Unit 5
An autotransformer uses the same winding as the primary transformer, but doesn't bit use the same winding as the secondary transformer.
False
Autotransformers rarely have multiple taps to provide different voltages.
False
If the number of primary turns is the sum of the turns between taps (such as 80 + 100 + 60 = 240 turns), and 120 volts are connected across the 240 turns, this transformer will have a volts-per-turn ration of 2.0
False
If the primary section of a transformer is connected across part of a winding, and the secondary is connected across the entire winding, the secondary section contains more windings than the primary. This is a step down transformer.
False
The amount of current flow in a secondary circuit can be computed using the formula I = Z/E
False
The primary current can be computed by using the same formula that is used to compute primary current for an isolation-type transformer.
False
An autotransformer is literally a self transformer
True
Autotransformers, like isolation transformers, can be used as a step up or step down transformer.
True
The amount of power input and output for an autotransformer must be the same.
True
The autotransformer's one disadvantage can cause problems with certain types of equipment and must be s consideration when designing a power system.
True
Autotransformers have high efficiencies, most in the range of what percent?
95-98%
Current for primary can be computed by what formula?
Ep/Es = Is/Ip
If the amount of voltage applied to the load is to be computed, which formula can be used?
Ep/Es = Np/Ns
To calculate the current flow supplied to the primary, use the formula Ip =
Is/Ratio
The autotransformer has one disadvantage: Since the load is connected to one side of the power line, there is no what between the incoming power and the load?
No line isolation
The volts-per-then for any transformer is determined by the what?
Primary winding
If a rotary switch were to be removed and replaced with a sliding tap that made contact directly with the transformer winding, the turns ratio could be adjusted continuously. This type of transformer is commonly referred to as a what? Depending on the manufacturer
Variac or Powerstat