INSTALLATION GUIDE
MODULAR SUNWAY TG
TE OD
Rev. 03
– 01/06/2018
57/
139
Secondary Voltage
V
Based on inverter AC output voltage
Primary Tapping Voltage Range
(+2) (-2) x 2.5% (Suggested)
Primary/Secondary Connection
Delta/Star
Secondary Neutral Terminal
Not required for inverter operation. It must not
be connected to earth.
Primary Testing Voltages: Um/imp
kV
According to applicable standards
Induced voltage test - Secondary
kV
According to applicable standards
Applied voltage test - Secondary
kV
3 for transformers applied to 1000V inverters
4 for transformers applied to 1500V inverters
Short-Circuit Impedance (at 75°C) pri/sec
%
6% (+/- 10% tolerance)
Short-Circuit Mutual Impedance sec/sec
(in case of double-wound transformer)
%
8% (+/- 20% tolerance)
Maximum difference between short-circuit
impedance sec1/prim and short-circuit
impedance sec2/prim (*)
%
10%
Electrostatic shield
Yes. Shield must be earthed.
Table 11: Transformer technical requirements
(*) For example, if the SC impedance between sec1/pri is 6%, the impedance between sec2/prim may range
between 5.4 and 6.6%.
6.4.4.2. Transformer application requirements
The transformer shall be designed to work at rated power according to specific application requirements.
Because it is connected to an inverter power supplied by a PV field, stress to the winding isolation in respect
to the earth potential is much more severe.
A 500V/µsec dU/dt between secondary windings and the earth is present. The secondary windings shall be
tolerant for pulsed waveforms of up to +/- 1500V or 2100 V to earth for PV fields with open-circuit voltage
up to 1100 V or 1500 V respectively.
The transformer shall operate with a maximum THD current generated by the inverter at full power equal to
3%.
If a double winding transformer is used, the transformer must be capable of operating with only one live
secondary.
6.4.4.3. Application requirements of the transformer
In general, it is recommended that the transformer has a number of windings equal to the number of
independent MPPTs implemented into the chosen inverter configuration by connecting each winding to the
AC output corresponding to each MPPT.
The AC outputs corresponding to the DC sections utilized in separate MPPTs may be connected in parallel
to the same winding only provided that the dedicated option be installed (see 8.10) and the application be
approved. Please contact Elettronica Santerno SpA.
It is also advisable that y/D configuration (inverter-side star) is adopted for the transformer. In that case, the
neutral must not be earthed.
In case a double secondary transformer is chosen, a transformer configuration either with concentric
windings (LV, MV, LV) or with four windings (double tier) is recommended.
MPPT
Secondary
