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PowerBack Temporary Power Restoration
At Bridgeport Magnetics Group, we help utility companies and linemen restore power faster with PowerBack temporary power restoration autotransformers. Our toroidal units deliver reliable balanced 120/240V or 120/208V service in minutes, combining superior portability, high-efficiency design, rugged construction, and uncompromising reliability for demanding field conditions.
Power Restored at the Meter in Minutes
PowerBack temporary power restoration autotransformers are wheeled service savers (also called add-a-phase, add-a-leg, phase restoration, or auto-cart units) that regenerate a missing hot leg or missing neutral on 120/240V or 120/208V single-phase service. Most models restore at the meter socket in minutes. The 50 kVA restores a multi-meter cabinet or pedestal on the incoming secondary. Designed by linemen, for linemen. Wound and assembled in Shelton, Connecticut. Typical lead time 1–2 weeks.
Every PowerBack uses a high-efficiency toroidal autotransformer, dual-trip protection (model-rated breaker plus a 105°C winding shunt trip), and a field connection built for a crew that has to leave the unit on-site. 15–30 kVA models use a single-turn meter adapter on ring-type and ringless bases (CL320 on the 30 kVA), plus a digital voltmeter. PowerBack Lite cuts weight to 91 lbs (15 kVA) and 110 lbs (20 kVA) on an aluminum/resin cart. Stainless 15–30 kVA units add a NEMA 4 enclosure. The 50 kVA lands with a Cam-Lok secondary kit when the outage is the whole bank, not one house.
Customers stay online. The dig becomes planned work. SAIDI stays intact.
Our Customers
PowerBack & Trident Models
Compare ratings, enclosures, and features across the lineup.
| Trident | Powerback-Lite 15KVA | Powerback-Lite 20KVA | Powerback 15kVA | Powerback 20kVA | Powerback 30kVA | Powerback 50kVA | |
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| High Efficiency Toroidal Auto Transformer | 20kVA (2x10kVA) | 15kVA | 20kVA | 15kVA | 20kVA | 30kVA | 50kVA |
| Recommended Service | 100A (oneAuto) 200A (twoAuto) | 150A | 200A | 150A | 200A | 320A | 400A |
| Circuit Breaker | 2x50A | 125A | 160A | 125A | 160A | 250A | 400A |
| (Dual Protections) Shunt Trip Temp. degC | NA | 105 | 105 | 105 | 105 | 105 | 105 |
| Corded Meter Adapter Included | 200A | 200A | 200A | 200A | 200A | 320A | No meter adapter - Cam-Lok kit, 10 ft 1/0 & 3/0 leads, 9-pc Flood-Seal/tinned whips. |
| Input/Output Voltmeters | Yes | Yes | Yes | Yes | Yes | Yes | NA |
| Integrated GFI with Defeat Switch | Optional | Optional | Optional | Optional | Optional | Optional | NA |
| GPS Tracking | Optional | Optional | Optional | Optional | Optional | Optional | Optional |
| Enclosure Type | Resin Case | Resin Case | Resin Case | NEMA 4 Stainless | NEMA 4 Stainless | NEMA 4 Stainless | NEMA 4 Stainless |
| Grounding | No Grounding Required | No Grounding Required | No Grounding Required | YES | YES | YES | YES |
| Dimensions (inches) | NA | 29 x 22 x 13 | 29 x 22 x 13 | 29 x 22 x 13 | 29 x 22 x 13 | 29 x 22 x 13 | 46 x 35 x 20 |
| Wheels (Diameter x Width) | NA | 10.5" x 3" | 10.5" x 3" | 10.5" x 3" | 10.5" x 3" | 10.5" x 3" | 12" x 4.5" |
| Weight (lbs.) | 45 / Auto | 91 | 110 | 120 | 140 | 220 | 290 |
The PowerBack was engineered with US Utilities - light & easy to maneuver, single-turn meter adapter, redundant overcurrent protection and built-in monitoring reliability - designed by lineman, for lineman
Light & Easy to Maneuver
A toroidal core makes Power-Back dramatically lighter than conventional E-I lamination units, so a single lineman can position it at the meter pan without a hoist or a second set of hands.
2x Trip Protection
Two independent trip paths: transformer
winding temperature and overcurrent. If either limit is reached,
PowerBack disconnects itself. Leave it on-site with confidence.
