Parallel Outputs

Up to 5 INV-P modules can be connected in parallel to make a single, synchronised output. The load is automatically shared between all parallel modules, and dynamically adapts as modules are added, removed, or swapped. Each module is also able to operate independently, so that systems can be reconfigured, expanded, or broken up as needs dictate.

The modular approach is useful for installations that might need to power many different sized power devices. Individual modules can be used for the day-to-day running of multiple small devices, then grouped together for larger projects. If power use increases after commissioning, then the system can be easily expanded to match the new requirement. The example below shows parallel connection of 5× 4kVA models.

^{1 This is the maximum continuous apparent power at max PF. See the Safety and Protection section for output overload information.}

N+1 Redundancy

Units can be added or swapped without powering down the system. True N+1 redundancy can therefore be achieved by including redundant units that can be exchanged as required, with no interruption to the output. By using a system with additional redundant inverters in parallel, the remaining inverters will smoothly take over the load sharing in the event of failure or disconnection of any unit.

True Sine Wave Output

The INV-P inverter is controlled by a microprocessor to produce a true sine wave output with low harmonic distortion of <3%. This is well within the UK grid tolerance of <5%, and significantly better than square, modified sine or quasi-sine wave inverters which produce very high levels of distortion. A pure sine output ensures that even sensitive electrical devices, such as computerised loads, can run smoothly from the inverter.

The AC output is provided via Phoenix-style connectors, with additional standard IEC sockets for models up to 2kVA. Each inverter supplies 230V_AC output as standard, with 115V_AC options available for models up to 2kVA. Output frequency of 50/60Hz is adjustable on the unit.

Wide DC Input Range

A large selection of nominal DC input voltages are available. Each unit has a wide input range for compatibility with the highly variable voltages of many DC power storage systems, such as batteries or capacitors. The inverter can continue to run without interruption even during large fluctuations of the input voltage. Voltage limit parameters can be adjusted as required within the range for most models, see Safety and Protection for further details.

A variety of DC Inputs are available, please see the selection table for more information.

The modules can be set up entirely from the front panel, including changing the output frequency between 50Hz and 60Hz. For certain models, more settings are available via the built-in LCD display such as overvoltage and undervoltage thresholds. 2kVA and 4kVA models can include an optional LAN interface to allow monitoring through a web browser, or through an NMS (Network Management System) via SNMP (Simple Network Management Protocol).

Output Overload/Short-Circuit

Each INV-P inverter can provide an output in excess of its nominal ratings for short periods. This is ideal for applications with surges in power demand, such as a motor’s start-up current.

If the overload capacity is exceeded (e.g. due to a short-circuit) then the INV-P will shut down to prevent damage to the inverter. The system will automatically restart after a short period if the overload is corrected.

DC Overvoltage/Undervoltage

The inverter intelligently monitors the DC input voltage and shuts down if this breaches the expected limits. The system will automatically reconnect when the input voltage returns to normal levels, with built-in hysteresis of the reconnection. This ensures a stable input is available prior to switching the output on.

For models with LCD display or LAN connectivity, all parameters below can be adjusted as required within the input range of the inverter. The system can be optimised for different DC supplies by adjusting the input voltage parameters, such changing the UVP as to avoid over discharge of different battery chemistries.

1. First Start: the voltage required to start the inverter on initial connection.
2. Shut Down UVP: the undervoltage protection point causes automatic shutdown due to low input voltage.
3. Restart Low: after a low voltage shutdown, the inverter will restart when the voltage recovers.
4. OVP: the overvoltage protection point causes automatic shutdown due to high input voltage.
5. Restart High: after a high voltage shutdown, the inverter will restart when the voltage recovers.
6. Reset: if the DC supply is disconnected, the inverter will restart after returning to the First Start voltage.

Reverse DC Connection

The DC input is protected against reverse connection¹. This prevents damage in the event of reversed polarity of the DC source limit during initial connection, up to the input voltage.

_{1 Excluding 4000VA/48V models}

Overtemperature

Each inverter uses temperature and load-controlled fans to cool the module. This allows operation at full power across a wide temperature range of -5°C to +45°C/+50°C, depending on the model. Above the temperature range maximum, the output of 2kVA and 4kVA models is automatically derated for protection and continuous operation up to +70°C.

The AC output is galvanically isolated from the DC input at 3.75kV_DC. The case of the inverter is electrically isolated, with a standard Y-capacitor connection between AC and ground. This is required to meet EMC requirements of CE and UKCA. The leakage current is <3.5mA.

Units in this inverter range are robust and extremely light, weighing between 7kg and 11kg. The wide operating temperature and excellent efficiency also help to ensure that the INV-P is ideal in numerous applications. Further ruggedisation is optionally available, increasing resilience against shock, vibration, and condensing humidity. This is useful for units installed in motor vehicles, boats, or any other system that might experience movement, vibration, or an uncontrolled environment.

All units are compatible with standard 19” rackmounting enclosures for easy installation. This is useful for parallel systems, where multiple units can be installed in one rack. Each INV-P is 3U high with a depth of 240mm/360mm depending on the model. Connectors are built on the front of the inverter as standard. If required, input and output connectors can be installed on the rear panel at no additional cost.

The INV-B product family provides DC-AC inverter capability up to 4kVA. These units include an AC input and bypass in addition to the DC input. This provides continuity of supply during power failures. DC energy storage can run the load during grid outages, or a secondary AC source can run the load when the DC supply is low or unavailable. The primary/secondary source is settable by the user.

For higher power applications, the INV-LAVA-4000 product family can include an optional bypass with hot-swappable units for N+1 redundancy. This is ideal for critical applications such as telecommunications or power station control systems. The installation can also be expanded with additional units, providing an output up to 48kVA.

A ruggedised version of the INV-P was supplied to the North Norfolk Railway for a vintage diesel locomotive. The train had a discontinued boiler on-board which required a 230Vac input, whilst only having 110Vdc power available from an auxiliary generator, needing a reliable DC-AC inverter for the conversion.