# Terms and Definitions

Compliance with the relevant standards goes without saying for trafomodern, testing of devices produced by other manufacturers have however revealed that this does not apply to all of our competitors. In the following you will find an explanation for some terms and definitions.

Nominal values are always rated values. Rated values are rated voltage, rated current (rms values), rated output, rated frequency and rated turns ratio. Together these values uniquely define a transformer.

The supply voltage (in the event of three-phase systems between the outer conductors), assigned to a transformer under defined operating conditions.

The frequency assigned to a transformer under defined operating conditions.

The output current at rated input voltage and rated frequency, assigned to the transformer for the set operational conditions.

The output voltage (for three phase systems between the outer conductors) at rated input voltage, rated output current and rated power factor (normally power factor cos f = 1), assigned to the transformer for the set operational conditions.

The product of the rated output voltage and the rated output current, for three-phase systems multiplied by v3.

Power Factor cos f indicates the ratio of apparent power (U*I) being available as active power with sinusoidal variables. In ideal systems there is an angle of exactly 90 degree between current and voltage, there active power is therefore 0 and the reactive power is the same as the apparent power. However in reality the angle is a little bit smaller than 90 degree, hence there will be always a small part of active power (=power loss), which might be very small but still there.

The highest temperature at which a transformer can be used in accordance with the prevailing operating conditions for continuous operation.

The input power of the off-load transformer at rated input voltage and rated frequency.

Active input power, when the output side of the transformer is short-circuited and the rated (nominal) output current is flowing.

The short-time rating is the output at the secondary side of a control transformer with cos f= 0,5 and a maximum voltage drop of 5% vs. the rated (nominal) output voltage.

The output voltage of an unloaded transformer at rated input voltage and rated frequency.

The current at the input side of an unloaded transformer at rated (nominal) input voltage and rated frequency.

The voltage to be applied to the input winding in order to obtain the same current as the rated output current while the output winding is short-circuited and the windings are at ambient temperature. The value is given as a percentage of the primary rated input voltage. The uk is almost in correlation with the no-load-behaviour of the transformer.

**Rated Values:**Nominal values are always rated values. Rated values are rated voltage, rated current (rms values), rated output, rated frequency and rated turns ratio. Together these values uniquely define a transformer.

**Rated Input Voltage (Nominal Input Voltage):**The supply voltage (in the event of three-phase systems between the outer conductors), assigned to a transformer under defined operating conditions.

**Rated Frequency (Nominal Frequency):**The frequency assigned to a transformer under defined operating conditions.

**Rated Output Current (Nominal Output Current):**The output current at rated input voltage and rated frequency, assigned to the transformer for the set operational conditions.

**Rated Output Voltage (Nominal Output Voltage):**The output voltage (for three phase systems between the outer conductors) at rated input voltage, rated output current and rated power factor (normally power factor cos f = 1), assigned to the transformer for the set operational conditions.

**Rated Power (Nominal Power):**The product of the rated output voltage and the rated output current, for three-phase systems multiplied by v3.

**Power Factor cos f:**Power Factor cos f indicates the ratio of apparent power (U*I) being available as active power with sinusoidal variables. In ideal systems there is an angle of exactly 90 degree between current and voltage, there active power is therefore 0 and the reactive power is the same as the apparent power. However in reality the angle is a little bit smaller than 90 degree, hence there will be always a small part of active power (=power loss), which might be very small but still there.

**Rated Ambient Conditions ta:**The highest temperature at which a transformer can be used in accordance with the prevailing operating conditions for continuous operation.

**No-load Output (= No Load Losses = Core Losses):**The input power of the off-load transformer at rated input voltage and rated frequency.

**Short-circuit Losses (= Copper Losses):**Active input power, when the output side of the transformer is short-circuited and the rated (nominal) output current is flowing.

**Short-time Rating:**The short-time rating is the output at the secondary side of a control transformer with cos f= 0,5 and a maximum voltage drop of 5% vs. the rated (nominal) output voltage.

**No-load Output Voltage:**The output voltage of an unloaded transformer at rated input voltage and rated frequency.

**No-load Current:**The current at the input side of an unloaded transformer at rated (nominal) input voltage and rated frequency.

**Short-circuit Voltage uk:**The voltage to be applied to the input winding in order to obtain the same current as the rated output current while the output winding is short-circuited and the windings are at ambient temperature. The value is given as a percentage of the primary rated input voltage. The uk is almost in correlation with the no-load-behaviour of the transformer.