Eurotherm 590A SERIES, Product Manual

Page: 45 / 109

5 - 3
to flow. The maximum level of this signal is later modified by the Current Limit circuit (according to the input
voltages at terminals 22,23 and 25) before comparison with the Current Feedback signal
21. SELECT AUXILIARY CURRENT INPUT*
If this Terminal is connected to 0V any input at terminal 20 will be connected through to the input of
the Current loop and will be added to the Current Demand Signal (see also Current Demand Isolate, Terminal
18). In Speed Control applications Terminal 21 is normally left open circuit.
22. AUXILIARY CURRENT LIMIT (+) POSITIVE *
This input provides independent control of the positive Armature current limit, from zero up to the
maximum allowed by the Main Current Limit setting (see terminal 23 description). If this facility is not required
Terminal 22 should be left open circuit, in which case Auxiliary Current Limit (+) is disabled by an internal pull-
up resistor and control reverts to the Main Current Limit.
The control voltage range at Terminal 22 is 0 to +10V = 0 to +200% Full Load Current. The input
impedance is approximately 25K Ohms. Because of the internal pull-up resistor adjustment of the terminal
voltage can be made by an external resistor connected between 22 and 0V. Alternative methods of control are a
potentiometer (ends connected to 24 and 0V, wiper to 22) or an analog voltage in the range 0 to +10V. Negative
voltage MUST NOT normally be applied to this input.
23. MAIN CURRENT LIMIT
The Main Current Limit provides symmetrical control of both positive and negative Armature current
limits. If different positive and negative current limits are required see 22 and 25 when external control of the
Main Current Limit is not required 23 should be connected to +10V (Terminal 24). The input voltage at
Terminal 23 supplies the Main Current Limit preset potentiometer P7, thus the actual current limit value
depends upon the voltage at 23 and the setting of P7. Assuming that P7 is set fully clockwise, the control
voltage range at Terminal 23 is 0 to +10V = 0 to +/-200% Full Load Current (0 to +200% Full Load Current in
the case of 591A and 599A controllers). A negative input voltage MUST NEVER be applied to this Terminal.
24. +10V PRECISION REFERENCE
Setpoint reference supply. This supply is short-circuit proof but for normal operation the load on
Terminal 14 plus Terminal 24 should not exceed a total of 5mA.
25. AUXILIARY CURRENT LIMIT (-) NEGATIVE *
This input provides independent control of the negative Armature current limit, from zero up to the
maximum allowed by the Main Current Limit setting (see terminal 23 description). If this facility is not required
(and in all 591A and 599A applications) Terminal 25 should be left open circuit, in which case the Auxiliary
Current Limit (-) is disabled by an internal pull-up resistor and control reverts to the Main Current Limit.
The control voltage range at Terminal 25 is 0 to -10V = 0 to -200% Full Load Current. The input
impedance is approximately 25K Ohms. Because of the internal pull-up resistor adjustment of the Terminal
voltage can be made by an external resistor connected between terminal 25 and 0v. Alternative methods of
control are a potentiometer (ends connected to 15 and 0V, wiper to 25) or an analog voltage in the range 0 to -
10V. Positive voltages MUST NOT normally be applied to this input.
26. BUFFERED TACH OUTPUT
This output has the same polarity as the Tach input voltage on Terminal ( 1&2 for AC Tachs, or 3, or
17, for DC Tachs) but is attenuated so that 0 to +/-100% Full Speed is represented by an output of 0 to +/-10V.
The output is short-circuit proof and may be used to supply speed indicator or speed sensing circuits up to a
maximum load current of 5mA.
27. BUFFERED CURRENT OUTPUT
This output is short-circuit proof and may be used to supply Armature current Indicators or sensing
circuits up to a maximum load current of 5mA. Modulus or Bipolar outputs are available depending upon the
setting of Option Switch S8/1. For centre-zero indicators S8/1 should be ON (UP) so that the output is Bipolar
i.e. positive and negative Armature currents are represented by positive and negative outputs at Terminal 27.
For end-zero indicators S8/1 should be OFF (DOWN) so that the output represents the Modulus of the
Armature current i.e. both positive and negative Armature currents are represented by a positive output at
terminal 27. In either case an output of 10V represents an Armature current of 200% Full Load, 5V represents
100% Full Load Current etc. In 591A and 599A applications the setting of S8/1 is immaterial since these units
only produce positive Armature current.
This manual was downloaded on www.sdsdrives.com
+44 (0)117 938 1800 - info@sdsdrives.com