Motors

Barry White · Apr 5, 2014

Had a problem with a new motor installed by the contractors who fitted the new line. it was constantly taking out the single phase invertor that controlled it. decided to test the motor which was wired in what looked like star at first glance. it seemed out of balance. upon checking the rating plate I noticed star.star,delta and taking a closer look at the terminals noted 9 wires to six terminals u v w and u1 v1 w1.
I had ordered a spare motor the previous week so opened it up and read the instructions carefully.
its a double star/delta motor (not seen one before) and to run on the 230v 3 phase from the invertor it required no links and just a connection to u v w.
removed links and motor was balanced connected up and its been fine.
so it seems it was connected up wrong from the start.
Have to admit I have not seen this type of motor before and since it was rated star star/delta 230/400 v I would have expected the links to be put on u1 v1 w1. It was just the testing and the fact it was a new motor i noticed the extra wires.
the motor was by sew.
anyone else come across these? and why the new configuration

Darkwood · Apr 5, 2014

6, 9 and 12 lead are common depending on internal winding arrangement ...

Check the link ..I assume your motor connections are something like this link shows if you pic your set up.
http://www.firstelectricmotor.com/motor_connections.htm

Barry White · Apr 5, 2014

thanks for the reply Darkwood
Y Y Δ is how it was marked up and its single speed (never heard of wye had to google it to confirm its Y commonly used in US we have a couple of motors from US so will check the plates)
looked at the link and it dont seem to fit in the 3 phase category but thanks for the link will save it as I may find other motors I need to identify.
will grab the motor from the shelf and post back more info I just wired it as per instructions but want to understand how its actually wired inside and then why found this on google seems to be about powersaving but theres no control gear just a standard inverter for speed control

http://facta.junis.ni.ac.rs/eae/fu2k61/kostic.pdf

brian.507679 · Nov 4, 2014

How do you calculate a 3 phase motor. For a motor starter. Do you calculate each leg of the drawing amps

Knobhead · Nov 4, 2014

For a motor starter how do you think it’s calculated?

There’s two main ways one is theoretical the other is practical.

brian.507679 · Nov 4, 2014

Calculating each leg of your drawing amps and getting the total

Knobhead · Nov 5, 2014

How about looking at the motor rating plate? It will take average efficiency and power factor in to account so you don’t have to calculate it. You then simply set the O/L’s to match the motor.

Show some of the calculations you have done then I’ll go in to it in greater depth.

brian.507679 · Nov 5, 2014

The motor rating plate says 37 amps. The motor starter was set on 35 amps. When I checked the three wires that is going to the motor. Each leg was 14amps while running the motor

brian.507679 · Nov 5, 2014

My question is do I add the 3 legs that have 14 amps that is going across for my final adjustment

davesparks · Nov 5, 2014

Is there a problem with it at the moment?

It is obviously starting ok with the overload set at 35A otherwise you couldn't have measured the current.

brian.507679 · Nov 5, 2014

No not now I have adjusted it. Something was restricting the motor.

Darkwood · Nov 5, 2014

Can you take a photo of the plate on the motor and upload it, no offense but these plates are often misread, when you say motor starter, can you confirm the starting method - there are various methods for starting motors, also what was the setting before you adjusted it?

Something sounds amiss if you clamp it at 14amps and its been tripping prior you have set it to 35amps now, most manual overload settings dont span the range from 20amps to 35amps so are we talking been controlled by a VSD (DRIVE).

What is the duty of the motor - what kind of job is it doing?

You also say the motor starter WAS set on 35amps... what is it now? .... this isn't far off its optimum setting and shouldn't be altered unless you know what you are doing and why you have had to alter it.

Lastly, when exactly was it tripping.. and what was tripping, was it tripping on start up or while running, the Overloads should be compensated for start up currents and allow them unless you have some sort of high inertia load with a extended start up requirement, this will need another means of starting.