Surface Heaters for DC Motors

Hello Abid

You don't give your Motor Site location, Motor Voltage, Make/Model of Motor, nor the local weather conditions, and those are necessary to properly answer your question.

In general, it is best to contact the Motor Make directly, because they will have tested the Motor and can advise you of temperature/humidity limits for that Motor.

Bearing lubrication is also temperature dependent, and in this, once again, the Motor Maker has the best knowledge for their own product.

It is always important that Dewpoint never occurs inside the motor, or else the windings will become damaged.

Likewise, if Dewpoint occurs inside the Motor, and the resultant condensed water freezes, it becomes possible for ice to form between rotor and stator, with consequent damage if Motor start is attempted.

Does your Motor have a Nameplate? If so, contact the Makers.

Advise further, with

Kind Regards....

Thankyou for reply and suggestions.

Our site is situated in Taif, Saudi Arabia. The motor is ABB made 400V DC, seperately excited, reversible, used as drive for passenger ropeway.

In winter the tempearture goes as low as 10 Degrees Celcius with little humidity.

Meanwhile I will try to contact ABB for their recomendations.

Thanks again.

I use these types, havent had a problem yet

http://www.resistance-technology.co.uk/anticondensationheaterachn1.htm

I think what you referring as surface heaters normally known as space heater in Motor manufacturer's terminology.The heaters need to be on during the time the motor is not in use .This is applicable for Both AC and Dc motors.The function of these heaters is to keep the temp. just high enough to prevent moisture condensation.With the quality of varnishes and Insulation compounds available to day moisture absorption by winding is highly unlikely if the motor is shut down for a short duration.Howver it is a good practice to kep the heaters on when motor is not in use.You can interlock the controls so that heater is on when motor is off circuit and eliminate human error.

Greetings,

The motor space heaters are used to stop condensation from occurring inside the motor and subsequently causing motor winding damage (shorting and/or grounding)and motor component corrosion.

The theory is best served by maintaining a temperature that is higher than the ambient dew-point and below the temperature (class) rating of the motor winding insulation.

All motors have an insulation class (A, B, C, D, E, F etc.) that determines the maximum allowable operating temperature. (see the motor nameplate and/or manufacturer motor data sheet for class rating or contact the motor manufacturer)

Motor mechanical loading (cycling loads) will affect the heat-load of the motor and needs to taken into consideration.

The motor nameplate should have the allowable temperature rise stated on it to help you in determining where to set the space heater temperature.

This is extremely important when dealing with "totally-enclosed" motors as any moisture "trapped" inside the motor must be kept in-suspension so as to prevent the moisture from condensing on the motor component surfaces.

With open motors the idea works fairly well but is limited by the relative humidity and ambient temperature along with circulating air quality.

Suspended dirt/dust will affect the results dramatically.

It may be in your best interest to change the temperature settings during different seasons of the year in order to offset ambient conditions and meet the required results.

ABB should be more than willing to help you address the application for a minimum or no cost to you.

Hope this helps.

Good luck!