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Information Require About Dc Motor Working Temperature


AB2005

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Dear Friends.

 

We have a DC motor Leroy Somer brand LSK 1324 VL 49KW 2530RPM 185Nm at Flexo machine. The max current of motor is 126A and its normal running load is 75A. In these days when surrounding temperature remains 25-30C, the motor temperate remains up to 61C during normal running. Last month, a Japanese Mech Engineer visited to our plant and he stated that motor temperature >61C is not good. It must be < 60C. I tried to get the detail of motor acceptable temperature rise from Leroy Somer but they did not feed back. I could not get such info from its user manual. SO please help me out if this temperature of motor is normal? What is the acceptable temperature rise of this motor?

"Don't assume any thing, always check/ask and clear yourself".

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Dear Friends.

 

We have a DC motor Leroy Somer brand LSK 1324 VL 49KW 2530RPM 185Nm at Flexo machine. The max current of motor is 126A and its normal running load is 75A. In these days when surrounding temperature remains 25-30C, the motor temperate remains up to 61C during normal running. Last month, a Japanese Mech Engineer visited to our plant and he stated that motor temperature >61C is not good. It must be < 60C. I tried to get the detail of motor acceptable temperature rise from Leroy Somer but they did not feed back. I could not get such info from its user manual. SO please help me out if this temperature of motor is normal? What is the acceptable temperature rise of this motor?

 

 

AB2005 -

 

I have sent an inquiry to Leroy Somer on your behalf.

 

Q. Please Describe the method you used to determine motor temperature is 61 deg. C.

 

 

I am assuming that you are not located in the USA and that your motor conforms to IEC standards.

 

Advise if this is not correct.

 

I will further assume that because of the way the motor is installed, that it is not easy to observe the Rating Plate on the motor. If you are able to observe the rating plate on the motor, the Max. Ambient Temperature should be listed, the insulation class ( A or B or F or H) should also be listed ... and I would also expect that the rated Temperature Rise in deg. C. would also be listed on the rating plate.

 

Motor with

  • class A insulation are rated for a 60 deg. C. rise above a 40 deg. C. ambient
  • class B insulation are rated for an 80 deg. C. rise above a 40 deg. C. ambient
  • class F insulation are rated for a 105 deg. C. rise above a 40 deg. C. ambient

 

I will also assume that your motor has a wound shunt field coil in it. Shunt Field current will also contribute to motor temperature rise ... so it is important to MEASURE the Shunt Field Current and be certain that it does not exceed the value listed on the motor rating plate.

 

 

My past experience with DC Motors applied to Flexo applications is that they do run hot ... but do not exceed the design specification of motor.

 

Consider: a motor in a 40 deg. C. ambient with Class A insulation will have a 60 deg. C. rise above ambient ... That's about 100 deg. C. and you will not be able to hold you hand on that motor as it will cause your skin to burn.

 

In some locations where the ambient temperature is very high .... I have seen motors where the maintenance department has installed a fan to blow air on the motor in order to get additional cooling.

 

I will also assume that your particular motor does not have a blower mounted to it. It is therefore important to operate this machine at >60% speed to get cooling. Operation below this speed should be limited to short time duty—i.e., for set-up only....

 

Kind regards,

 

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Dear Friends.

 

We have a DC motor Leroy Somer brand LSK 1324 VL 49KW 2530RPM 185Nm at Flexo machine. The max current of motor is 126A and its normal running load is 75A. In these days when surrounding temperature remains 25-30C, the motor temperate remains up to 61C during normal running. Last month, a Japanese Mech Engineer visited to our plant and he stated that motor temperature >61C is not good. It must be < 60C. I tried to get the detail of motor acceptable temperature rise from Leroy Somer but they did not feed back. I could not get such info from its user manual. SO please help me out if this temperature of motor is normal? What is the acceptable temperature rise of this motor?

 

 

AB2005 --

 

Does this look like your motor ?

 

http://www.transdrive.co.uk/images/dcMotors/leroySomer.jpg

 

:: :: ::

 

According to the curve for the LSK 1324 motor (see: LSK Motors kW vs RPM family of curves) your motor should be good for around 63 kW @ 2530 rpm.......

 

It also has Class H insulation and should be good for a 180 deg. C. Rise over a 40 deg. C. ambient.

 

...

