Medium voltage drive controlled as a motor heater

Abstract

Aspects of the present disclosure generally relate to the technical field of electric motors and motor drives. More specifically, an electric motor connected to a motor drive is described, wherein the motor drive is configured to operate a motor winding of the electric motor as a heater, such that condensation is prevented from building up on the motor winding.

Description

[0001] MEDIUM VOLTAGE DRIVE CONTROLLED AS A MOTOR HEATER

[0002] BACKGROUND

[0003] In outdoor intexmittent motor applications, there are certain operation, storage and maintenance practices that must be observed. It is imperative that a motor space heater is turned on anytime that a motor is not being operated. In addition, if the motor is not in operation for over 30 days, than even operating the space heater is not enough to assure that condensation has not built up on the motor winding. Before the motor can be safely energized, motor insultation tests must be conducted to assure that the winding is clean and dry. These tests are not convenient as they require that the motor be physically disconnected from the power source. Although all motors require these tests, open motor enclosures, such as a WPII enclosure (weather protected type II), are at significantly more risk than totally enclosed enclosures, such as a TEAAC (totally enclosed air-to-air cooled) or TEW AC (totally enclosed water-to-air cooled), to have condensation build up on the motor winding surface.

[0004] WPII motors rely on drawing in external environmental air to cool the motor during operation. Unfortunately, even when the motor is not in operation, a WPII enclosure allows the external environment air to blow through the internal motor components. Under certain conditions, the external environmental air that enters a motor, results in condensation being formed on the winding coil surface. Motors have space heaters that are designed to keep the internal motor components at a temperature that is at least 5°C warmer than the air dew point. However, with wildly varying weather conditions (such as large day to night temperature swings, severe wind, high humidity, etc.) this can be difficult to achieve with a fixed and low power motor space heater. Over the short term, even when the 5 ®C minimum separation margin is not maintained under extreme weather conditions, the moisture does not build up on the winding to a sufficient degree to cause an issue. However, under longer term (i.e. longer than 30 days) periods of non-operation. the moisture built up on the winding surface may build up to unacceptably high levels. The motor space heater only prevents moisture from condensing under most conditions, but not all. Furthermore, the moisture accumulates to progressively higher levels as the space heaters are not powerful enough to drive out any moisture that has previously accumulated. Eventually enough moisture has accumulated, and the winding Is ‘wet’ and must be properly dried out.

[0005] DETAILED DESCRIPTION

[0006] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure.

[0007] In accordance with an embodiment of the present disclosure, a method is disclosed that provides variable, high power, controlled motor heating by using a motor drive, such as a medium voltage drive, to create losses within the motor while not allowing any shaft rotation because a generated torque is lower than a rotor’s breakaway torque. With the drive continuously monitoring motor winding temperature sensors and then controlling current and voltage injected into the motor, it will be possible to maintain more than just the minimum 5°C temperature margin while assuring that a stator of the motor does not overheat. With the controlled, high-power heating, this heating can be delivered even in extreme weather conditions thus assuring that a motor winding is always above an air dew point. This in turn results in no condensation on the motor winding. Thus, with this heating technology, even with the motor non-operational for an extended period, it will be safe to energize the motor without requiring insulation tests as currently required.

[0008] Features of the proposed solution are:

[0009] ■ Motor winding temperature continuously controlled to assure that it is maintained above the dew point of the surrounding air to assure that condensation does not build up on the winding surface. - The method can provide the ability to inject an adjustable amount of heat into the motor, which can result in a controlled and verifiable increase in temperature,

[0010] - The amount of heat created by the winding can be significantly higher than the traditional fixed power motor space heater. The high-power heating is controllable thus the motor winding is not at risk of being overheated. In open motor enclosures this is particularly important as under adverse environmental conditions (large daily temperature swing, high humidity, and windy conditions) the traditional motor space heater may not be able to provide a sufficient amount of heat,

[0011] - This technology has a particular advantage for open motor enclosures (such as a WPII) and will enable this type of enclosure to be used in intermittent applications more readily than has been safely possible without this heating technology''. This is significant as open motor enclosures are desirable as the motors are significantly less costly than more robust totally enclosed enclosures (such as TEAAC or TEWAC).

[0012] Software to allow motor drive to operate as a motor heater: Drive application softwarecan be setup to configure the drive to effectively create losses as a motor heater while not allowing any shaft rotation. Multiple options exist to create losses in the motor. These are: a) operate at high frequency and low voltage, b) operate at very low frequency and nominal current, and c) run with DC voltage.

[0013] While embodiments have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the disclosure and its equivalents, as set forth in the following claims.

Claims

CLAIMS1 . A system comprising: an electric motor connected to a motor drive, wherein the motor drive is configured to operate a motor winding of the electric motor as a heater, such that condensation is prevented from building up on tire motor winding.

2. The system of claim 1. wherein the motor drive is configured to operate the motor winding as a heater w'hen the electric motor is non -opera lion al or inactive.

3. The system of claim 1 , wherein a motor winding temperature is controlled and monitored to assure that the motor winding temperature is warmer than a dew point temperature of surrounding air,4. The system of claim 3. wherein the motor drive is actively controlled to maintain a minimum motor winding temperature without overheating the motor winding.

5. A method of heating a motor winding of an electric motor, the method comprising: operating, by a motor drive, the motor winding of the electric motor as a heater to prevent condensation on the motor winding.

6. The method o f claim 5 , wherein the motor drive is configured to operate the motor winding as a heater when the electric motor is non-operatiomil or inactive.

7. The method of claim 5, comprising: controlling and monitoring a motor winding temperature to assure that the motor winding temperature is wanner than a dew point temperature of surrounding air,8. The method of claim 7, comprising: actively controlling the motor drive to maintain a minimum motor winding temperature without overheating the motor winding.

9. A non-transitory computer readable medium which stores instructions that, w'hen executed by a computer, perform a method, comprising: receiving motor winding temperature sensor data of an electric motor, controlling a motor winding temperature so that the motor winding temperature is wanner than a dew point temperature of surrounding air..

10. The medium of claim 9, utilized by a motor drive connected to the electric motor.