Never-flat Tires
Never-flat / airless tires for rough deployments –
driveways, gravel, mud, and storm debris.
Single-turn Meter Adapter
Connect at the meter in one turn. The Power-Back meter adapter installs fast and includes a neutral – so you restore service in minutes instead of running temporary above-ground conductors.
Made in USA: 1-2 wk leadtime
Every Power-Back is Manufactured in Shelton, Connecticut, with a 1–2 week lead time. No import delays.
When a Single Leg Fails, Don't Leave Customers in the Dark
An open hot leg or open neutral – storm damage, a failed underground cable, a burned connector – can drop a customer’s 120/240V or 120/208V service even when the transformer is fine. Finding and fixing that fault often takes days.
PowerBack service savers (also called add-a-phase, add-a-leg, or auto-cart units) put the missing conductor back online so the customer stays up. 15–30 kVA and Lite models connect at the meter with a single-turn adapter. The 50 kVA lands on the cabinet or pedestal secondary with a Cam-Lok kit. Two of the three service conductors still have to be good.
PowerBack restores the missing hot or the missing neutral – not both on the same service — and dual-trip protection watches the unit after the crew leaves. Schedule the permanent repair as planned work.
Back online in days, not weeks.
PowerBack and Trident temporary power restoration autotransformers – developed hand-in-hand with utility line crews, engineered and built in Shelton, Connecticut.
Frequently Asked Questions
What is PowerBack?
PowerBack is Bridgeport Magnetics’ wheeled line of temporary power restoration autotransformers – the units utilities call a service saver, add-a-phase, add-a-leg, phase restoration unit, or auto cart. High-efficiency toroidal models regenerate a missing hot leg or missing neutral on 120/240V or 120/208V single-phase service. Most restore at the meter in minutes. The 50 kVA restores a multi-meter cabinet or pedestal. Designed by linemen, for linemen in Shelton, Connecticut. Customers stay online while the underground repair is scheduled.
How does these units connect to the service?
15–30 kVA PowerBack and PowerBack Lite connect at the meter. Isolate the faulted conductor, remove the meter, land the single-turn adapter on a ring-type or ringless base (CL320 / HD 320A on the 30 kVA), set the meter back on, and energize. Neutral is in the adapter. No temporary overhead.
The 50 kVA does not use a meter adapter. It lands on the cabinet or pedestal secondary with a Cam-Lok kit: 10 ft 1/0 and 3/0 leads, then a 5 ft Flood-Seal or tinned whip.
What is the difference between PowerBack and Trident?
Same electrical job. PowerBack is the wheeled service saver: Lite at 91 lbs (15 kVA) and 110 lbs (20 kVA), stainless 15–30 kVA, and the 50 kVA multi-home cart. Trident is the 45 lb one-person carry-in service saver for stairs, alleys, gates, and yards a cart cannot reach. Both are designed by linemen, for linemen.
Can this Service Savor restore an open neutral as well as an open hot leg?
Yes. PowerBack Service Saver restores a missing hot or a missing neutral. Two of the three conductors still have to be good. It cannot restore a hot and the neutral at the same time on the same service. Size to the ticket: 15 kVA / 150A, 20 kVA / 200A, 30 kVA / 320A, 50 kVA / 400A multi-home.
What safety and monitoring features does PowerBack include?
Dual-trip protection is standard on every wheeled PowerBack — Lite, stainless 15–30 kVA, and 50 kVA. Two independent paths, one breaker.
Path 1 — overcurrent. A model-rated breaker opens on high current: short, bolted fault, or a sudden overload. That is the fast path. It does not see heat.
Path 2 – winding temperature. A 105°C sensor is mounted at the autotransformer winding, not on the cabinet wall. If the core and copper climb to 105°C while current is still under the breaker rating, the sensor shunt-trips that same breaker. That is the slow-heat path: load that sits for hours, blocked airflow, hot pavement, or solar export stacked on house load.
If either path fires, PowerBack disconnects itself. The crew can leave the cart on-site until the buried repair is scheduled.
What the crew sees
15–30 kVA models have a digital input/output voltmeter on the cart. Confirm 120V hot-to-neutral and 240V hot-to-hot before you leave. The 50 kVA is confirmed with a hand meter at a customer socket after the Cam-Lok landing.
Are these Service Savor units made in the USA and what is the lead time?
