SMY133-SMY134-SMP133 Operating Manual
2.3.4.2 Voltage Type Current Inputs Instruments ( Models
„X/333mV“ )
The instruments are equipped with separate connectors for particular measuring current input. Each
connector has three terminals. Function of the terminals is described in following table :
“X/333mV“ Models Current Inputs Connection
terminal No.
signal
62
SI1 … signal corresponding to I1 current (in phase L1), CT terminal “S1”
65
SI2 … I2-S1 (phase L2)
68
SI3 … I3-S1 (phase L3)
63, 66, 69 SG …common pole of the I1 ÷I3 signals (CT terminals “S2”) and negative pole of the
5V built-in auxiliary power supply for current sensors (the terminals are
interconnected)
61, 64, 67 SP... positive pole of the 5V built-in auxiliary power supply for current sensors (the
terminals are interconnected)
The instruments are designed for cooperation with current transformers with output nominal voltage of
333 millivolts. They can be also used with flexible current sensors (Rogowski coils) with embedded
integrator of appropriate voltage output signal.
The CTs must be connected with two-wire twisted cable. Again, proper current signal polarity (CT
secondary terminals S1, S2) must be observed.
Recommended wire type : twisted pair, for example KU03G24 ( Nexans )
Recommended minimum conductor cross-section: 0.2 mm
2
Maximum conductor cross-section: 1.5 mm
2
Maximum length of the cable is 3 metres !
The flexible current sensors with embedded integrator usually require a power supply. For such
purpose the instruments are equipped with auxiliary power supply 5V. Maximum load of each sensor
connected is 20 mA.
Connection of standard CTs with 5A or 1A nominal output current to the „X/333mV“
instruments s
forbidden
!!! Otherwise the instrument can be damaged !!!
2.3.5 Other Inputs/Outputs
Connection of residual current inputs, other inputs, outputs and communication links are described in
appropriate chapters further below.
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