new used transformersESU, Inc. has a large inventory of new and used buck boost and auto transformers  If you require I phase 3 Phase 208/240, 208 to 240, 208 to 480, 120 to 240 or other voltages we usually have the transformer in stock.

We usually stock Acme, Westinghouse, Cutler Hammer, ITE Siemens, FPE  Federal Pacific, Square D, General Electric and Zinsco products.

We also carry a wide variety of commercial power transformers. Low Voltage Distribution General Purpose Commercial Transformers for all of San Diego. ESU offers a wide selection of electrical products that include buck-boost transformers, low voltage lighting transformers, mini power centers, and autotransformers.

All our recycled equipment has been tested and has our guarantee.

An electrical transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called mutual induction


A single phase transformer is a type of transformer which operates on single-phase power. 

Single-phase transformers are usually used for single special applications or voltages. For instance, equipment that specifically requires 240 volts single-phase where the service voltage is 120/208 volts. For an application like this, it is common to only provide a single-phase transformer for the equipment because there won’t be a different electrical loads served by it. 

Phase imbalances can occur when a single-phase transformer is used for general distribution while using a three-phase utility. If a property is served by single-phase and a transformer is used (e.g., for isolation) then a single-phase transformer would be appropriate.

Three-phase transformers are a type of transformers that are used to change voltages of electrical systems with three phases. There are different types of configurations for three phase transformers: star-star, delta-delta, star-delta, and delta-star. 

Core-type transformers act as a single-core, three-phase transformers where each phase is magnetically coupled to each other.

We have a large inventory of most brands of circuit breakers. We carry a large variety of manufacturers, including Zinsco, Federal Pacific FPE, Pushmatic, Bulldog, Cutler, Hammer, ITE Siemens, Square D etc. in our San Diego store.  We are circuit breakers and electrical hardware experts. Do not hesitate to call us at 858.558.2850 to find out which Circuit Breaker is right for your requirement.

used circuit breakerElectrical Supplies Unlimited is your company's business source for testing, repairing, rebuilding or reconditioning electrical equipment. ESU maintains a wide variety of out of stock circuit breakers, relays, transformers, switches, relays, motor controls, and other electrical equipment. ESU will also purchase your excess electrical inventory. We also buy new and used transformers. Call us today to find out more! Some merchandise may be available as used or surplus, just call one of our representatives to find out more!

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.

Our large selection of fuses up to 3000 amp will usually satisfy most requirements for your job. We carry many brands including Buss and Little Fuse among others. Call today and get your fuse requirements fulfilled at Electrical Supplies Unlimited

An electrical fuse is a current interrupting device which protects an electrical circuit in which it is installed by creating an open circuit condition in response to excessive current.

When the element in a fuse receives too much heat it will melt and interrupt the current. Fuses are usually used as a conduit between an electrical power source and an electrical component or a combination of components arranged in an electrical circuit. A fusible link is connected between the fuse terminals. This means that when an electrical current passing through the fuse goes beyond what the device is able to handle, the fusible link will melt and the circuit opens thus preventing electrical component damage.

Fuses are typically made for single time use. In other words, once it shuts a device down it must be replaced. You can get over-current protection from a variety of sources such as circuit breakers, switches, and relays. Each type of equipment has variations in ratings, service requirements and costs. Fuses are typically the most economical means for providing automatic high-voltage current protection against a single over-current failure.  Contact Electrical Supplies Unlimited for your electrical fuse supply needs.

commercial service electrical equipment

We can supply most major commercial services from 100a  and up. We are experts in multi-units add-ons and can modify or certify equipment to underwriters laboratory UL specifications through our network of service providers.  Amongst the products we stock or have access to are Siemans ITE, Cutler Hammer, Federal Pacific, GE, Square D, Challenger and others.

We have a large inventory of Safety Switches up to 400 amps 600v in stock both new and used to satisfy your electrical needs. We stock most makes. From  15 amp to 600 amp   240v to 480v single phase and three phase indoor Nema 1  and outdoor Nema 3.

We can supply most makes of panelboard switches and mounting hardware. These include Zinsco, Bulldog, Pushmatic, Square D, Challenger  and ITE Siemans among others.

A panelboard (or distribution board) is a component of an electricity supply system which divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit, in a common enclosure. Normally, a main switch, and in recent boards, one or more Residual-current devices (RCD) or Residual Current Breakers with Overcurrent protection (RCBO), will also be incorporated.