Technical explanations
Eltra Elektromaschinen- und Transformatorenbau GmbH
The rated ambient temperature is the maximum temperature at which the transformer may be operated continously under normal conditions of use. The power output values stated in our catalog hold for ambient temperature of 40°C.
Transformers with cooling channels must be vertical. Ventilation must be free of obstruction.
All transformers are rated, if not otherwise specified, so that the rated output is achieved at rated supply voltage, rated frequency, rated output current and rated power factor cos phi = 1. For three phase supply, the rated voltage is the phase-to-phase voltage.
All transformers listed here are suitable for use with a rated frequency of 50 – 60 Hz. On the rating plate of the standard transformer, there are two frequency 50 Hz and 60 Hz and the rated output is equal. On request, we can produce transformers with a frequency up to 1 kHz.
The nominal rating specification in the catalog relate to the operating mode Continuous Operation (CO). In most cases with shorter loading times, Intermittent Operation (IO), a transformer with a lower unit rating can be used.
The time of operation for transformers is the relationship between load time and duty cycle time. The duty cycle time is limited to 10 minutes. The reduction factor in the following table states the permissible reduction of the transformer in relation to continous operation.
The time of operation in % can be calculated with the following formula:
ED% = (Operating time / Duty cycle time) x 100%
ED % | Factor |
100 | 1 |
---|---|
80 | 0,89 |
70 | 0,85 |
60 | 0,77 |
50 | 0,7 |
40 | 0,63 |
30 | 0,55 |
20 | 0,45 |
Example:
Rated power: 200 VA
Operating time: 6 minutes
ED = 6 / (6+4) x 100% = 60%
Type :
200 VA * 0,77 = 154 VA
The power is: 154 VA
That`s the type: 160 VA
It should be noted that the voltage drop increases in proportion to the relationship between the nominal rating and the unit rating.
The protection type indicated by IP xx , specifies protection against foreign bodies, contact and water ingress. The definitions of the individual characteristic numbers are stipulated in DIN 40050.
Examples:
IP 00
no special protection
IP 20
IP 23
IP 54
The transformer, reactors and power supply units are designed for installation up to 1000 m above sea level. When installed at sites higher than 1000 m, the loading must be reduced. The values for a rating are stated in the following table.
Installation at altitudes m | Power reducing factor |
1000 | 1 |
---|---|
1500 | 0,97 |
2000 | 0,94 |
3000 | 0,90 |
4000 | 0,85 |