Specifications

T4.33
Transformers
T4
One combined vs. two separate secondary
windings or voltages
In a transformer with one combined secondary
winding for 2 voltages, obviously the cross section
of the wire is the same for the whole secondary
winding. The different output voltages are derived
by connecting at different places of the one
secondary winding (see fig.3).
As a consequence, the output power is different for
the different output voltages.
Let’s assume the power of the transformer in figure
3 being 15VA and two secondary voltages being 12
and 8V. Obviously, the maximum output power that
the transformer can deliver is directly depending on
the maximum current that may flow through the
secondary winding, the latter one being limited by
the cross section of the wire.
In this example here, the cross section of the
wire used in the secondary winding is such that a
current, maximum equal to 1.25A, may flow at all time,
generating an output-power of 12 x 1.25 = 15VA. For
the 8V output, as the cross-section of the wire is the
same as for the 12V output, so is the maximum current
! This means that in this case, the maximum output
power is reduced to 8 x 1.25 = 10VA.
In a transformer with separate secondary
windings, there exists one winding per output
voltage (see fig.4).
This allows different cross-sections for both
secondary winding wires, making it possible to
have the nominal output power at all the different
output voltages.
Except for the 666650, 666651 and 666652, all
Series T safety and bell transformers have their
nominal power present at all output voltages.
Features and benefits
In figure 5, the front views of the 2 and 4
module Series T transformers are shown.
As always, the main characteristics of the device
are printed in the upper part
1 .
These are:
- Output power
- Nominal rated primary voltage
- Secondary voltages
- Wiring diagram
- 6 digit ordering code.
From the point of view of output power, a complete
range is available: 5, 10, 15, 25, 40, and 63VA, as
bell transformer for an output power up to 25VA and
as safety transformer from 15VA and up.
The range also includes a bell transformer with
integrated on-off switch, a buzzer with integrated
transformer, modular bells and modular buzzers on
24V as well as on 230V.
All Series T transformers are short-circuit proof, the
666650, 666651 and 666652 by construction, all the
others by means of a PTC
All Series T transformers have double isolation and
except for the 666650, 666651 and 666652, all have
the rated output power at each output voltage.
As always, the function of the transformer or the
circuit that it supplies with power can be indicated
behind the circuit indicator
2 i.e. bell front door,
power supply contactors, … .
The clearly marked Pozidriv terminals
3 are all
captive.
fig.4
fig.5
fig.3
1
2
3
3
2