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If only one voltage is indicated on the nameplate together with the delta sign, the
motor can be switched on directly at the indicated voltage or with a star/delta
starter.
Pole change motors (for two or more speeds) are connected according to a diagram
sent together with the motor.
6
Putting into service
Before putting a motor into service, one should check especially when the motor has
not been used for a long time that the insulation resistance of the winding is
sufficient. The insulation resistance has to be at least 1.000
Ω
per Volt, what means at
least 400.000
on a supply voltage of 400V.
If the insulation resistance is not high enough, the motor has to be dried out
revarnished or rewound. Check all connections and adjust the thermal protection
units to the correct current. Switch the motor on in a no load state to determine the
direction of rotation. Load the motor gradually and check whether it runs without
vibration. The motor can be used under a variation of the main voltage ± 5% or
frequency variation of max. ± 2% compared to the nominal frequency or nominal
voltage, in compliance with the international regulations for electric machines.
7
Maintenance
The totally enclosed and fan cooled three phase squirrel cage induction motors
require very little maintenance. Nevertheless it is recommended to check the motor
regularly in order to prevent a breakdown caused by dust, moisture, vibrations, too
much or too little greasing.
7.1
Dust
The outer parts of the totally enclosed motors, especially the cooling ribs or cooling
channels, have to be kept as clean as possible in order not to obstruct the cooling air
from the fan extracting the heat from the motor frame.
7.2
Moisture
Motors that are stalled for a long time, should be started from time to time to
prevent moisture affecting the windings in the long term. Before putting the motor
into service, one should check especially when the motor has not been used for a
long time that the insulation resistance of the winding is sufficient.
