Hidrostal A2Q - Temperature monitoring: Bimetal switch or PTC probe

4 | Design and functions
20 / 49 Hidrostal AG
1
2
3
1 Coil head with integrated temperature limiter (bimetal switch or PTC
probe, option)
2 Moisture sensor (BN3, BK3 only; option)
3 Temperature limiter installed in the cable cover (bimetal 80°C, not
available for A2Q)
NOTICE
Improper electrical connection.
Risk of damage to property!
• Never connect a PTC probe to more than 2.5V.
Temperature monitoring:
Bimetal switch or PTC
probe:
Temperature monitoring sensors protect the electric motor winding against
excessive temperatures. Bimetal switches (NC) and thermistors (PTC) are
used. In contrast to bimetal switches, thermistors are still able to protect the
electric motor when the rotor is blocked and start-up is sluggish.
Three 150°C bimetal switches are installed in the top coil head and
connected in series. The top coil head also holds three 150°C thermistors
connected in series. Each phase has one sensor of each kind. Depending
on the configuration, the connection cables of the sensors are provided via
the control cables.
The temperature monitoring sensors, such as the bimetal switches or
thermistors, always need to be evaluated by the electronic evaluation
system. Bimetal switches can be connected to a certified electronic
evaluation system or directly to the control unit (max. 250VAC, 2.5A).
Thermistors must only be operated and evaluated with a certified electronic
evaluation system. Thermistors always need to be employed for temperature
monitoring during frequency converter operation. In this case, they can be
directly connected to the frequency converter.