Single Phase String Inverters - Power-One

SINGLE PHASE STRING 

INVERTER WEBINAR 

AURORA® ACADEMY 

1

Training Objectives 

Power-One Residential Product Overview 

UNO/PVI Series 

• Key advantages and specs 

• Design 

• String Sizing 

• Single/Dual MPPTs 

• Isolated and Transformerless 

• Grounding methods 

• Installation and Configuration 

General Trouble Shooting 

2

Product Mapping 

 

UNO-7.6-TL 

UNO-8.6-TL 

 

Residential Segment 

 

 

Commercial Segment 

 

Utility Segment 

 

 

3

Single Phase String Inverters Overview 

From 2 kW to 6 kW 

Product Series Uno PVI-TL PVI-I PVI-TL 

Sizes 2, 2.5 kW 3, 3.6, 4.2 kW 3.8, 4.6 kW 5, 6 kW 

Isolation Isolated Transformer-less Isolated Transformer-less 

Integrated DC 

Disconnect 

NEMA 4X 

 

 

 

 

 

 

 

 

4

Single Phase String Inverters Overview 

Micro 

String 

250W / 300W 

ISOLATED 

NEMA 4X 

2KW / 2.5KW 

ISOLATED 

NEMA 4X 

3KW / 3.6KW / 4.2kW (- 

S) 

Transformerless 

w/DC Switch 

NEMA 4X 

3.8KW / 4.6kW (-S) 

ISOLATED 

w/DC switch 

NEMA 4X 

5KW / 6kW (-S) 


w/DC Switch 

NEMA 4X 

Single MPPT 

Dual MPPT 

5

UNO-2.0/2.5-I-OUTD-US 

Single Phase 

HF - Transformer 

String Inverters

Higher Efficiency & Faster Installation 

High Efficiency 

• 97.5% CEC Efficiency; Operating near peak 

efficiency regardless of output power 

• MPPT Efficiency is >99% across entire input 

range & majority of power output conditions 

Faster Installation 

• Integrated DC Disconnect switch & wiring box 

• Lifting cover for easy access to connection area 

• Installer friendly wall connection system 

9

10 

Highly Reliable Design

Innovative Thermal Design 

Structure: the front cover has 

three layers. An external cover, a 

thermal insulator and a die-cast 

aluminum layer. 

The profile of the die-cast cover 

with the opening at the top and 

bottom creates a “chimney 

effect” and an “air cushion” 

which improves thermal 

insulation. 

If the inverter is exposed to 

direct sunlight, the thermal 

insulator and “air cushion” 

reduce heat transfer to the 

internal enclosure enabling more 

reliable energy harvest(*). 

(*) Real world tests demonstrate this 

solution reduces inverter internal 

temperature by 8°C when the cover is 

subjected to direct solar irradiation. 

11

UNO-2.0/2.5-I-OUTD 

Mechanical Characteristics: installer-friendly construction 

• Easy and quick installation thanks to the “T” mounting 

bracket. 

• The cover can be opened by lifting it up to access to 

the wiring compartment. 

12


Switch Box Can Be 

Mounted Separately 

13


Neg / Pos 

Ground Connection 

AC Grid 

Adjustment 

DC Terminal 

Block 

Com Board 

RS 485 

GFD Fuse 

AC Terminal 

Block 

DC Disconnect 

14

NEW Graphic Display 

Active communication 

ports 

Graphic 

representation of 

produced power 

Actual power 

“Classic” 2x16 

digits display: 

statistics, info, 

settings 

Daily energy and total 

energy harvesting 

The display functionalities and the 

communication capabilities are 

continuously available: the inverter 

is powered by the grid (stand-by 

consumption

UNO-2.0/2.5-I-OUTD : configuration 3/5 

Field configuration of inverter for PV array grounding 

NG 

Grounding of the Negative DC 

Terminal (Default) 

