Takes AC signal and passes both positive and negative voltage alternations so that pulses through load are same polarity.

Essentially takes AC voltage and turns it into DC voltage.

Describe the function of an isolated bus

A heavy, hollow (copper or aluminum) bus enclosed in a sheet metal pipe used to conduct large power output current of main generator to its main transformer.  Called main bus duct.  Conductor supported inside pipe by heavy insulators.  

Explain reasons an isolated phase bus requires a cooling system

Cooling air is forced through ducts to remove heat.

Carries and distributes most electricity inside the plant.  Copper or aluminum bars are rigidly supported by insulators inside a metal housing.

Metal housings that contain electrical buses and circuit breakers.

In switchyards or substations, buses are open to the air.  Buses are placed high above the ground and supported by porcelain insulators.

Describe the advantages and disadvantages of:

Transfer bus

Transfer-bus sometimes added to supply loads during main bus outage.

Adv- Very reliable

Dis- Cost is more then radial or ring bus

Describe the advantages and disadvantages of:

Parallel bus

Parallel-bus capable of handling full-load capacity sometimes replaces a T-bus. (If either system fails, no interruption in power occurs)

Adv-  highly reliable but circuit breakers are expensive.

Dis- More expensive then Transfer bus

Describe the advantages and disadvantages of:

Radial bus

Simplest arrangement, single main bus. Used for nonessential loads.

Adv- least expensive

Dis-Least reliable

Describe the advantages and disadvantages of:

Ring bus

Adv-  has the reliability of the parallel bus and the economy of the radial bus.

- No circuit breakers to disconnect each line.

- Each line attached directly to ring bus.

- Divided into sections by ring bus circuit breakers.

Once opened, it behaves like a radial bus.