1. Instrument Connection
1.1 Physical
The SML 133 instrument is built in a plastic box to be installed in a distribution board panel. The instrument’s position must be
fixed with locks.
Natural air circulation should be provided inside the distribution board cabinet, and in the instrument’s neighbourhood,
especially underneath the instrument, no other instrumentation that is source of heat should be installed or the temperature
value measured may be false.
1.2 Power Supply
The supply voltage (in range according technical specifications) connects to terminals AV1 (No. 9) and AV2 (10) via a
disconnecting device (switch – see wiring diagram). It must be located at the instrument’s proximity and easily accessible by
the operator. The disconnecting device must be marked as such. A two-pole circuit breaker with the C-type tripping
characteristics rated at 1A makes a suitable disconnecting device, its function and working positions, however, must be
clearly marked. A connection cable maximum cross section area is 2.5 mm
2
.
In case of DC supply voltage the polarity of connection is generally free, but for maximum electromagnetic compatibility the
grounded pole should be connected to the terminal AV2.
1.3 Measured Voltages
The phase voltages measured are connected to terminals U1 (12), U2 (13), U3 (14), the common terminal to connect to the
neutral wire is identified as N (11; it stays free at delta- (3D) and Aron- (3A) connections). It is suitable to protect the voltage
lines measured for example with 1A fuses. Measured voltages can also be connected via instrument voltage transformers.
A connection cable maximum cross section area is 2.5 mm
2
.
1.4 Measured Currents
The instruments are designed for indirect current measurement via external CTs only. Proper current signal polarity (S1, S2
terminals) must be observed. You can check the polarity by the sign of phase active powers on the instrument display (in
case of energy transfer direction is known, of course).
The current signals from 5A or 1A (or 0.1A for the „X/100mA“ models) instrument current transformers must be connected to
the terminal pairs I11, I12, I21, I22, I31, I32 (No. 1 ÷ 6). In the P.01 parameter (see below), set the CT-ratio.
The I2 terminals stay free in case of the Aron connection.
A connection cable maximum cross section area is 2.5 mm
2
.
