation is complete.
5) THERMISTOR/MICROTHERM: It is good practice to protect DC motors against sustained thermal
overloads by fitting temperature sensitive resistors in the field and interpole windings of the machine. These
devices have a low resistance (typically 200 Ohms) up to a reference temperature (125
°
C) and above this their
resistance rapidly increases to about 2 Kilohms. They should be wired in series and connected between 0 volts
and the thermistor input (terminal 29). A sensing circuit within the drive detects the change in resistance and
produces a high logic level (Diagnostic 6) provided the resistance is low. The signal drops if the motor
temperature exceeds 125
°
C and thereby quenches the drive.
NOTE : This method of stopping the drive does not operate the three phase isolating contactor, it only phases
back the firing pulses to give zero DC output to the armature. THE DRIVE MAY RESTART
AUTOMATICALLY WHEN THE MOTOR TEMPERATURE FALLS. Never work on the drive, motor,
or ancillary equipment without first isolating the main supply.
Note: see terminal description 30 and option switch S8/5 which can be used to prevent the drive operating
again when the motor temperature has fallen.
7) AUXILIARY ENABLE: Terminal 30 on the drive is normally connected to +24 volts at Terminal
31 to enable the drive to run. Alternatively may be connected to +24 volts at Terminal 37 if latching of the
Thermistor/microtherm, Field failure and external interlock alarms is required. Removing the signal from
Terminal 30 will quench the drive.
NOTE: That this method of stopping and starting the drive does not operate the three phase isolating contactor,
it only phases back the firing pulses to give zero DC output to the armature. It should only be used for shot term
stops and never used if an operator can work on the motor or ancillary equipment without tripping the contactor
and locking off the supply isolator.
8) START INSTRUCTION: The Start/Stop instruction is applied through terminal 31 via the external
Start/Stop wiring. During the stop sequence, it is essential that the motor armature current is reduced to
zero before the 3-phase isolating contactor is opened. This is achieved in the drive at switch off by a time delay
(of approximately 30ms) before the contactor control relay is de-energised.
The start supply is taken from terminal 34 which is no24 volts. If excessive armature current
levels are detected (400% for 3ms) an instantaneous latching trip is operated. (refer to option switch S8/7 )This
trip can be arranged to de-energise the contactor, thus isolating the 3 phase supply. Reset of the overcurrent trip
can only be achieved by removing the start instruction and operating the fault reset push button or by applying
+24V to terminal 39 through a momentary closed contact.
Only when all eight alarms are present is the Ready Output (Terminal 35) switched to +24 volts.
This manual was downloaded on www.sdsdrives.com
+44 (0)117 938 1800 - info@sdsdrives.com