16

UNO-2.0/2.5-I-OUTD : configuration 4/5 

Field configuration GROUNDING of inverter OF DC INPUT for PV array grounding 

PG 

Grounding of the Positive DC 

Terminal 

17

UNO-2.0/2.5-I-OUTD : Installation 

Installation position 

Multiple installations 

18

PVI-X.X – Series 

Single Phase 

I – High FrequencyTransformer 

and 

TL - Transformerless

Product Portfolio: Grid-Tied PV Inverters 

Residential 

Light Commercial 

3KW / 3.6KW / 4.2kW 


NEMA 4X 

3KW / 3.6KW / 4.2kW (-S) 


w/DC Switch 

NEMA 4X 

3.8KW / 4.6kW (-S) 

ISOLATED 

w/DC switch 

NEMA 4X 

5KW / 6kW (-S) 


w/DC Switch 

NEMA 4X 

10KW / 12kW (-S) 

ISOLATED 

TRUE 3-PHASE 

w/DC Switch 

NEMA 4X 

UL 1741/IEEE 1547/CSA22.2#107.1-01 

20

Single-Phase String Inverters: Key Advantages 

21 

Profitable 

• High CEC Efficiency 

• Fast Installation – Integrated DC Disconnect 

Dependable 

• Convection Cooling removes failure points 

• NEMA 4X Enclosure Rating 

Flexible 

• Dual independent MPPT 

• Wide DC input voltage window 

Connected 

• Equipped with Aurora Vision Monitoring 

• Wireless monitoring solution

Switch Box Design Change Summary 

• Power-One is introducing a Product Design Change to the 

following String Inverters 

o 

o 

o 

o 

o 

PVI-3.0-OUTD-S-US 



PVI-5000-OUTD- US 

PVI-6000-OUTD- US 

• The DC disconnect switch will be moved to the front of the DC 

switch wiring box 

• Front facing Switch offers higher visibility and easier access to the 

DC disconnect switch 

• Wiring Terminals will be changed from the screw-type to pressure 

clamp type – MAINTENANCE FREE 

22

Switch Box Changes for PVI- X.X-TL-OUTD 

SWITCH BOX APPEARANCE 

OLD DESIGN 

NEW DESIGN 

Models Affected: 

PVI-3.0 

PVI-3.6 

PVI-4.2 

PVI-5.0 

PVI-6.0 

23

TL WIRING BOX CHANGES 

No P/N Change 

No Functional Change 

OLD DESIGN 

NEW DESIGN 

24

Selecting the Inverter 

• String Sizing & the Power-One Inverters 

• Strings do not need to be equal when connected to Power-One Inverters. 

• Two separate MPPT channels for different tilts and different number of 

modules in each string. 

• Double verify max amperages and voltages of string design 

25

Industry Leading MPP Tracking 

Dual MPPT Channels 

Dual independent MPPT channels for 

improved design flexibility 

Mpp1 

Mpp2 

Operates as a single channel for two 

independent channels 

Responsive & Accurate MPPT 

Shade resistant - Algorithm scans the 

whole input voltage range looking for the 

real MPP 

MPP seek time

27 

Array & String Sizing 

http://stringsizer.power-one.com/

Advantages of Dual MPPTs 

N 

MPPT #1 MPPT #2 

28 

EACH AURORA INVERTER COMES STANDARD WITH 2 SEPARATE MPPT CHANNELS 

FOR DIFFERENT ORIENTATIONS- IT'S LIKE HAVING 2 INVERTERS IN ONE!

Dual Independent MPPT: High Design Flexibility 

It is like 2 Inverters in 1! 

‒ Fully independent MPPs are managed separately for improved energy harvest 

Dual independent MPPT channels for improved design flexibility 

MPPT #1 

1 String of 

10 modules 

MPPT #2 

2 Strings of 

10 modules 

29

Power One Distinctive Product Differentiators 

Rugged NEMA 4X Construction 

• The only true outdoor string inverter available on the market 

with waterproof NEMA 4X casing for unrestricted and maintenancefree 

use in hostile environments 

5 KW 

6 KW 

Extended Temperature Range 

• True convection cooling system and thermal design to assure full 

power operation at or above 50°C. 

