Isolation transformers for sale, 3 phase 480 V

True isolation or a standard delta wye

Every two winding transformer isolates, because nothing connects the primary to the secondary except the magnetic core. A standard 480 delta to 208Y/120 building transformer is already an isolation transformer in that sense. What buyers usually mean by an isolation transformer is a unit at the same voltage in and out, most often 480 delta to 480Y/277, bought for one of three reasons.

Maddox explains the main one. An isolation transformer keeps ground currents induced on the load side from circulating back to the building source, and creates a separately derived system for the load. The second is a neutral, since a 480Y/277 secondary can feed 277 V lighting where the plant has only three wire 480. The third is noise, where an electrostatic shield is added.

Configurations we quote at 480 V

Send the primary and secondary voltage and whether you need a neutral. If the secondary must be a grounded wye, say so.

• 480 delta to 480Y/277, the classic isolation unit, also sold as a drive isolation transformer
• 480 delta to 208Y/120, the building step down, isolating by design
• 480 delta to 240 delta or 240 delta with 120 V center tap, for older 240 V equipment
• 208 delta to 480Y/277 step up, for 460 V motors and machines on a 208 V service
• 600 delta to 480Y/277 or 208Y/120 for Canadian systems

Amps by kVA

Full load current for three phase isolation transformers at the common voltages, computed from kVA times 1000 divided by the voltage times 1.732.

Computed. For a 480 to 480 unit both windings carry the 480 V current.

Public prices, November 2026

Asking prices from distributor and maker listings read in November 2026, not our prices. Branded US units at 480 delta to 480Y/277 cluster around $6,500 to $7,800 at 75 kVA. ATO, which sells direct, lists odd export voltages such as 480 to 400 and 480 to 220 that suit imported machines.

Asking prices from the sources listed below. Freight and taxes extra unless stated.

Lead times

Phoenix Phase Converters ships its stock 480 delta to 480Y/277 units, 15 to 500 kVA, in 3 to 5 business days. HomElectrical lists the Hammond 75 kVA drive isolation unit as made to order, shipping in 30 to 45 days. Canada Transformers lists 2 to 3 weeks to build its small single phase units. A large or special unit goes on the dry type factory schedule, which Terrapin Construction Group put at 20 to 32 weeks in 2026 for units up to 2 MVA.

Shielded, K rated and drive isolation

An electrostatic shield is a grounded copper foil between the windings. Hammond Power Solutions says it shunts some noise and transients to ground instead of passing them to the secondary, and that K rated transformers must have one. Hammond also notes that recent testing has questioned how much a shield helps when the secondary is grounded, which covers most installations.

A K rated unit is built for harmonic heating from electronic loads. Maddox says K rated units have 200 percent rated neutrals and a shield as standard.

A drive isolation transformer feeds a variable frequency drive. Maddox says these are rated for 150 percent overload for 60 seconds and 200 percent for 30 seconds, come with 100 percent rated neutrals, make the shield optional, and are sized to motor horsepower, so 7.5 hp takes 11 kVA and 50 hp takes 63 kVA. A standard isolation unit on a drive can overheat, while a drive isolation unit can serve as a standard one.

How much does a 3 phase isolation transformer cost

In November 2026 public listings put a 75 kVA, 480 delta to 480Y/277 unit at about $6,500 to $7,800 from Acme, Hammond and Phoenix Phase Converters. ATO listed 30 kVA at $5,129 and 300 kVA at $30,086 at export voltages.

What is a 480 delta to 480Y/277 transformer for

It gives a three wire 480 V system a grounded wye with a neutral, creates a separately derived system for the load and keeps ground currents from a drive or machine on the load side.

Is a delta wye transformer an isolation transformer

Yes. Any two winding transformer isolates its secondary from its primary. The name isolation transformer is usually used for units with the same voltage in and out.

What is the difference between a drive isolation and a K rated transformer

Maddox says a drive isolation unit has a 100 percent neutral, an optional shield and overload capacity for motor starts, while a K rated unit has a 200 percent neutral and a shield as standard for harmonic heating.

What size isolation transformer for a 50 hp drive

Maddox sizes drive isolation units to horsepower and lists 63 kVA for 50 hp.

How fast can I get an isolation transformer

Stock 480 delta to 480Y/277 units ship in 3 to 5 business days from sellers such as Phoenix Phase Converters. Made to order units run 30 to 45 days or more.