Electronic Overcurrent Relay (EOCR) Settings

Thread Starter

cszikszai

Joined Nov 18, 2022
4
Hi,

To give you some background I am currently working on an Automated machine for Manufacturing that involves two air-blowers that are powered by 3-phase 208V power. The blowers are set-up in independent circuits with a Schneider 3DM2-WRDBWZ EOCR and 10A/20A MCB after the EOCR.

One of the EOCR's was incorrectly set-up and has resulted in a blown motor for one of the Air-Blowers. I have since replaced the blower, but I don't know what I settings I should use for the EOCR. The blower in question is a Leister Airpack rated for 3x 230V 50Hz and it is set-up in a 3-phase Delta configuration. According to the Blower Datasheet, the current pulled will be ~8.4A at 230V and be producing 2.2kW of power.

I am worried about blowing another motor, so I was wondering if anyone can direct me towards resources on how to set-up EOCR's to safely operate motors? What should I set for the Over-Current and Under-Current values?

I have tried to contact Schneider Support, but they said that the EOCR product is not supported in the US... And they did not refer me to any other support.

I have attached some supporting documentation. Any help would be much appreciated!

Thank you,
Chris Szikszai
 

Attachments

kaindub

Joined Oct 28, 2019
112
I used to work for Schneider and I have an extensive background in motors and protection.
Your motor looks to be a fairly standard squirrel cage motor. I would go with the default settings of the relay. The only thing you need to initially adjust is the current settng. Set it to the motor nameplate and youll be real close.
Dont worry about the undercurrent setting. It doesnt apply in a fan application. Same for overcurrent - it doesnt apply for a fan
 

Thread Starter

cszikszai

Joined Nov 18, 2022
4
I used to work for Schneider and I have an extensive background in motors and protection.
Your motor looks to be a fairly standard squirrel cage motor. I would go with the default settings of the relay. The only thing you need to initially adjust is the current settng. Set it to the motor nameplate and youll be real close.
Dont worry about the undercurrent setting. It doesnt apply in a fan application. Same for overcurrent - it doesnt apply for a fan
Hi Kaindub,

Thanks for the input! I set the EOCR within the the limits on name plate 8A +/-2A, but was getting undercurrent warning. I ended up setting it at 10A OC (overcurrent) and 3A UC (undercurrent).

The blower runs, but the line currents (measured from EOCR) are L1= 3.23A, L2=4.09A, and L3=3.54A. This seems a bit unbalanced to me, but I've also heard that all 3-phase motors naturally have some unbalance. I am also a bit confused on why the line currents are so low. I believe its underpowered because we're running the 230V rated motor with 208V, but shouldn't that cause an increased current?

Best,
Chris
 

kaindub

Joined Oct 28, 2019
112
Ok so there is your problem
The frequency of your supply as well as the voltage is important.
You should be running the motor nearer to 277V at 60Hz. You are running the motor significantly under voltage. Thats not good.
Yes you can set the motor relay up as per the nameplate, but the relay does not know you have a low voltage. The low voltage actually increases the heat in the motor which ends to it burning out. The relay will never detect this condition.
The motors are not suitable for your supply
The simplest solution , without changing out the motor, is to reconfigure the motor to a wye connection and run it of 480V three phase.
 

Thread Starter

cszikszai

Joined Nov 18, 2022
4
Ok so there is your problem
The frequency of your supply as well as the voltage is important.
You should be running the motor nearer to 277V at 60Hz. You are running the motor significantly under voltage. Thats not good.
Yes you can set the motor relay up as per the nameplate, but the relay does not know you have a low voltage. The low voltage actually increases the heat in the motor which ends to it burning out. The relay will never detect this condition.
The motors are not suitable for your supply
The simplest solution , without changing out the motor, is to reconfigure the motor to a wye connection and run it of 480V three phase.
Sounds good. Thank you for the time you took for the response! I will look into switching the wiring from delta to Wye configuration as well as double check the input frequency.

I think I was confused because the contractor that designed the machine directed us to wire it up to 210V 3-phase. They also claimed that they were using a converter to run the machine on their end at 110V line to line (delta config), which doesn’t make sense as that would equal 190V 3-phase input. I have a feeling that they were running the system at a higher input voltage during qualification.

Thanks again for the responses. I will do some more work on the system.
 
Top