• Low temperature operation down to -25°C 

(storage temp. -40°C) 

Reliability 

• Reduced number of electrolytic capacitors 

• Free convection cooling design 

• Watertight IP65/NEMA4X enclosure 

3.0 KW 

3.6 KW 

4.2 KW 

3.8 KW 

4.6 KW 

ISOLATED 

30

Aurora PV String Inverters 

LCD Display and Key PAD 

• LED’s 

• LED1 Power 

• LED2 ALARM 

• LED3 GFI 

• Display Key Operation: 

• UP / DOWN keys scroll through items. 

• ESC key return to the previous screen. 

• ENTER to open the selected submenu. 

31

Aurora Solar String Inverters…Isolated 

• Isolation 

• ISOLATED INVERTERS have an internal isolation transformers , 

which provide galvanic isolation 

• TRANSFORMERLESS INVERTERS do not have (or need) galvanic 

isolation between input and output 

3.8KW / 4.6kW (-S) 

ISOLATED 

w/DC switch 

NEMA 4X 

10KW / 12kW (-S) 

ISOLATED 

TRUE 3-PHASE 

w/DC Switch 

NEMA 4X 

32

Aurora Solar String Inverters…Transformerless 

Transformerless (-TL) vs. Isolated: What are the differences 

(1) -Efficiency 

• TL Inverters are more efficient than Isolated Inverters because they 

do not have losses associated with an isolation transformer. 

3KW / 3.6KW / 4.2KW 


NEMA 4X 

3KW / 3.6KW / 4.2KW (- 

S) 


w/DC Switch 

NEMA 4X 

5KW / 6KW (-S) 


w/DC Switch 

NEMA 4X 

33

Aurora Solar String Inverters 

Transformerless vs. Isolated: What are the differences 

(2) Panel Choices 

• TL Inverters 

• All solar modules must be provisioned with double insulated 

lead wire per UL4703, or “PV wire” per NEC 

• Cannot support solar modules requiring positive grounding , 

e.g., Sunpower, and Thin Film Technology 

• Isolated Inverters support all panel types 

(3) Weight 

• Transformerless Inverters – contain no heavy transformer 

• Power-One Isolated inverters utilize light-weight, HF (18kHz) 

transformers 

• 60 Hz TF weighs roughly 5 times more than a HF 18 kHz xfmr. 

34

Aurora Solar String Isolated Inverters 

Example: HF vs. LF weight and CEC efficiency 

(HF) Power-One 4.6kW = 

61 lbs, CEC 96% @ 208 Vac / 96.5% @ 240V/277 Vac 

VS. 

(LF)PVP 4.6kW = 100 lbs heavier 

162lbs, CEC 95.5% @ 208 Vac 

35

Aurora Solar String Inverters…Transformerless 

• Wiring methods – 

• Separation of NEG (-) conductor from Grounding conductor 

• (No Grounded System Conductor) 

• NEC Article 200 (Grounded Conductor Identification) 

• NEC Article 250 (Grounding Conductor Identification) 

• Lightning Protection – 

• MOV/SOV – UL Listed Recognized 

• Gas Actuated - Inert Gas =Poor Conductor, voltage surges 

ionize the gas, making it a very effective conductor. It passes 

on current to the ground line until the voltage reaches normal 

levels, and then becomes inert again. 

36

Grounding Methods 

DC - 

DC + 

Isolated 

Inverter 

AC 

SES 

Grid 

In an transformer based inverter, there is a bond 

between ground and the grounding conductor. In this 

example the grounding conductor is the negative pole. 

DC + 

DC - 

AC 

SES 

Grid 

TL 

Inverter 

37

38 

Mounting The Inverters

Aurora PVI-X.X - 1Ø String Inverters 

Do not mount the AURORA Inverter where exposed to direct sun radiation 

or any other heat source. When the ambient temperature rises above 

113°F/ 45°C the inverter may self-derate the output power. For full power 

of AURORA Inverter (no derating), be sure the airflow through the heat 

sink is clear. Blockages will result in less than expected power output.

