NORD Drivesystems B1091 - Manual (Page 6)

-6- B1091-GB-4613 www.nord.com
3. Information
Refer to the table below for the tightening torques of the screw connections of electric
terminals and the terminal board connections (apart from terminal strips):
Tightening torques for terminal board connections
Thread diameter M4 M5 M6 M8
Tightening torque (Nm) 0.6 – 1.2 1.8 – 2.5 2.7 – 4.0 5.5 – 8.0
If the machine has an standstill heater, it must not be switched on during operation.
3.6 Checking the insulation resistance
Before putting the motor into operation for the first time, after a lengthy period of storage or
standstill (approx. 6 months), the insulation resistance of the winding must be determined.
During and immediately after the measurements, the terminals carry dangerous voltages and
must not be touched.
Insulation resistance
The insulation resistance of new, cleaned, repaired windings against the housing and against
one another is >200 M
Ω.
Measurement
In the case of windings up to an operating voltage of 400 V the insulation resistance against
the housing must be measured with a DC voltage of 500 V. At operating voltages up to 725 V
measure with a DC voltage of 1000 V. For this the temperature of the windings should be
25°C ± 15°C.
Checking
In the case of a new, cleaned winding or a repaired motor which has been stored or shut
down for any lengthy period, if the insulation resistance of the winding against the housing is
less than 50 M
Ω, the cause may be moisture. The windings must then be dried.
After a lengthy period of operation the insulation resistance may reduce. As long as the
measured value does not fall below the critical insulation resistance of < 50 M
Ω, the motor
may continue to be operated. If the value falls below the critical level, the cause must be
established and if necessary, the windings or winding sections must be repaired, cleaned or
dried.
3.7 Commissioning
Note: Electromagnetic compatibility
Production of interference: In case of large torque differences (e.g. when driving a piston
compressor) a non-sine wave motor current is induced, whose harmonics can cause an
impermissible effect on the mains and therefore impermissible production of interference.
With supply by frequency inverters, various strengths of interference are produced according
to the design of the frequency inverter (type, interference suppression, manufacturer).
The EMC information of the inverter manufacturer must be observed. If the manufacturer
recommends the use of a screened motor supply lead, screening will be most effective if it is
electrically connected to a large area of the metal terminal box of the motor (with EMC cable
gland made of metal). In the case of motors with built-in sensors (e.g. PTC thermistors)
interference voltages due to the inverter can occur in the sensor line.
Interference immunity: In the case of motors with built-in sensors (e.g. PTC thermistors) the
user must ensure adequate interference immunity by selecting a suitable sensor signal cable
(possibly with screening and connection as with the motor supply cable) and the evaluation
device. Prior to commissioning always observe the information and instructions in the
operating manuals for inverters as well as all other instructions. After installing the motors,
check them to make sure that they are operating correctly! In the case of brake motors also
check that the brake operates correctly.