Hi all 

In my company i have an inverter 6ra2216-8dd20-0 with 2 phase input 400V and output field 340 V dc 5 A 

 Because the winding off the motor (stator) leading heats 

about 130 degree i want ask the following 

a.I measure the output (field) 340 V DC and the stator (0-80V dc) varies the voltage but measure and ac voltage with my multimeter is this normal ? or maybe is the reason that warms the winding 

b. The current off the stator starts of 4A (12Vdc) when working at low engine speeds and reaches 5.2 A at high 

The machine despite having we work at low speeds (4A) after half an hour the winding off the motor stator heats , is there any way to further cut down the current ? i ask because the inverter has some potensiometers front 

and c . In your opinion none off the above does not apply and simply blame the motor ?

Hello,

Basically 6RA2216-8dd20-0 is converter & not inverter.

a. What is the application? Could you please provide rated details like armature voltage, current, field voltage field current, type of feed back etc. In general at fixed set point, armature & field voltage should not vary. How much it varies? Is blower working correctly? Is the direction of air flow, volume & intake air temp correct? Please check this.

b. Needs nominal motor data to comment on your point. BTW field voltage is 340V DC & 5 A where as armature voltage 12 V DC 5 A. What type of motor is this? What is the application?

Have you checked for any loose connection in field & armature wiring?

How you measure 130 deg temp? If it is so & if you run the motor in same condition, either motor winding will fail or the lead termination would get burnt off.

Have you checked motor field resistance at terminals, armature resistance, DC motor field & armature insulation resistance values?

Please check above points & reply here.

hi Piscean at first thanks you for your answer 

a. As regards the application with or without load the winding off armature heat , the fan and the direction off air flow ,volume and intake air temperature are correct .

The values that i measured are 

between c2,d2 field winding (341-342Vdc varies),170VAc ,3.4Adc 

between C1,D1 armature winding 11.3-11.7 Vdc varies ,20Vac 1.2Adc 

The voltage values were measured with digital multimeter and the currrent with inductive clamping dc , compared to the first time i asked the current is differ and i dont know why 

(Question) Is better the above physical quantities measured with oscilloscope ? i ask because i have a simple passive probe voltage (with attenuator 10X )which can measure 300Vrms , can i use this probe to measure at least the most low voltage off armature winding  (selecting on the oscilloscope dc coupling ,so except dc signal voltage can pass and ac signal voltage) as in my case or that may damage the oscilloscope channel or dc converter ?

b. the motor data i ll give you as attachment file 

resistance off motor is 

between c2,d2  267ohm  field winding and between c1,d1   3.7ohm resistaNCE insulation between armature and field windind couldnt measured it 

All the connections in the field and armature winding are ok 

finnaly as regards the temperature there are two ptc thermistor in series and through them goes a signal 24Vdc to a digital input plc . When the winding armature heats the correspond ptc increase the resistance and the signal reduset at 8 v dc (condition from one to zero in plc input) so i have fault overtemperature in machine 

Furthermore i chech the temperature off armature winding with thermal camera and show me 125 - 130 degrees

Based on motor name plate data, DC motor field current is 0.930 A & in field weakening mode minimum field current is 0.570 A. As per your readings, field current is 3.4 A DC & field winding resistance value is 267 Ohm. This is problematic & seems that field winding is internal short. Needs to check. This is the main reason of temp rise inside motor & check the motor by dismantling thoroughly, otherwise this heat may damage motor armature winding also.

I would not suggest you to use oscilloscope to check armature or field voltage DC wave forms since its range is very low. Oscilloscope is useful to check & measure thyristor gate pulses, tacho output wave forms etc. etc.

In short, please check your DC motor immediately before it leads to affect motor armature. After motor repairs, while connecting to drive check the field current & voltage parameters as per motor name plate. 

HTH.

Thanks again for your direct response 

Just one last thing that i want to ask you because its not me yet solved the question is that the motor data writes maximum voltage field 310 V
 and i measure 342V dc furthermore i measure 170Vac is this normal ? (i ask again because i expected a dc converter to have only dc output and almost no or minimum ac voltage ) so because i have so much ac voltage maybe except motor has and converter problem ? 

Finally because you are expert could you to suggest me any particular instrument voltage and current to buy that can be measured with great accuracy the output off dc converters

Nikolaosst77

Just one last thing that i want to ask you because its not me yet solved the question is that the motor data writes maximum voltage field 310 V

and i measure 342V dc furthermore i measure 170Vac is this normal ? (i ask again because i expected a dc converter to have only dc output and almost no or minimum ac voltage ) so because i have so much ac voltage maybe except motor has and converter problem ?

Hello,

In DC motor, motor torque is proportional to field flux. Field flux are directly proportional to field current. So in DC drive, DC field current is set & monitored instead of field voltage i.e. at motor nominal filed resistance & field current, field voltage is maintained. 

In your case since field winding is inter turn short, resistance value dropped than nominal value. Drive tries to maintain it that is why field current is high ( that is why DC out put is 342 V DC). Heat generation in winding is directly proportional to square of the current. As such in your case temp rise is very high. (130 deg cent, rated field current is 0.93 Amp where as actual drawn is 3.4 A, almost 3.6 times more) 

Thanks for your kind words. But I am not the expert. I learned little bit by practical experience & in this forum via knowledge shared by forum expert member KSN.

In DC drive, you can measure the output with simple DMM, not necessary to have any advance measuring instrument, since its out put is pulsating in nature, not purely straight line, load nature is inductive in nature. If you want to measure it with oscilloscope, then use probe with high attenuator range like X20 etc etc or use oscilloscope of high range. 

HTH.

thank you once again for your very quick and useful answers

but after all of the answers you gave me ,i created two more questions 

a. From motor data understood how to calculate the correct voltage and mostly the field current i should have . but regarding voltage and current should have in the armature winding how can i calculate what is right ?

and finally 

because as i said in my previous answers the values i measured for the current had some deviations , for example as regards the field current that i measured using an inductive clamping dc instrument 

sometimes other than 3.4 A as i have said  show me and 1.1 A (Which this value is normal and according this value the winding fieldis is ok and motor is ok ) . For this reason because i dont know if it is affected by a magnetic field maby and get wrong measurements ,

Can i use a simple digital  multimeter in series with one winding at a time selecting region dc  to measure the current without risk damage the output off dc converter ? 

So be sure and send the motor for repair winding off field 

To know the armature voltage & current, you should have motor nameplate & power data.

The field resistance & current which you mentioned in your post is clear indication that motor field winding is faulty. You may be getting current rating 1.2 A when field winding is in cold state/condition. You get your motor repair first. Then check the field current with tong-tester (clamp meter). If your DMM range is adequate then you may connect DMM in series to measure field current. 

HTH.

New question published by Nikolaosst77 is split to a separate thread with the subject Can reduce the current to system without having a problem?.

Best regards
Jen_Moderator