Specifications

T4
T4.9
Contactors
fig.8A
Endurance curve
(Operations vs. switching-off current)
AC-1/400 V 3- for CTX 24, 40, 63
AC-1/230 V 1- for CTX 20
fig.8B
Endurance curve
(Operations vs. switching-off current (kW))
AC-3/400 V 3- for CTX 24, 40, 63
AC-3/230 V 1- for CTX 20
Example
An electrical heater (4.4kW, 230V, single phase) is
used for 200 days per year. As an average, the
thermostat switches 50 times a day on and off
(= 100 operations).
The total number of operations per year is 20000
(200 days x 100 operations/day).
The current this heater draws is roughly 20A.
In this case,
- a 20A contactor will operate for 7.5 years
(150000 / 20000),
- a 24A contactor will operate for 9 years
(180000 / 20000),
- a 40A contactor will operate for 15 years
(300000 / 20000),
- a 63A contactor will operate for 27 years
(540000 / 20000).
General remarks
- Using contactors at low voltage, and especially
when several devices can be operated
simultaneously, ultimate care should be taken to the
correct dimensioning of the step-down transformer.
- When several adjacent contactors are continuously
energised (1 hour and more), the heat dissipation
could influence the correct operation in a negative
way. To avoid this, a spacer module should be
installed between every third and fourth device
(type designation CTX SP). This is not applicable
for the 20A-contactors.
Text for specifiers
- Contactors all have a silent operation and
therefore are preferably equipped with a DC-coil.
- An internal bridge rectifier allows the contactor to
be used on AC (from 40 to 450Hz)as well as on
DC (except for the 20A-contactor).
- The capacity of the load-terminals is from 1.5 to
10mm
2
.
- The capacity of the control-terminals is from 0.5
to 4mm
2
.
- The contactors are equipped with a flag which
indicates the position of the coil (contacts).
- The protection-degree of the contactor is IP20.
- The devices are modular and DIN-rail mountable.
- Auxiliary contacts as well as spacers for heat
dissipation are available.
- The power-supply voltage is allowed to vary in the
range of 106%xUn …. 80%xUn without
influencing the correct operation of the device.
- Day-Night contactors are available; these
contactors have a 0-Auto-1 switch for manual
operation. This switch cannot be blocked in the
1-position.
- The contactor is equipped with a transparent
circuit indicator.
Endurance
In general, the guaranteed number of operations at
nominal load in AC1 is called the electrical service life.
The Contax and Contax DN contactors all have an
electrical service life of 150000 operations (Note:
1 cycle = NO → NC → NO = 2 operations).
However, if the load of the contactor is less than its
nominal load, also the erosion of the contacts will
be less and as a consequence, the electrical service
life will increase.
The graphs in figure 8 show the relation between
the number of operations and the maximum load
allowed to obtain this life expectancy.