# 3 phase motor current



## BillyMac59 (Sep 12, 2019)

Yes


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## Wardenclyffe (Jan 11, 2019)

With a meter,...


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## Saedi (Nov 6, 2020)

Wardenclyffe said:


> With a meter,...


How? What is the process?


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## BillyMac59 (Sep 12, 2019)

First things first...are you an electrician?...I find it curious that you have been on this site for 2 years, your two posts here are your first ever and your only now trying to find out how to ring out a motor? At least tell us what you've tried so far. Telling you the answer will, among other things, rob your local electrician of a service call. If you think I'm being a harda** for these comments, you would be right! People on this site are happy to help BUT they won't do your work for you.


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## Saedi (Nov 6, 2020)

I hope not all Electrican like you, answer me if you don’t know let others do it don’t waste our time.
230v/3phase c/w FLA 8.5A


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## Dennis Alwon (May 9, 2009)

Use a clamp on amp meter around each phase conductor


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## BillyMac59 (Sep 12, 2019)

I'm sure a moderator will be along soon to address your concerns...you will have better luck on youtube or google....as far as what you infer may be an attitute, please be advised that I'm onbe of the easy-going likeable guys....if you're really wanting to see and read attitude, just continue on this path...


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## Dennis Alwon (May 9, 2009)

Thanks for posting on ElectricianTalk.com. However, working with electricity and electrical systems can be unsafe if not done by a professional licensed electrician. The moderators of this site would like to advise you to contact a professional electrician in your area. If you are permitted by law in your area to do your own electrical work, please sign up at our sister site, www.DIYChatroom.com where many of our professionals are also members and are looking forward to assist you with your needs. Please take a moment to post your question at www.DIYChatroom.com If you're not already a member of DIYChatroom.com you can sign up for a free account by going to Register We apologize for any inconvenience that this may have caused. This thread has been closed.


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## joe-nwt (Mar 28, 2019)

Saedi said:


> I hope not all Electrican like you, answer me if you don’t know let others do it don’t waste our time.
> 230v/3phase c/w FLA 8.5A


Maybe not all, but most.


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## Wardenclyffe (Jan 11, 2019)

Now what do the readings mean,...

IBTL


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## Saedi (Nov 6, 2020)

Dennis Alwon said:


> Thanks for posting on ElectricianTalk.com. However, working with electricity and electrical systems can be unsafe if not done by a professional licensed electrician. The moderators of this site would like to advise you to contact a professional electrician in your area. If you are permitted by law in your area to do your own electrical work, please sign up at our sister site, www.DIYChatroom.com where many of our professionals are also members and are looking forward to assist you with your needs. Please take a moment to post your question at www.DIYChatroom.com If you're not already a member of DIYChatroom.com you can sign up for a free account by going to Register We apologize for any inconvenience that this may have caused. This thread has been closed.


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## Saedi (Nov 6, 2020)

Guys
I am electrician licensed 309A
But I do the test for motor three phase 
I put clampmeter on each phase I got below:
5.2 A
5.4 A
5 A
On name plate FLA 8.5A
Is that mean the motor bad or VFD drive?


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## tmessner (Apr 1, 2013)

Saedi said:


> Guys
> I am electrician licensed 309A
> But I do the test for motor three phase
> I put clampmeter on each phase I got below:
> ...


I do not know how you passed a test or filled out your time requirements if you do not know the answers to your questions. Any first year apprentice should know how to do what you are asking and know what the results mean.


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## Saedi (Nov 6, 2020)

tmessner said:


> I do not know how you passed a test or filled out your time requirements if you do not know the answers to your questions. Any first year apprentice should know how to do what you are asking and know what the results mean.


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## Saedi (Nov 6, 2020)

Then answer if you know


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## tmessner (Apr 1, 2013)

What do you think it means if a motor is pulling less than full load?


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## Saedi (Nov 6, 2020)

tmessner said:


> What do you think it means if a motor is pulling less than full load?


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## Saedi (Nov 6, 2020)

Are you ask or answer?
Don’t talk regarding something


tmessner said:


> What do you think it means if a motor is pulling less than full load?


are you answer or asking?


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## Wardenclyffe (Jan 11, 2019)

Yeah, but what's the Service Factor,...


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## gpop (May 14, 2018)

when it comes to motor's amp's are a reaction to load. A motor will pull as many amps as required to match the magnet field so your motor will pull anything between 4-5 amps (no load) to 56 amps (rotor locked). 

Yours motor is rated at 8.5 x SF so 5.2ish means the motor is not under a heavy load when compared to its horse power.

As for the amp difference with out knowing the type of meter (if you centered the wire in the clamp) and the voltage as its on a vfd it looks close enough. 
Does that mean its a good motor ......nope it just means its a running motor that's not heavily loaded


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## tmessner (Apr 1, 2013)

Would please tell us a little about your background and what experience and training you have had?


