electrical transformer 101

Distribution Transformers are designed to have maximum efficiency at ___ of the operating load

• 10%

• 50%

• 85%

• 95%

Answer explanation

The distribution transformer is used for the distribution of electrical energy at low voltage as less than 33KV in industrial purpose and 440v-220v in domestic purpose. It work at low efficiency at 50-70%, small size, easy in installation, having low magnetic losses & it is not always fully loaded.

Electrical Transformer can able to Transform both AC and DC Voltages in a Circuit

T/F

• True

• False

Answer explanation

It can convert high and low voltages, it cannot convert AC to DC. But they can be used as a component in a larger system that does convert AC into DC

Scott Connection is used to Convert which of the following

• Three Phase to Six Phase

• Three Phase to Two Phase

• Three Phase to Twelve Phase

• Three Phase to Single Phase

Answer explanation

The Scott-T Connection is the method of connecting two single-phase transformers to perform the 3-phase to 2-phase conversion and two-phase to three-phase conversion.

Generally Transformer Taps shall be present in which of the following side

• HV (high voltage)

  side

• LV (low voltage)

  side

Answer explanation

There are some reasons for tapping on the high voltage side of the large transformer which are, In large transformers, the high voltage(HV) winding is generally wound over the low voltage (LV)winding for insulation saving purpose

Which of the following insulation class will withstand high temperature in Transformer

• A

• B

• F

• H

If one were to ask people in the electronics industry how device temperature and reliability are related, it is likely that the most common response would be something along the lines of “the rule of thumb is that every 10°C increase in temperature reduces component life by half”

T/F

• True

• False

In an electrical transformer, High Voltage (HV) side will have more number of turns

(more coils of wire) than the Low voltage (LV)

T/F

• True

• False

Which of the following is not a necessary requirement to operate two Transformers in parallel

• Same kVA rating

  (Kila Volt Amps is simply 1,000 volt amps)

• Same Polarity

• Same X/R rating

  (the amount of reactance X divided by the amount of resistance R)

• Same identical Tap ratings

CRGO (cold rolled grain orientated) Core material is used in Electrical Transformers in order to reduce which of the following

(Choose 2)

• Stray Loss

• Hysteresis Loss

• Eddy Current Loss

• Copper Loss

Answer explanation

CRGO laminations in a transformer are used to minimize both eddy current and hysteresis losses.

Transformer Oil acts as Coolant but NOT as Insulating Medium

• True

• False

Answer explanation

Transformer oil or insulating oil is an oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers (wet transformers)