Mounting The Inverters 

The Choice of the Place of Installation – Outdoor Versions 

40 

•The IP65 protection level allows outdoor installation: 

•Direct solar radiation protection is recommended! (Mount on North side of exterior) 

•The natural convection cooling mechanism requires good air circulation around 

the unit 

Pay attention to passing clearance! 

Pay attention to the mutual position of the inverters!

41 

Mounting The Inverters


• Film instead of electrolytic 

capacitors on DC power bus: usable 

life extended to 30 years. 

•High immunity to input surges: 

robust structure and immune to 

transient surges produced by indirect 

discharges or bad contacts on the 

photovoltaic generator. 

•Input voltage up to 1000Vdc to 

optimize the configuration 

All Power-One Inverters Utilize Film 

Capacitors - ELECTROLYTIC-FREE! 

42 

42


Dual MPPT DC Wiring Method (older versions) 

(Connection shown for product versions without integral DC switch) 

• Remove four cover screws 

• Connect DC Cable for Individual MPPT tracking Note: 

• Select switch S1 to IND (independent) setting The Dual MPPT connection 

shown is not available on 

Isolated Inverters models when 

connected to a positively (+) 

grounded array. 

43


Dual MPPT DC Wiring Method (NEWER versions) 


• Connect DC Cable for Individual MPPT tracking 

• Select switch S1 to IND (independent) setting 

S1 switch is located 

in the upper 

enclosure of the 

inverter 

44


Single MPPT DC Wiring Method 

• Remove four cover screws 

• Connect DC Cable for Parallel MPPT tracking 

• Select switch S1 to PAR selection 

• Jumpers are used in specified applications when strings are combined on 

the roof 

45


Dual MPPT DC Wiring Method (NEWER versions) 


• Connect DC Cable for Individual MPPT tracking 


S1 switch is located 

in the upper 

enclosure of the 

inverter 

46


Complete Inverter Wiring Cabling 

(Shown for product versions without integral DC switch) 

INPUT CABLE 

OUTPUT CABLE 

ALARM CABLE 

GROUND CABLE 

RS485 CABLE 

47


Complete Inverter Wiring Cabling with (older) Switch Box 

Switch box 

Input Terminals 

Note: 4- terminal Input 

block is not rated for 

multiple wires – only 

one wire per terminal 

is allowed by NEC 

Switch box 

Grid Terminals 

48

Aurora PV ISOLATED String Inverters 

3.8kW & 4.6kW Grid Voltage Configuration 

Left selector Right selector Grid standard Display language 

0 0 Default North America 

0 2 UL - 208 Single Phase North America 

0 3 UL - 240 Split Phase North America 

0 4 UL - 277 Single Phase North America 

You have 24 hrs to change this setting! 

49


Output Functions: Grid Connections II: Single Phase Output 

Various GRID connections are easily programmed via the front panel 

KEY PAD or a laptop and with supplied software. 

Available configurations are shown below: 

2 

L1 

1 

Aurora 

240V Split Ø 

L1 

2 

1 

L3 

1 

2 

2 

L2 

208 or 240V 

3Ø-Δ, 3W 

1 

3 

2 

L1 N L2 

Factory Default Setting 

2 

L3 

1 

1 

N 

1 

2 

L2 

480/277V 

3Ø-Y/4W 

50

Changing the V Grid Setting 

1 

2 

3 

4 

5 

6 

51

Local Monitoring- PVI-USB-RS485-232 

• Lowest cost monitoring - ~$100 

• Connects DIRECTLY to homeowner’s 

laptop or desktop via adapter 

• Free Aurora Communicator software 

• Rich data set: 

