adapt ,
application
fraction
volt-ampere -
power supply
impedance matching
circuit (),
circuit isolation ()
range
power frequency
audio frequency
ratio frequency
cooling
distribution
rectifier
arc furnace
amplifier output
step-up transformer
step-down transformer
isolating transformer
coil , ,
equal ,
compensate
variable transformer .
III. Read and translate the text.
The equation shows that the EMF of a transformer at a given flux density increases with frequency. By operating at higher frequencies, transformers can be physically more compact without reaching saturation, and a given core is able to transfer more power. However, other properties of the transformer, such as losses within the core and skin-effect, also increase with frequency. Generally, operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetising (no load primary) current. At a frequency lower than the design value, with the rated voltage applied, the magnetising current may increase to an excessive level.
Operation of a power transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. For example, transformers at hydroelectric generating stations may be equipped with over-excitation protection, so-called "volts per hertz" protection relays, to protect the transformer from overvoltage at higher-than-rated frequency which may occur if a generator loses its connected load.
Classifications. Transformers are adapted to numerous engineering applications and may be classified in many ways:
- By power level (from fraction of a volt-ampere(VA) to over a thousand MVA),
- By application (power supply, impedance matching, circuit isolation),
- By frequency range (power, audio, radio frequency(RF))
- By voltage class (a few volts to about 750 kilovolts)
- By cooling type (air cooled, oil filled, fan cooled, water cooled, etc.)
- By purpose (distribution, rectifier, arc furnace, amplifier output, etc.).
- By ratio of the number of turns in the coils
- Step-up. The secondary has more turns than the primary.
- Step-down. The secondary has fewer turns than the primary.
- Isolating. Intended to transform from one voltage to the same voltage. The two coils have approximately equal numbers of turns, although often there is a slight difference in the number of turns, in order to compensate for losses (otherwise the output voltage would be a little less than, rather than the same as, the input voltage).
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- Variable. The primary and secondary have an adjustable number of turns, which can be selected without reconnecting the transformer.
IV. Find Ukrainian equivalents to the words:
saturation, skin-effect, over-excitation protection, impedance matching, circuit isolation, rectifier, amplifier output, step-up transformer, step-down transformer, isolating transformer, variable transformer, power frequency.
V. Point out English equivalents to the words:
, , , , , , , , , , .
