TX91L Isolation Online UPS – Extended Runtime Power Quality UPS (3.8–10kVA, 120/240V)
3.8–10 kVA | 240/120V or 230/115V | Online Double-Conversion UPS with Isolation Transformer
Isolation-based online UPS engineered for electrically challenging environments requiring both superior power quality and extended runtime.
3.8–10 kVA · 240/120 VAC (or 230/115V) · Isolation Online UPS · External Battery · Extended Runtime · TAA
TX91L extended-runtime isolation online UPS
The TX91L is an isolation-based online double-conversion tower UPS (3.8 to 10 kVA) built for environments where both electrical noise and outage duration are critical design factors. Unlike internally battery-integrated platforms, the TX91L is engineered around scalable external battery systems — so runtime can be sized from minutes to multiple hours to match the site. An integrated galvanic isolation transformer electrically separates the utility input from the load, eliminating common-mode noise that transformerless designs leave exposed, while a programmable 1–4 A charger supports the large battery strings that extended runtime requires. True sine wave output, ±1% regulation, ANSI/IEEE C62.41 surge protection, dual output voltages, generator compatibility, a 3-year electronics warranty, and TAA compliance.
Power quality and extended runtime in one isolation platform
The TX91L defines the category of isolation-based UPS systems optimized for extended-runtime deployment. It is built for facilities that must address two problems at once: electrical instability — noise, grounding issues, harmonic distortion, transients — and outage duration. The integrated isolation transformer conditions power at the source, while a scalable external battery architecture engineers runtime to the application, from ride-through and generator stabilization to multi-hour facility continuity. Standard online UPS platforms provide continuous conditioning but do not address electrical noise and extended runtime to the same degree within a single unit.
Runtime engineered to the site, not fixed to the chassis
The TX91L carries no internal batteries. Runtime is delivered entirely by external battery systems sized to the deployment, which is what lets a single platform span short ride-through and multi-hour continuity. A programmable 1–4 A charger (273 VDC, set from the LCD) is sized to recharge the larger battery strings that long-duration runtime depends on.
| Runtime objective | How the TX91L supports it |
|---|---|
| Ride-through & controlled shutdown | Smaller external strings cover brief outages and orderly shutdown of sensitive systems |
| Generator startup & stabilization | Bridges and stabilizes the load while generator-backed infrastructure starts and settles |
| Multi-hour facility continuity | Large external battery systems extend runtime to hours for prolonged-outage strategies |
| Site-specific sizing | Battery capacity is matched to load and continuity targets rather than a fixed internal pack |
Because runtime is defined by external battery configuration, it is engineered per site. Contact Xtreme Power at (800) 582-4524 or sales@xpcc.com for runtime sizing, or use the UPS sizing tool.
Integrated galvanic isolation, standard on every model
The isolation transformer is integrated as standard on every TX91L, not specified as an option. Unlike transformerless UPS platforms, the TX91L uses that transformer that electrically separates the utility input from connected loads — and provides power conditioning during both normal and bypass operation. This architecture mitigates the disturbances that degrade reliability in electrically challenging environments, including the one no other UPS topology addresses:
| Disturbance | How isolation addresses it |
|---|---|
| Common-mode electrical noise | Galvanic separation breaks the common-mode path between source and load |
| Harmonic propagation | Isolation limits harmonic coupling from shared loads on the same supply |
| Ground reference instability | A stabilized ground reference supports sensitive equipment |
| Voltage transient propagation | Transients are attenuated rather than passed through to the load |
The result is improved waveform integrity and a stable ground reference — without the expensive dedicated circuits a non-isolated approach would require.
What the TX91L delivers
No internal batteries — runtime is delivered by external battery systems sized to the site, enabling everything from ride-through and generator stabilization to multi-hour facility continuity within one platform.
A high-current charger, adjustable from 1 to 4 A at the LCD (273 VDC), is sized to recharge the large external battery strings that extended runtime requires.
Eliminates common-mode noise left exposed by transformerless online designs, removes the need for expensive dedicated circuits, and provides power conditioning during both normal and bypass operation.
High-quality true sine wave output with tight ±1% regulation and dual output voltages (240/120V or 230/115V), plus an optional configurable PDU for a wide range of receptacle requirements.
Surge withstand to Category A & B (6kV / 200 & 500A, 100kHz ringwave) with very low let-through — under 10V normal mode (L-N) and under 0.5V common mode (N-G) at 6kV Cat A.
