Motor burning

To get better reply, you need to provide more specifications like motors manufacturer, insulation class, are you using phase failure relays? what are the causes of motor burnt out? bearing failure? phase failure? overheated? any fluctuations in the system voltage? are you using power factor correction units? motor allignment is it O.K?

will revert to you then,

Motors are different makes

Over Load Relay having protection for single phasing also

class B

No bearing failure

reason for burning - we want know

As I said in reply #9 you have an aerodynamic problem, not mechanical or electrical.

Just start the fan with closed damper (if you have it; you have to have it anyway) and open this damper gradually. When you find you have proper air capacity CFM stop opening, and pay attention to motor heating.

I can give you my comprehensive answer if you give me the data mentioned in the reply #9

APCCo

More to the point which one of these motors is burning out - just one of them or all three of them.

Presumably the motors are not all burning out in the same installations so that rules out any electrical supply problem.

This only leaves common mode electrical problems relating to your choice of overloads settings and protection, together with possible underrating of the motors.

Mechanical problems such as incorrect alignment, excessive bearing loading, assuming you are not using foot mounted motors for vertical fan applications, are these belt driven?, pulleys subject to belt slip can travel along the shaft and increase motor temperature

Or wrong class of motor for application and environment

More information required - you know the whole storey - we don't.

Sir,

Please share more info,Type of boiler, burner type and manufacture, amp draw at start up, room temp (high and low). Are your boilers over sized and cycling alot or are they running steady state with minimal cycles?

Please send info to miketheboilerguy@aol.com

Thanks

Mike

Thiyagarajn,

shortly pls write down every single letter on the each of motor's nameplate to get better view to help.

Many places like this has excess induction loads. This leads to bad power factor, this leads to destructive circulating currents which leads to motor heating. The power company may also use this to overcharge you. Suggest you get a recording power factor meter and watch power factor for 1 week.

You need to get rms current readings while the motors are operating.

hi,

if the motoe was keep on burning.pls see what type of motor insulation wire is used and mearsure the resistence value in off condition (motor in cool stage).after several hours runnig after take a resistence value caluculate the value.for temprature formula pls refer eletrical machine book.if temprature is more .pls use f class insulation.

1.40 HP motor relay setting may be at 54amps (after changing relay) considering 0.8 power factor.

2.Fix the time setting more in the Timer for star connection and monitor the heat of motor or run continuosly at star position for testing.

3. Check the contactor idealy without motor.

4.It is purly due to transient fault between star and Delta

5.Find out the heat generation by increasing the load gradually and record it for identify the load current.

6.Give the Test date for next analysis.

I believe you are talking about the induced and forced draft fans.

Please, e-mail (apcco@verizon.net) graphs with fan curves indicating working points (CFM, Total Pressure, Motor HP and Fan mechanical efficiency) on the fans with burning motors.

I think your problem is in aerodynamics of the air system.

I have had these cases in my clients facilities.

APCCo

Since your motors are already protected with overload relays and it is expected that they are of correct setting and rating and functional.The motors are not provided with single phasing protection the cause of motor burning has to be due to single phasing . Check up the electrical system for loose contacts in Incoming bus or circuit breakers or cable lugs and terminations.Provide single phasing protection to all large motors.

Dear Mr. Abraham,

The overload relays are of L & T make and they have built in single phase protection.

Regards.

R.Thiyagarajn

Check if the air is with textile matter and rice husk jaming the bearing in the fan and so burning the motor. check if you check the qualit of air and to ensure the the bearings are not jammed which seems probable in atextile and rice mill boilers. Install some fileters so that air sucked is normally clean.

Dear sir,

Normally fan motors are continuous running.So it needs F class insulation. Another factor CFM.Kindly reduce rpm and install pneumatic damper.Motor service factor higher than unity.

SANKAR.