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11 comments
Participant

Join Date: Apr 2010
Posts: 3

Three Phase Induction Motor

09/10/2010 3:57 PM

Dear Friends,

I'm facing a problem in a 3 phase induction motor used for a FERROMATIK MILACRON (SIGMA 110 TON) plastic injection moulding machine. The purpose is to move a variable pump to create hydrolic pressure. Now the problem is that the motor burned out within 2 days continuously after every new winding. The 20hp motor was showing 10-11 ampere at no load and 19-20 at full load. The motor heats up while running, also a burning smell is evident. I checked the bearing and it moves freely when I rotate the shaft manually. Can anyone give the reason behind it? please help me......

MOTOR RATING-MAKE BALDOR,1450 RPM,50HZ,NOM EFF 88.5%,20HP

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Guru
United States - Member - New Member

Join Date: Mar 2010
Location: In the pool because it is too hot.
Posts: 2740
Good Answers: 129
#1

Re: Three Phase Induction Motor

09/10/2010 11:43 PM

With this information multiple guesses are possible.

Too many to even start the book.

You are looking at a molding process, with product, temperature, volume, pressure and output parameters.

Your tools are the mold and the machine.

Something goes wrong in the process.

Is this a new setup? A new machine doing the maiden runs? A different mold? Other product? When you consider your productivity in weight, the easiest way is to check the balance between the needed HP at the speed of your motor. Is there an overpressure safety mechanism, or current limitation built in? What is the operating voltage? Is the current within the specs of the manufacturer? Bring it on.

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Power-User
Engineering Fields - Power Engineering - New Member

Join Date: Aug 2010
Posts: 106
Good Answers: 2
#2

Re: Three Phase Induction Motor

09/11/2010 1:00 AM

ill go with dvmdsc ambient temperatures need to be considered too...it may be that your motor it not suited for the environment it is operating..your frame size and service factor may be right but when it comes to you withstand temperature its another different story...

try looking at more details of your motor...it may be miss-looked..

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Anonymous Poster
#3

Re: Three Phase Induction Motor

09/11/2010 4:53 AM

Please check the connection of the motor, may be it is delta and you connected it star

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Participant

Join Date: Sep 2010
Posts: 4
#4

Re: Three Phase Induction Motor

09/11/2010 6:42 AM

What are the motor rated voltage and the rated current ?

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Anonymous Poster
#5

Re: Three Phase Induction Motor

09/11/2010 7:12 AM

Most probably the motor is slip ring induction motor with FLC of 27A.A DOL starter is used with interlock protections. check the protection schematic and verify the current rating is correctly adjusted. Adjust the timers as required.parallel operation of 2 motors simultaneously recommended. Hit

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Guru

Join Date: Dec 2007
Location: Mumbai, India
Posts: 1734
Good Answers: 23
#6

Re: Three Phase Induction Motor

09/11/2010 7:31 AM

Is there no protection to the motor?. Have you provided overload relay,HRC Fuses?.Is motor suitable for local voltage?.Is it supplied as OEM?.

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Active Contributor

Join Date: Apr 2008
Posts: 14
#7

Re: Three Phase Induction Motor

09/11/2010 7:37 AM

The motor windings are undersized for your operation which seems to have frequent motor starts and stops. Ensure that the rewinder uses a higher gauge wire and insulation is at class F. Your motor is already drawing 10HP at no load it would be important to check the shaft if wobbly as you have already certified the bearings to be okay. Finally you start system seems to be lacking thermal protection, if so it's imperative that you get an thermal overload relay rated at 23 amps or simply purchase a star delta starter c/w with overlaod relay with Ith 25 A.

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Guru

Join Date: Feb 2010
Posts: 1016
Good Answers: 36
#8

Re: Three Phase Induction Motor

09/11/2010 8:23 AM

Injection Moulding machine with the motor driving the hydraulic pump that actuates all the equipment mouvements. right?

This means that the motor is started and is running all the time, being loaded when the pressure is required by the different hydaulic motors and pistons... Therefore, the start/stop problem should not be relevant!(as indicated by some of the replies).

Now: If the maximum current taken by the motor is as you stated, 20A under loading conditions, and from the data you provided (voltage missing!?) is take it that the phase voltage = 400V and p.f. = 0.8, then the motor max nameplate current should be ~ 24 to 25 A, then you are within the specs for this motor. Being an intermittent loading / unloading, the motor should be able to withstand the current and the duty cycles imposed.

What remains are 3 things:

1- Check if the 3 phases are balanced (taking the same current when running on load and off load). If not, then you have a problem with the contactors &/Or cables supply etc. One phase might be taking too much current... But then the O/Load devices should trip the Motor and protect it (Unless they have been by-passed or set wrongly!).

2- Mechanical problems: Hydraulic pump getting jammed, not free running (this might be sporadic and intermittent ) and causing the motor to overheat. But this should have been obvious from other signs.(high current peaks...)

3- Bad Ventilation: Check that the cooling fan is in perfect condition and that it is properly secured to the motor's shaft (could be slipping arround!!). and that the area is not blocked for free mouvement of air. if need be, install an auxiliary blower to circulate the air within the motor's vicinity.

Apart from the above, there should be no reason for the motor to burn out after few days: this indicates that the motor winding is reasonably good but overheating! If the re-winding is made locally, check that the winder is using the correct wire gauge and INSULATION material: Re-winding wires are classified for different temperature increases etc. you probably need Insulation material of Class F. Check motor nameplate for Ins.Cl marking.

I hope it helps.

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Anonymous Poster
#9
In reply to #8

Re: Three Phase Induction Motor

09/11/2010 2:40 PM

thank u luke for helping me. i will check again according ur instructions. thank u vry much

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Anonymous Poster
#10

Re: Three Phase Induction Motor

09/12/2010 8:25 AM

Have you checked the rotor with MCA or ESA, a die caste rotor could have voids in the casting, a fabricated one could have broken bars / high resistance joints. For this size motor I would imagine that it is die caste

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Anonymous Poster
#11

Re: Three Phase Induction Motor

09/13/2010 11:04 AM

I would measure the current draw when the injection machine is at max pressure max speed in the injection phase. Note that operators may abuse the parameters and place such a demand that the motor fails.

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Users who posted comments:

Anonymous Poster (5); cool moody (1); dvmdsc (1); edison (1); LAA_Lucke (1); rockraiden (1); suresh sharma (1)

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