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On Site Motor Drying |
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Resistive Induction Motor Heater |
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Introduction |
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Electrical motors, Generators & Transformers may suffer permanent damage when energized whilst the internal insulation is compromised due to moisture ingress from flooding or other circumstances.
Newly wound windings require Gliptol or any varnish applied to the windings to increase the insulation level as well as prevent, to some extent the ingress of moisture. Both the above cases require the windings of the motor to be baked in order to obtain the required temperature for drying or curing of Gliptol.
This is a costly and time-consuming activity. Our Resistive Induction Motor Heater provides a cost-effective and fast means of removing all moisture from the above mentioned.In addition, the equipment and process may also be used to rapidly cure externally applied Gliptol or any other Varnish, used to increase the insulation level and prevent the ingress of moisture. |
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Benefits |
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The following benefits are obtained through the utilization of our Resistive Induction Motor Heater. |
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- Heating of induction motors in situ (on site or where it is positioned),
eliminating
the need for dismantling from couplings and re-alignment of motor.
- Significantly reduced drying time for wet motors.
- In-situ (on site or where positioned) bearing replacement whilst motor dries.
- Drying of any number of motors connected in series.
- Increased facility output.
- Significantly reduce curing time for Gliptol or Varnish.
- No oven needed.
- No need to transport large motors off-site
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Principle of Operation |
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The stator windings of an induction motor or generator have an intrinsic
resistance in the copper wire. By injecting a current into the windings, power will be dissipated in the windings, leading to a buildup of heat.
The current to be injected into the stator windings, is generated by the power electronic stage. The purpose of this stage is to ensure that the applied voltage on the stator windings is a fraction of the rated voltage of the motor to be heated. This will prevent internal electrical failure during the heating process (should the internal insulation have been compromised due to moisture)
As none of the normal cooling mechanisms on an operational induction motor are functional during the heating process, the heat buildup in the windings will occur rapidly, enabling the removal of moisture through evaporation or the curing of Gliptol through the application of heat.
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Internal Insulation Integrity |
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A motor internal insulation test (megger test) will indicate the impedance between the motor windings and the case of the motor, as well as between the three windings, at a high voltage, depending on equipment input voltage.
A relatively low impedance will indicate a damp condition of the motor and would increase the risk of an internal electrical failure, should the motor be energized at rated voltage.In order to prevent permanent damage the moisture needs to be removed from the induction motor stator windings. This will result in a required high internal insulation resistance.
It is therefore proposed that the insulation resistance be used as a means of determining the condition of the stator windings with respect to moisture content. Field tests indicated that an insulation resistance of more than 10MΏ (measured at 1000V), is sufficient for safe energization of the stator windings. |
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