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## Saedi (Nov 6, 2020)

gpop said:


> when it comes to motor's amp's are a reaction to load. A motor will pull as many amps as required to match the magnet field so your motor will pull anything between 4-5 amps (no load) to 56 amps (rotor locked).
> 
> Yours motor is rated at 8.5 x SF so 5.2ish means the motor is not under a heavy load when compared to its horse power.
> 
> ...


That’s what I want to know so I was thinking nothing wrong with motor that’s my attention to drive but I did the testing on the drive now and check the Parameters and software look the drive is okay too, I check it the motor with Megger for resistance & insulation test again nothing wrong with it.
Yes you’re right thanks for professional answer and hope everyone get knowledgeable with this post.


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## gpop (May 14, 2018)

Saedi said:


> That’s what I want to know so I was thinking nothing wrong with motor that’s my attention to drive but I did the testing on the drive now and check the Parameters and software look the drive is okay too, I check it the motor with Megger for resistance & insulation test again nothing wrong with it.
> Yes you’re right thanks for professional answer and hope everyone get knowledgeable with this post.



If you tell us what the problem is or what you are trying to accomplish we can probably point you in the right direction.


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## BillyMac59 (Sep 12, 2019)

I'll direct this to all readers....if this post was closed by a moderator (post #16) , how am I able to enter this comment?


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## gpop (May 14, 2018)

ValeoBill said:


> I'll direct this to all readers....if this post was closed by a moderator (post #16) , how am I able to enter this comment?



I presume he/she filled in his/her details so it got unlocked


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## JRaef (Mar 23, 2009)

Saedi said:


> Guys
> I am electrician licensed 309A
> But I do the test for motor three phase
> I put clampmeter on each phase I got below:
> ...


The current it based on the LOAD on the motor, so we have no idea if this is showing anything meaningful, but if it is not MORE than the FLA, then I wouldn't get excited about it.

The other issue is balance of the currents. Average the current, then look at the difference between average and the individuals. Anything more than 1% indicates a possible issue with the motor. But what you can do is to "roll" the connections to see if the imbalance follows. Rolling means that you reconnect it, in the same relative rotation, but move wires. So A goes to B, B goes to C, C goes to A. Then measure again and see if the imbalance follows or stays the same. If it follows, it's in the motor. If it stays the same, than it's in the source.


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## Navyguy (Mar 15, 2010)

Saedi said:


> Is that mean the motor bad or VFD drive?


One of my pet peeves... Like saying my SIN number, or my SSN number or raise up or lower down...

Cheers
John


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## paulengr (Oct 8, 2017)

Navyguy said:


> One of my pet peeves... Like saying my SIN number, or my SSN number or raise up or lower down...
> 
> Cheers
> John


You can’t tell from that. Based on just the numbers it looks like either a loose connection or a motor issue because of the current unbalance. But amp clamps are also notoriously inaccurate. A flexible current probe will give more accurate numbers. Also check voltage at the motor terminals. Average the reading. Take the largest difference between the three readings and the average and divide by the average and take it as a percentage. That’s how to calculate unbalance. Current unbalance should be under 5%. Every percent voltage unbalance causes a 6-8% current unbalance. And more importantly if you see both, the issue is upstream. If only one, it’s downstream. So if I see a voltage unbalance at the starter terminals but not at the disconnect, starter contacts are worn out or there is a loose connection.

With a VFD there are several things to look for. You can test the back diodes with a multimeter on diode mode with the motor disconnected. Just test between DC+ and L1 through L3 then the same to T1 to T3. Reverse the leads and repeat. Then switch to DC- across all 6 terminals in both directions. You should see 0.3 to 0.6 V in one direction and open in the other in a consistent pattern. Deviations indicate a blown back diode.

Check capacitance from DC- to DC+. You need two identical drives to check accurately but usually bad caps are very obvious.

With the drive powered up test DC voltage with both DC and AC settings on your meter (AC ripple). DC should match whatever the drive reports for DC bus voltage and should equal input input line to line voltage x 145% on a six pulse drive. AC ripple should not be more than a couple volts.

With the drive in V/Hz mode output voltage above 12 Hz should be equal to motor voltage as a percentage equal to frequency as a percentage. So if it is running at 30 Hz on a 460 V motor output should be 230 VAC. In vector mode you can’t do this test. If it’s not working drive is defective.

With a scope look at all 3 outputs. Should be even with crisp pulses, no missing ones. Measuring voltage at the motor terminals zoom in on a pulse. You will see reflected waves which is the peak amount of overshoot where it is ringing (oscillating). This should not exceed motor surge voltage. On most motors keep it under 1200 V. On inverter duty should not exceed around 1600 V. If it does add/replace dv/dt filter. Check all three phases.

