Equipment/ functions - Process Valve Solutions
Equipment/ functions - Process Valve Solutions
Equipment/ functions - Process Valve Solutions
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Motor protection<br />
In order to protect the motor against<br />
overheating thermoswitches or PTC<br />
thermistors are embedded in the<br />
motor windings of the 3-phase AC<br />
and 1-phase AC motors. When integrated<br />
into the control circuit, they<br />
will protect the motor against damage<br />
due to excessively high winding<br />
temperature.<br />
Thermoswitches and PTC thermistors<br />
offer better protection than thermal<br />
overload relays, since the temperature<br />
rise is directly measured at<br />
the motor.<br />
The thermoswitches will interrupt the<br />
control circuit as soon as a winding<br />
temperature of 140 °C is exceeded.<br />
After cooling down to a temperature<br />
between 120 °C to 90 °C, the actuator<br />
can be switched on again.<br />
Motor temperature<br />
140 °C<br />
115 °C<br />
90 °C<br />
Tripping point<br />
Time<br />
Reset point<br />
Important! Failure to integrate the<br />
motor protection device into the controls<br />
voids the warranty for the<br />
motors.<br />
If the actuator is equipped with integral<br />
controls, the thermoswitches<br />
are automatically integrated.<br />
Delay time<br />
The delay time is the time from the<br />
tripping of the limit or torque switches<br />
to the motor power being removed.<br />
To protect the valve against excessive<br />
peak torques, the delay time<br />
should be as low as possible. This<br />
should be taken into account, especially<br />
if the actuators are controlled<br />
by a PLC. We recommend a delay<br />
time < 50 ms and to switch off the corresponding<br />
contactor directly by the<br />
limit or torque switch. Longer delay<br />
<strong>Equipment</strong>/ <strong>functions</strong><br />
times are possible provided the output<br />
speed, output drive type, valve<br />
type and the type of installation are<br />
considered.<br />
For the AUMA MATIC and AUMATIC<br />
integral controls the motor will immediately<br />
be switched off after tripping<br />
of a switch.<br />
Actuator type Thermoswitches PTC thermistors<br />
SG/SGR 05.1 – SG/SGR 12.1 1)<br />
Standard Option<br />
SGExC 05.1 – SGExC 12.1 1)<br />
Option Standard<br />
1) Also available with integral controls AUMA MATIC or AUMATIC; in this case the PTC tripping<br />
device is already integrated, if PTC thermistors are used.<br />
Rating of the thermoswitches<br />
AC voltage<br />
Switch rating<br />
(250 V AC)<br />
Imax<br />
cos ϕ = 1 2.5 A<br />
cos ϕ = 0.6 1.6 A<br />
DC voltage Switch rating<br />
Imax<br />
60 V 1 A<br />
42 V 1.2 A<br />
24 V 1.5 A<br />
17
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