Question:
What must be observed with regard to 'Protection against electric shock' when connecting temperature sensors (PT1000, KTY, PTC, TCO,...) to the controller?
Answer:
In order to protect persons against electric shock, a "safe isolation" of the existing potential is required. There must, in particular, be no conductive connection between the potential of the 24-V electronics supply and the high voltages in the inverter/motor. Components that may be touched by persons must not come into contact with dangerous voltage. Even if an insulation fault occurs.
A simple insulation (basic insulation) is not adequate according to corresponding standards: EN 61800-5-1, EN 50178, EN 60204-1:2006.
For the required "safe isolation" the potential separation must be designed as follows (over the entire circuit between device and temperature sensor):
Available connections for temperature sensors:
Lenze device series
| Feedback system input
| PTC input (T1, T2)
|
Servo inverter i700
| X7 / X8
| ---
|
Servo inverter i750
| X7 / X8
| X109
|
Servo inverter i950
| Motor feedback module (A)
| X109
|
Inverter drives i510
| --- | --- |
Inverter drives i550
| ---
| X109
|
Servo drives 9400 HL
| X7 / X8
| X106
|
Inverter drives 8400 TL
| X7 / X8
| X106
|
Encoder input (X7/X8) / Motor feedback module (A):
The encoder input is located on the safely separated potential of the control electronics so that all signal cables connected to it can be safely touched. In order to maintain the safe isolation, the temperature sensors in the motor must be appropriately isolated from the dangerous potential of the mains and motor phases. The cables, terminals, plug-in connectors, and the cable routing must also ensure the safe isolation (double or reinforced insulation).
For the Lenze servo motors, KTY and PT1000 are by default designed with reinforced insulation and the encoder cable (not the motor cable) is used for connecting them to the controller. This ensures a safe isolation in the Lenze system.
If a motor without feedback system is to be used, you can also use a separate temperature sensor cable for the connection to the encoder input.
Important: For Lenze motors, temperature contacts (TCO) and simple PTC sensors are not installed with reinforced insulation. Therefore they cannot be connected via the encoder input.
A connection to the encoder input via the cores in the motor cable is not possible because the electrical isolation of the plug-in connectors at the motor is not sufficient.
PTC input (T1,T2):
Inside the devices, the PTC input (T1,T2) is designed with a basic insulation.
This is why, an additional isolation in the form of a basic insulation is required outside the devices, from the sensor to the PTC input.
For all Lenze motors, the temperature sensors inside the motor are at least equipped with a basic insulation. In this way, all temperature sensor types installed in Lenze motors can be connected to the PTC input (T1,T2).
Motor and PTC input can be connected via the cores in the motor cable.
The i700 servo inverter series is not equipped with a PTC input. Therefore, TCOs and pure PTCs cannot be directly connected.
In this case, a separate PTC evaluator can be used to evaluate the temperature sensor in order to achieve the required safe isolation. PTC evaluators can be purchased on the free market.
KTY and PT1000 temperature sensors, temperature contacts (TCO) and PTC temperature sensors:
Lenze servo motors are equipped with KTY and PT1000 temperature sensors as well as with sensor combinations (KTY+2xPTC) and (PT1000+2xPTC).
The are installed with a reinforced insulation.
That's why they are suitable for connection via the encoder input (X7/X8) of i700 and the Motor feedback module (A) of i950.
Lenze motors without a feedback system are equipped with TCOs and pure PTCs normally.
These sensors are not designed with a reinforced insulation in the motor.
Therefore, they can only be directly connected to a sensor input that is at least equipped with a basic insulation such as the PTC input (T1,T2), but not the encoder input (X7/X8) / Motor feedback module (A).
- For motors of other manufacturers the same restrictions apply accordingly.
Application of temperature sensors:
Keywords: Double basic insulation, with double basic insulation, reinforced insulation, with reinforced insulation, protection of persons, electric shock, temperature contact, thermal contact, NC contact, normally-closed contact, protective insulation, protection against accidental contact, protection against contact
