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- Overloads.
- High travelling speed of the cursors with total run in less than 3 seconds).
- Too long connecting cables or forming loops.
• The equipment should be serviced properly (see paragraph 5).
The design engineer or fitter should take account of these danger advises and take the necessary precautions to
overcome them.
He has to foresee installing some mechanical and electrical protections and eventually placing notices clearly
visible to the personnel involved.
The installation's safety in charge, should verify that the primary safety requirements are being fulfilled, during the
transportation, installation, commissioning, operating and servicing.
2.-
CHARACTERISTICS.
Input voltage Up:
Supply voltage for which the variable transformer has
been designed. The standardised single phase voltage
is 230 V
The standardised three phase voltage is 3 x 400 V.
Output voltage Us:
The output voltage is obtained though the brush, being
able to take as many values as turns are provided on the
variable transformer's core. The maximum voltage is
obtained with the cursor on the opposite end to the
input.
Us = 0 ÷ Up.
Rated current In:
This is the current which can be supplied for any output
voltage.
Maximum current Imax:
This is the current which can be supplied for the mains
rated voltage (fig. 1).
Rated power Pn:
Px = in x Us max.
Permissible momentary overloads Ks:
The variable transformer's rated current can be exceed-
ed during very short period of time; The curve of Fig. 2
shows the Ks coefficient values dependent to the over-
load length. Overload current:
Is = In x Ks.
Fig. 1. Us in % of Up.
Fig. 2. Time in seconds.
Fig. 3. Environment temp. in ºC.
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