• Voltage/current for each MPPT block 

• Lifetime, Today, Last 7 days, Last 30 

Days, Last 365 Days 

• Grid voltage, current, frequency 

• Power transferred to the grid 

• Serial Number/Week Code 

• Firmware revision code

Local Monitoring- PVI DESKTOP 

• 3½” color touch screen display , table-top or wall 

mount 

• Inverter setup, diagnostics 

• Daily, Weekly, Monthly and Yearly energy 

production 

• 300 ft indoor, 900ft open field operating range 

• Communication with up to 6 string inverters 

• Can be wired or wireless Bluetooth 

53

Remote Residential Monitoring 

Aurora Vision 

30-days of local data buffering 

10 years monitoring included 

Applications requiring revenuegrade 

meter or weather stations 

need to use commercial kits 

Power Supply 

Eth 0 

Internet 

CAT5 Belden #3106A or equivalent 

Access to all recorded 

data is via web-based 

interface with enhanced 

productivity tools 

Inverter 

monitoring – 

up to 5 inverter 

54

Example 

Usage 

Define Daisy Chain 

+ 

- 

+ 

- 

+ 

- 

+ 

- 

+ 

- 

+ 

- 

+ - 

+ - 

+ - 

Series Parallel Daisy Chain 

Modules in a 

Strings in a 

Data 

string 

Combiner Communication 

55

Aurora PV Inverter Monitoring Wire 

RS-485 data connection 

The cable used must be shielded with 

twisted pair (MIN. #22AWG) 

impedance Z0=120Ohm. 

Shield must be continuous and 

terminated ONLY at ONE end point 

Signal Symbol Pair 

POSITIVE DATA +T/R A 

NEGATIVE DATA -T/R A 

GROUND 

REFERENCE 

RTN 

B 

• Connect RS-485 in a Daisy Chain configuration (“in-out”) 

• Set a different RS-485 address on each inverter for every 

inverter of the chain in the inverter configuration menu. 

• NO INVERTERS SHOULD HAVE “Auto” AS AN ADDRESS. 

• The communication length should be no longer than 1000m 

56

2 

Data Communications; Addressing the inverter 

4 5 

6 7 

1 

3 

When multiple inverters 

are connected in a 

daisy chain, it is 

necessary to assign a 

different RS-485 

address to each unit. 

Selecting the address 

menu enables the 

modbus addresses to 

be set to an appropriate 

value. Address values 

are assigned manually 

using any value in the 

range [2 to 64]. Press 

the UP and DOWN keys 

to scroll numbers. 

NOTE: Maximum 32 

inverters in a line. 

8 Etc. 

57

•Activate the termination resistor in the 

LAST inverter on the communication line by 

switching the dedicated dip-switch inside 

the inverter 

• Depending on the type of computer 

used, the cable line adaptor can be 

RS485-RS232 or RS485 to USB. 

58

Easy Installation 

Connect to internet 

(CAT5) 

Wire RS485 to inverter 

Belden #3106A or equivalent 

Connect and Plug into AC outlet

Easy Installation 


(CAT5) 

Connect to laptop 

for configuration 

(CAT5) 

Belden #3106A or equivalent 

Secondary RS485 is default set to 

Aurora Protocol 



Easy Installation (example) 

Secondary RS485 is default set to Aurora Protocol

Local Logger Configuration and set-up 


(CAT5) 

Connect to laptop 

for configuration 

(CAT5) 



Commissioning Process – Local Interface 

Put the following Aurora Logger Setup Tool into your internet browser bar: 172.17.17.1 

• Add device(s) and set Modbus address 

• Check device data 

• Confirm communication with Aurora 

Vision Server 

• Setup the meter, if included 

• Modbus address, CT Voltage, CT size, … 

• Setup Aurora Vision web interface 

• Plant properties, alarms, users, …

Possible Issues on Connection and Commissioning Logger 

Red Circle next to: 

• Credentials: call Power-One Tech Support to reset logger credentials 

• Server Login or Data transfer: Ensure the local internet security allows for data 

transfer, firewall protections, contact network administrator. Also consider using 

a static IP address 

64

Setting a Static IP Address: 

Most sites will not require 

this, usually more secured 

locations. 

Obtain Static IP address information for the site. 

• Select the Network tab. 

• Set the Type (Network Connection Type) field to 

Static. 