A static switch transfers output to the isolated bypass source on overload or fault, a manual maintenance bypass enables service, and auto restart plus generator compatibility suit generator-backed infrastructure.
Same isolation, different runtime strategy
The TX91L and TX91 share the same isolation architecture but are optimized for different deployment strategies. Choose the TX91L when runtime requirements exceed internal-battery capabilities, or when large battery systems are needed for facility-level continuity planning. Choose the internal-battery TX91 for compact, self-contained, laboratory-focused power quality.
| Attribute | TX91L (this platform) | TX91 (internal battery) |
|---|---|---|
| Battery architecture | External battery systems (no internal batteries) | Internal batteries (external packs optional) |
| Runtime profile | Extended — minutes to multiple hours, site-engineered | Short-duration ride-through and shutdown |
| Charger | Programmable 1–4 A for large strings | Standard charger for internal packs |
| Primary use | Infrastructure continuity & generator-backed sites | Laboratory / analytical power quality |
| Isolation transformer | Integrated | Optional, integrated |
The extended-runtime isolation tier of the Xtreme Power family
The TX91L sits where electrical isolation and outage duration are both primary design requirements. It complements the runtime-flexible P91 rack platform and the internal-battery TX91, and pairs with lithium platforms for higher-density facility continuity.
Where conventional online UPS runs out of runtime
Standard online UPS systems provide continuous power conditioning but do not address electrical noise or extended runtime at the same level. Transformerless platforms prioritize efficiency and compact size while providing no electrical isolation between input and output. The TX91L extends beyond conventional UPS functionality by combining isolation-based power conditioning with scalable external battery systems — suited to environments where electrical instability and outage duration both impact performance.
| Capability | TX91L (isolation + external battery) | Conventional / transformerless online |
|---|---|---|
| Electrical isolation | Integrated galvanic isolation transformer | None (input and output share reference) |
| Common-mode noise | Eliminated at the transformer | Passed through to the load |
| Runtime ceiling | Scalable external battery — up to multiple hours | Bounded by internal / fixed battery |
| Primary design goal | Power quality + extended continuity | IT load protection / efficiency |
Four models, 3.8–10 kVA, external battery only
| Model | Capacity (kVA / kW) | Dimensions (W × D × H) | Weight |
|---|---|---|---|
| TX91L-3.8K | 3.8 / 3.8 | 9.9 × 23.3 × 22.7 in | 152 lb |
| TX91L-5K | 5 / 5 | 9.9 × 23.3 × 22.7 in | 155 lb |
| TX91L-6K | 6 / 6 | 9.9 × 23.3 × 22.7 in | 158 lb |
| TX91L-10K | 10 / 10 | 9.9 × 23.3 × 32.4 in | 187 lb |
All models are tower form factor with unity output power factor, ±1% regulation, an integrated isolation transformer, and a 273 VDC programmable charger (1–4 A, set at the LCD). Batteries are external. Input and output land on terminal blocks or an optional configurable PDU; an input L6-30P cord is available on the 3.8 / 5 / 6 kVA models (6 kVA capacity is reduced by a 30 A input circuit), while the 10 kVA lands on terminal blocks.
Where the TX91L is deployed
The TX91L is deployed where both electrical conditions and outage duration require engineered solutions — industrial automation systems, retail and distributed commercial infrastructure, laboratory and analytical environments, medical diagnostic systems, broadcast and AV infrastructure, and facilities with unstable utility or generator-backed power. It is commonly chosen to replace conventional UPS systems that lack sufficient isolation or runtime, and to standardize both isolation and runtime strategy across distributed or facility-level deployments.
TAA compliance for regulated continuity programs
The TX91L supports regulated commercial, government, and industrial deployments requiring Trade Agreements Act compliance, alongside UL1778, cUL, FCC Class A, and RoHS.
