Connection Of The Motor - Siemens 1LA8 Series Operating Instructions Manual

3.6 Connection of the motor

Overview
Danger
All work on the motor must only be performed
by qualified personnel, with the motor in a
stationary state. The supply should be secured
so that it cannot be switched back on again.
Check that no voltage is present before
commencing work.
The type designation of the terminal box for
connecting the power cables can be found in the
section entitled "Technical data"; refer to the spare
parts list entitled "Main terminal box" for a diagram of
the terminal box. Connecting cables can be sealed and
secured at every entry point into the terminal box.
Suitable entry plates can be rotated through 180°.
The necessary connection data regarding
• The direction of rotation,
• The number and arrangement of the terminal
boxes,
• The circuit and connection of the motor winding
are specified in the section entitled "Technical
data".
The permissible direction of rotation can also be seen
on the motor rating plate.
Examine the rating plate data and ensure that it
matches with the power circuit to which the motor is
to be connected. Check to see that system voltage and
frequency agree with the data given on the rating
plate. Select the size of supply cables as required for
the particular current rating. Connect the supply
cables in accordance with the connection diagram
shown inside the terminal box cover.
Connection and arrangement of the terminal links
must agree with the diagram provided in the terminal
box.
Before closing the terminal box ensure that:
– Interior of the terminal box is clean and free of
cable residue.
– All terminal screws and bolts are firmly tightened.
– Minimum air-clearance (>10mm upto 500V.
>14mm upto 1000V) is maintained.
– Unused cable entries are sealed off with the
plugging elements firmly screwed in.
– All sealing surfaces have adequate contact.
When the motors are provided with anti-condensation
heaters, ensure that the supply to heaters is switched
off before switching on the motor.
Before starting and during operation, make sure that
all the relevant safety and statutory regulations
pertaining to the area of operation are complied with.
Earthing
Connect the earthing conductor to the terminal with
the earth marking in the Terminal box as well as on the
Stator housing.
Clean the area underneath the earthing terminal and
smear it with petroleum jelly before making earthing
connections.
Checking the insulation resistance
The insulation resistance of the windings must be
measured prior to initial startup of the machine, and
after long periods of storage or standstill
(approximately 6 months).
Warning
While the measurement is being taken and
immediately afterwards, some of the terminals
carry dangerous voltages and must not be
touched.
Measurement
The insulation resistance of the windings to ground is
measured with 500V DC. The winding temperature
should be 30ºC±15ºC.
Checking
Minimum insulation resistance value (at 40°C) as
specified in IS: 4722 is Rm =kV + 1, where kV is the
rated voltage of the machine. Thus, for 415V rated
voltage the insulation resistance of the winding should
not be less than 1.42 MOhm.
If less the winding must be suitably dried as per IS: 900
Connecting
Note
Ensure that there is a safe and reliable PE ground
connection before starting any work.
The connection must be made in such a way that a
permanent, safe electrical connection is maintained
(no protruding wire ends). Use the matching cable end
pieces. Depending on the parts fitted, the connecting
parts may be suitable for connection with or without
cable lugs.
In some cases a terminal strip is installed in the main
terminal box for the auxiliary circuit connections. The
connecting terminals of the auxiliary circuits are
suitable for cable cross-sections of up to 1.5 mm
(fine-wire) or 2.5 mm (single-wire). On conductors for
2
auxiliary terminals, the length of insulation, which
needs to be stripped, is approximately 6 to 9 mm
depending on the terminal type. When this length is
correct the conductor reaches right into the terminal
as far as it can go while the wire insulation reaches the
contact part of the terminal.
2
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