 

 

I am awaiting confirmation of these facts from Leroy Somer.... and expect that they will confirm. Which then makes me question advice that Japanese MECHANICAL engineer gave you .... I would say he is very wrong.

 

 

Kind regards,

 

 

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Thank you Jomega.

 

1) Exactly the same motor with cooling fan as you mentioned in picture but 49KW, not 63KW.

2) I measure the temp by a non-contact temperature gun.

3) Name plate is not easily accessible.

4) Yes I am not related with USA region.

 

 

 

 

"Don't assume any thing, always check/ask and clear yourself".

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Thank you Jomega.

 

1) Exactly the same motor with cooling fan as you mentioned in picture but 49KW, not 63KW.

2) I measure the temp by a non-contact temperature gun.

3) Name plate is not easily accessible.

4) Yes I am not related with USA region.

 

 

As of this morning, I'm still waiting for reply from Emerson/Leroy Somers/

 

 

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As of this morning, I'm still waiting for reply from Emerson/Leroy Somer.

 

 

AB2005

 

I now have confirmation of motor technical data from Emerson Industrial Automation / Leroy Somer;

 

Part Number:
LSK1324VL-11.49KW

 

Description:
LSK 1324 VL 11 . 49 kW at 2530 rpm . IMB3 (foot mounted - Horizontal)

Insulation Class H

Enclosure ODP BV - IP23S

Armature 440V / 126A

Field 360V

DT Tacho generator 60V 1000 rpm (1 collector)

I was also able to obtain a PDF file: LSK DC Motors 2 - 750 kW Technical Catalogue

  • This motor is rated to operate in a maximum ambient temperature of 40 deg. C.
  • Class H insulation is rated for 180 deg. C. rise above a 40 deg. C. ambient
  • MAX. Motor internal Hot Spot temperature of 220 deg. C. (180 + 40)
  • Motor has PTC thermal probes embedded inside motor. PTC leads (T1-T2) can be found in the motor terminal boxx.

 

If you suspect that there is a thermal problem, here are some suggestions for things to check:

  1. check blower for correct rotation. There is an Arrow on the blower that shows correct direction of rotation
  2. check filters at air intake of blower. When was last time they were cleaned ? Should be at least once/month.
  3. Check Air Discharge from motor. Should be strong air flow. and should not be obstructed. Discharge air must not be sucked into the blower inlet.
  4. Measure the ambient air temperature at the inlet (suction) of the blower. MUST be ≤ 40 deg. C.
  5. Check motor shunt field supply is according to specification. Nominal value is 360 volts. Technical Catalogue states that value between 320 and 380 is acceptable. Excessive motor field excitation will contribute to heat build-up in motor.

 

Hope this information is helpful to you. Let me know if I can be of further assistance to you.

 

If you would like a copy of the Technical Catalogue PDF file, send me an email at jomega@dridoc.com and I will send it to you as an attachment by return email.

 

Kind regards,

 

 

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  • This motor is rated to operate in a maximum ambient temperature of 40 deg. C.
  • Class H insulation is rated for 180 deg. C. rise above a 40 deg. C. ambient
  • MAX. Motor internal Hot Spot temperature of 220 deg. C. (180 + 40)
  • Motor has PTC thermal probes embedded inside motor. PTC leads (T1-T2) can be found in the motor terminal boxx.

 

If you suspect that there is a thermal problem, here are some suggestions for things to check:

  1. check blower for correct rotation. There is an Arrow on the blower that shows correct direction of rotation
  2. check filters at air intake of blower. When was last time they were cleaned ? Should be at least once/month.
  3. Check Air Discharge from motor. Should be strong air flow. and should not be obstructed. Discharge air must not be sucked into the blower inlet.
  4. Measure the ambient air temperature at the inlet (suction) of the blower. MUST be ≤ 40 deg. C.
  5. Check motor shunt field supply is according to specification. Nominal value is 360 volts. Technical Catalogue states that value between 320 and 380 is acceptable. Excessive motor field excitation will contribute to heat build-up in motor.

 

Thank you Jomega for working for me.

1) The direction of air flow of blower is OK.

2) We daily clean the filter and change it within one month.

3) Air inlet and discharge is OK. I have recently increased the area of air inlet by making some changes.

4) Ambient temp in these days is between 20-32C and max 48C in summer.

 

According to insulation class H properties, it means that during normal operation, motor body temp > 61C is no problem.

"Don't assume any thing, always check/ask and clear yourself".

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