TX91L specifications
| Models | TX91L-3.8K / -5K / -6K / -10K (3.8 / 5 / 6 / 10 kVA = kW) — unity PF |
| Topology | Online double-conversion, single-phase; integrated galvanic isolation transformer |
| Battery | External battery architecture (no internal batteries); runtime sized by external battery configuration |
| Charger | 273 VDC; programmable 1–4 A (max), set at the LCD — sized for large external battery strings |
| Input | 208 VAC nominal (220 / 230 / 240 VAC optional); range 110–300 VAC; 46–64 Hz auto-sensing; terminal blocks or optional PDU |
| Output | 240/120 VAC or 230/115 VAC; ±1% regulation; 50/60 Hz ±0.1 Hz; true sine wave |
| Efficiency | Up to 97% ECO mode, 91% online mode |
| Overload | 200% / 150% / 130% for 1 min (model-dependent — see datasheet) |
| Surge let-through | <10V normal mode (L-N), <0.5V common mode (N-G) at 6kV ANSI/IEEE C62.41 Cat. A |
| Surge withstand | ANSI/IEEE C62.41 Category A & B; 6kV / 200 & 500A, 100kHz ringwave |
| Bypass / transfer | Static switch to isolated bypass on overload or fault; manual maintenance bypass; auto restart; generator compatible |
| Dimensions / weight | 9.9 × 23.3 × 22.7 in (3.8 / 5 / 6 kVA), 9.9 × 23.3 × 32.4 in (10 kVA); 152 / 155 / 158 / 187 lb |
| Connections / PDU | Terminal blocks or optional PDU; 120V receptacles 5-15/20R; 240V receptacles L6-30R, L6-20R, 6-15/20R, C19; optional input L6-30P cord (3.8 / 5 / 6 kVA) |
| Communications | RS-232, EPO, USB; intelligent slot (Web/SNMP, Relay/dry contact, Modbus); ViewPower software |
| Environment | 32–104°F (0–40°C); audible noise <50 dBA; altitude 11,500 ft |
| Approvals | UL1778, cUL, FCC Class A, RoHS, TAA compliant |
| Warranty | 3 years electronics (USA and Canada); 5-year extended available |
| Options | Output PDU, input L6-30P cord (3.8 / 5 / 6 kVA), external battery systems, 5-year extended warranty |
TX91L extended-runtime isolation UPS — frequently asked questions
Why does the TX91L have no internal batteries?
Because a fixed internal pack caps runtime at whatever fits in the chassis. Moving the entire battery system external lets one platform span short ride-through through multi-hour facility continuity, sized to the site rather than to the enclosure. It also means battery capacity can grow later without replacing the UPS.
How much runtime can the TX91L deliver?
There is no fixed answer, which is the point. Runtime is a function of the external battery configuration and the load, and ranges from minutes for ride-through and controlled shutdown up to multiple hours for facility continuity. A programmable 1-4 A charger at 273 VDC, set from the LCD, sizes recharge to the string. Contact Xtreme Power at (800) 582-4524 for runtime sizing.
What is the difference between the TX91L and the TX91?
Both share the same isolation architecture. The TX91 carries internal batteries with optional XR packs and external BP960 cabinets, and targets compact, self-contained laboratory power quality. The TX91L carries no internal batteries and is engineered around scalable external battery systems for infrastructure continuity and generator-backed sites. Isolation is integrated as standard on the TX91L and an integrated option on the TX91.
How long does it take to recharge the external battery strings?
That depends on string size, but the charger is the constraint worth planning around. The TX91L uses a programmable 1-4 A charger at 273 VDC, adjustable at the LCD, specifically because large external strings need more charge current than a standard internal-pack charger provides. Size the charger setting to the string when you specify the battery system, not afterward.
Can the TX91L bridge a generator start?
Yes, and it is one of the primary use cases. Online double-conversion regenerates output frequency, so the TX91L accepts generator power instead of rejecting it as out of tolerance. External battery capacity covers the interval while generator-backed infrastructure starts and settles, and auto restart plus static bypass to the isolated bypass source support that sequence.
Does the TX91L include the isolation transformer as standard?
Yes. The galvanic isolation transformer is integrated on every TX91L model rather than specified as an option, which is a difference from the TX91. It conditions power during both normal and bypass operation.
What does the isolation transformer actually protect against?
Common mode noise, measured between ground and either neutral or line. It is the tenth of the ten common power problems and the only one online double-conversion alone does not address. Galvanic separation breaks the common mode path between source and load, limits harmonic coupling from shared supplies, and stabilizes the ground reference. Note that the load should connect directly to the UPS output; feeding it through a downstream PDU or power strip reintroduces the ground paths the transformer was installed to break.
Is the TX91L TAA compliant?
Yes. The TX91L is TAA compliant and carries UL1778, cUL, FCC Class A, and RoHS, supporting regulated commercial, government, and industrial procurement.
Documents and related links
Plan your TX91L deployment
Talk to an Xtreme Power specialist about isolation requirements, external battery sizing for minutes-to-hours runtime, generator coordination, PDU and receptacle configuration, and TAA-compliant deployment for industrial, laboratory, medical, broadcast, and facility-continuity environments.