True Sine Wave Output

The INV-B inverter is controlled by a microprocessor to produce a true sine wave output with low harmonic distortion of <2% to <5% depending on the model. This is 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 standard IEC, Phoenix or Wago sockets depending on the model. Each inverter supplies 230V_AC output as standard, with 115V_AC options available for models up to 1kVA. Output frequency is adjustable between 50/60Hz via the front panel of 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.

Uninterrupted Power Supply (UPS) Functionality

The INV-B product family provides inverter capability with an AC input and integrated bypass, for continuity of supply during power failures. The inverter can be connected to external DC energy storage to run the load during grid outages. Alternatively, a secondary AC source can run the load when the DC supply is low or unavailable. Switching time is <10ms (typically <4ms).

On-line (DC Input Preferred)

When set to on-line, the INV-B will preferentially work in inverter mode. The DC input is treated as the primary supply, and the AC input will only be used when the DC supply is out of tolerance. See Safety and Protection for further details.

This mode is useful for installations with DC power generation, such as industrial DC grids, off-grid solar/wind power, or other battery storage systems with regular recharging. The AC supply can then take over running the load when the DC input is in need of recharging or maintenance.

Off-line (AC Input Preferred)

When set to off-line, the INV-B will preferentially work in bypass mode. The AC input is treated as the primary supply, and the DC input will only be used when the AC supply fails. See Safety and Protection for further details.

This mode is useful for systems with backup DC storage. A typical example is a UPS system where the AC load is run from batteries during grid outages or generator maintenance.

The inverter 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

The INV-B 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-B will shut down to prevent damage to the inverter. The system will automatically restart after a short period if the overload is corrected.

AC Overvoltage/Undervoltage

The voltage at the AC input is monitored, and the inverter will switch to the DC input supply if this is out of tolerance. If the DC supply is unavailable, the inverter will shut down. The overvoltage and undervoltage thresholds can be adjusted independently as required. When the AC supply is within tolerance again, the inverter will revert to the preferred input.

AC Frequency Monitoring

The frequency at the AC input is monitored, and the inverter will switch to the DC input supply if this exceeds the tolerance of ±3Hz. If the DC supply is unavailable, the inverter will shut down. When the AC supply is within tolerance again, the inverter will revert to the preferred input.

DC Overvoltage/Undervoltage

The inverter intelligently monitors the DC input voltage and switches to the AC supply if this fails. If neither the primary or secondary supplies are available, the inverter shuts down. 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. UVP: the undervoltage protection point causes automatic shutdown of the DC input during low voltage
3. Restart Low: after a low voltage shutdown, the DC input will restart when the voltage recovers
4. OVP: the overvoltage protection point causes automatic shutdown of the DC input during high voltage
5. Restart High: after a high voltage shutdown, the DC input will restart when the voltage recovers
6. Reset: if the DC supply is disconnected, the DC input will restart after returning to the First Start voltage

Reverse DC Connection

The DC input is protected against reverse connection¹, preventing damage in the event of reversed polarity of the DC source during initial connection.

^{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 according to CE and UKCA. The leakage current is <3.5mA.

The PE and neutral wires of the AC input are fed straight through to the inverter's output. This provides a consistent output potential when switching between AC and DC input modes.

Units in this inverter range are robust and extremely light, weighing between 7kg and 14kg. The wide operating temperature and excellent efficiency also help to ensure that the INV-B 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" rack mounting enclosures for easy installation. Each INV-B 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.

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.

If bypass functionality is not needed, INV-P inverters can be connected in parallel to combine outputs up to 20kVA. The inverters can be added, removed or exchanged without shutting down the system, allowing for true N+1 redundancy.