With a scope check for shaft current. You can get a special carbon brush pickup for this but you can also use a welders chipping hammer on the brush end the same way. Test shaft to frame. Should be 1-2 V at most. Look for peak. I’ve done it with some multimeters on max/peak function but the scope is the most reliable way. If this is an issue insulate one bearing and add a shaft grounding brush. Helwig and Aegis are both manufacturers. If this doesn’t work look at using Cool Blue filters.

VFDs are complicated and so is the testing.


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## Corporate_Big_Shot (Sep 27, 2019)

Saedi said:


> Guys
> I am electrician *licensed 309A*
> But I do the test for motor three phase
> I put clampmeter on each phase I got below:
> ...


How did you pass the 309A exam and get a job?

Also, nobody should be answering your question here. Only licensed professionals should be troubleshooting your problem.


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## Saedi (Nov 6, 2020)

Corporate_Big_Shot said:


> How did you pass the 309A exam and get a job?
> 
> Also, nobody should be answering your question here. Only licensed professionals should be troubleshooting your problem.


If you answer me this question I know you are professional electrician 
Why is the softstater give me fault when starting the 3 phase motor 575V?!


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## micromind (Aug 11, 2007)

Saedi said:


> If you answer me this question I know you are professional electrician
> Why is the softstater give me fault when starting the 3 phase motor 575V?!


What kind of fault is it?

There are many different types of faults, no one can answer if we don't know what type of fault it is.


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## Saedi (Nov 6, 2020)

micromind said:


> What kind of fault is it?
> 
> There are many different types of faults, no one can answer if we don't know what type of fault it is.


If I know why I asked?!


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## gpop (May 14, 2018)

Earlier in this chat it was a VFD now its a Softstarter.

Saedi is your native language french?


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## Saedi (Nov 6, 2020)

Saedi said:


> If I know why I asked?!





gpop said:


> Earlier in this chat it was a VFD now its a Softstarter.
> 
> Saedi is your native language french?


As electrician 


gpop said:


> Earlier in this chat it was a VFD now its a Softstarter.
> 
> Saedi is your native language french?


as you know as electrician you have to be familiar with too many things is this right? 
If you know answer me or let other professionals do that


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## gpop (May 14, 2018)

I put the answer in google translate and converted it to klingon as you are struggling with english.

tangqa' targh tu'lu' 'e' wIchaw'


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## Saedi (Nov 6, 2020)

gpop said:


> I put the answer in google translate and converted it to klingon as you are struggling with english.
> 
> tangqa' targh tu'lu' 'e' wIchaw'


Are electrician or interpreter?! Answer or stay away don’t waste my time


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## BillyMac59 (Sep 12, 2019)

I just gotta jump back in here....It appears your credentials have been accepted as those of an electrician so as a member who tries to help where I can, here goes...You have a problem with determining whether a motor is bad or not. You've check continuity phase-phase and phase-ground; you've meggered it and all is well? Lets look at you VFD/softstarter...what is the error code? Have you sourced a manual? Who is the manufacturer? Have you contacted them? (It has been 5 days+ since you brought this to our forum) Is this a new install or was it running and then developed a problem?


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## Saedi (Nov 6, 2020)

paulengr said:


> You can’t tell from that. Based on just the numbers it looks like either a loose connection or a motor issue because of the current unbalance. But amp clamps are also notoriously inaccurate. A flexible current probe will give more accurate numbers. Also check voltage at the motor terminals. Average the reading. Take the largest difference between the three readings and the average and divide by the average and take it as a percentage. That’s how to calculate unbalance. Current unbalance should be under 5%. Every percent voltage unbalance causes a 6-8% current unbalance. And more importantly if you see both, the issue is upstream. If only one, it’s downstream. So if I see a voltage unbalance at the starter terminals but not at the disconnect, starter contacts are worn out or there is a loose connection.
> 
> With a VFD there are several things to look for. You can test the back diodes with a multimeter on diode mode with the motor disconnected. Just test between DC+ and L1 through L3 then the same to T1 to T3. Reverse the leads and repeat. Then switch to DC- across all 6 terminals in both directions. You should see 0.3 to 0.6 V in one direction and open in the other in a consistent pattern. Deviations indicate a blown back diode.
> 
> ...


Yes I found it the softstarter problem and I changed it and put all prameters and configuration and change the contactor because it failed with one phase and I follow the engineering specifications for it 
Finally get the proper voltage
Thanks


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## joe-nwt (Mar 28, 2019)

gpop said:


> I put the answer in google translate and converted it to klingon as you are struggling with english.
> 
> tangqa' targh tu'lu' 'e' wIchaw'



I was curious so I cut and pasted that into a klingon translator.

"There is a buffalo dog"


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## Corporate_Big_Shot (Sep 27, 2019)

Saedi said:


> If you answer me this question I know you are professional electrician
> Why is the softstater give me fault when starting the 3 phase motor 575V?!


even for an apprentice electrician, that is an easy answer

but if you don't know what you are doing, then don't do anything because that is how accidents happen


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