• The page will allow you to type in the following 

information: 

IP address 

Subnet Mask 

Gateway 

DNS 

• Press Update at the bottom of the page. 

65

Commission Data Logger 

Aurora Logger Setup Tool at 172.17.17.1 

If it does not detect inverters: 

• Wait a few minutes, “refresh” 

browser 

• Check individual inverter 

addresses inverter (ensure 

they are not the same) 

• Check termination resistor 

position 

• Check wiring connections 

Automatically detects 

P1 Inverters

Add Modbus RTU Devices 

Adding devices such as weather stations or non-P1 inverters 

• Select SunSpec Alliance Modbus Interchange as the Device Type from 

the pull-down menu. 

• Set the Slave Id field to the Modbus address of the weather station. Note 

that for the VSN-ENVIRO-ENTRY and VSN-ENVIRO-CMML weather 

station models the default Modbus address is 60. 

• Enter a Description to help you identify the device if you need to change 

configurations later.

Logger Registration to Aurora Vision 

IF Plant is already set-up on Aurora Vision website, then simply click on the 

Logger Registration tab to directly go to 

68

Aurora Vision Web Portal Overview 

1 

2 

Site 1 

1 

Login brings user to Portfolio page 

Summarizes aggregate plant information 

3 

2 

3 

4 

Assets 

Navigate and analyze devices and performance details 

Events 

Navigate and manage events for individual sites 

Reports 

Generates standard or custom reports for billing, operations and financial tracking 

4

Common Issues 

Locked Display 

A padlock symbol indicates that the display has 

been locked from scrolling. To enable scrolling, 

press the “enter” button. When scrolling is enabled, 

a double arrows symbol will appear. 

70

W003- Grid Fail or Grid out of range 

TL Models 

ISOLATED Models 

• Verify wiring 

• Use menu to select correct grid parameters 

Left selector Right 

selector 

Grid standard Display 

language 

0 0 Defa 

ult 

North 

America 

0 2 UL - 208 Single 

Phase 

North 

America 

0 3 UL - 240 Split Phase North 

America 

0 4 UL - 277 Single 

Phase 

North 

America 

• Completely power down unit, restart 

71

E013- Wrong Mode 

Dual MPPT DC Wiring Method 

• (Connection shown for product versions without integral DC switch) 

• Power down the inverter completely 

• Move switch back and forth several times 


• Verify NO Jumpers are installed 

72

E013- Wrong Mode 

Single MPPT DC Wiring Method 

• Power down the inverter completely 

• Verify switch S1 to PAR-parallel selection 

• Move switch back and forth several times 

• Jumpers are used in specified applications when strings are combined on 

the roof 

73

Ground Faults 

Using multi-meter: 

• Verify voltages to ground. 

• Ensure wires are removed from the 

inverter and checked in “open air” 

*take all necessary precautions as 

there will be voltages present on 

these wires 

• System w/ no leakage should start with 

indication of Voc/2, then voltage should 

bleed to/near 0. 

74

Indications of a ground fault 

If voltages do not drop to zero and 

stabilize at a certain value, then there 

is indication of a ground fault. 

These values can be used to 

determine approximate location. 

75

RISO Low 

Insulation Resistance can be affected by environmental conditions (wet, damp). 

Measurements should be taken immediately after the fault. 

76

Single Phase String Inverters: Summary 

Uno 

UNO-2.0-I 

UNO-2.5-I 

PVI 

PVI-3.8-I 

PVI-4.6-I 

PVI-3.0-TL 

PVI-3.6-TL 

PVI-4.2-TL 

PVI-5000-TL 

PVI-6000-TL 

Profitable 

• High CEC Efficiency 

• Fast & Precise MPP Tracking 

Algorithm 

Reliable 

• Natural Convection Cooling 

• NEMA 4X Enclosure Rating 

Flexible 

• Dual independent MPPT 

• Wide DC input voltage window 

Connected 

• Wireless monitoring solution 

77

Thank You! 

Technical Training 

Power 78 One of North America 

training@power-one.com

Single Phase String Inverters - Power-One

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