Yes – every PowerBack autotransformer is designed, wound, and assembled in our Shelton, Connecticut facility. Typical lead time is just 1–2 weeks with no import delays, giving utilities fast access to reliable domestic equipment.
What sizes and capacities are available in the PowerBack line?
The Wheeled Service Savor family includes models from 15 kVA (suitable for 150A services) up to 50 kVA (ideal for multi-home or larger commercial restorations). Popular options include the PowerBack Lite 15kVA and 20kVA for everyday residential use, plus higher-capacity wheeled units (20K, 30K, and 50K). This wide range allows utilities to match the right Service Savor solution to specific service requirements and site conditions.
How does PowerBack compare to traditional Servisavor or SNC Restore-Lite units?
They do the same job. A PowerBack, a Servisavor, and a Restore-Lite are all service savers: regenerate a missing hot or a missing neutral on single-phase 120/240V service so the customer stays up while the repair is scheduled. Capacities overlap — 15 kVA / 150A through 40–50 kVA multi-home.
The key difference is how the unit is built to support the lineman:
- Dual-trip protection. Every wheeled PowerBack has a model-rated breaker and a 105°C winding shunt trip. A breaker alone does not see slow heat from load, ambient, or solar export. Dual-trip does.
- Toroidal weight. The high-efficiency toroidal core is why Lite is 91 lbs (15 kVA) and 110 lbs (20 kVA), and why the stainless 15–20 kVA carts stay in the 120–130 lb range instead of a heavier E-I stack.
- Single-turn universal meter adapter. Ring-type and ringless on 15–20 kVA. CL320 / HD 320A on the 30 kVA. Neutral in the adapter. One turn, meter goes back on.
- Never-flat tires. Foam-filled, puncture-proof wheels for driveways, gravel, mud, and storm debris.
PowerBack is also wound and assembled in Shelton, Connecticut, with a 1–2 week lead time. The 50 kVA is the 400A-class cabinet unit – Cam-Lok secondary landing, 208A continuous per hot leg, no meter adapter. That is a different landing than a 40 kVA Restore-Lite on a 200A breaker.
Can PowerBack be used on a home with rooftop solar?
Yes, on 120/240V or 120/208V single-phase service, if two conductors are still good and the install follows your utility’s procedure.
A service saver does not block reverse power. After the missing hot or missing neutral is restored, the meter looks normal. The inverter may stay online or reconnect after its delay. Export current then runs through PowerBack and adds heat in the windings on top of house load.
Field rule:
- Isolate or disconnect the solar equipment if your procedure requires it. That is the cleanest install.
- If the array stays connected, treat export as added load. Do not put a 15 kVA unit on a 200A house that is also exporting.
- Confirm 120V hot-to-neutral, 240V hot-to-hot, and a believable current reading before you leave.
- Do not assume the inverter is off just because one utility conductor is open.
- If PowerBack trips, do not reset and walk away. Check whether the array is exporting, then confirm the unit still matches combined load.
Dual-trip is the layer that opens on slow heat if export plus house load climbs while the cart sits. Optional GFI is a separate ground-fault / imbalance layer. Neither replaces disconnecting the array when your procedure calls for it.
When should we spec the GFI option?
Optional GFI is a third protection layer on PowerBack. Dual-trip already covers overcurrent and winding heat. GFI covers a ground-fault / imbalance condition dual-trip does not see.
A current sensor inside the enclosure watches all three conductors against neutral balance. If the restored service develops an 8 amp imbalance, GFI trips the main breaker. That is the published trip — neutral-failure / leakage protection, not a 105°C heat trip.
GFI is wired to a defeat toggle. Leave it off while you land the adapter and restore the missing hot or missing neutral. Confirm 120V hot-to-neutral and 240V hot-to-hot first. Then enable GFI. Turn it on too early and it can nuisance-trip before the customer is back.
The brochure install for this option includes a driven ground rod to the chassis. Follow that when the GFI package is on the cart.
Use GFI when
- Wet yard, snow, flood, irrigation
- Occupied house – kids, pets, outdoor equipment
- Unit will sit for days
- Multi-home pedestal or multi-meter cabinet
- Insulation is questionable
Do not treat GFI as
- A substitute for dual-trip
- Protection against solar export (export is heat and sizing)
- A reason to skip isolating the faulted conductor
Restore first. Prove voltage. Then close the GFI toggle and leave the unit on-site.
