375kw squirrel cage 415v motor starting issues

[Thomas_h]

Hey everyone thanks for reading.

We are having an issue with our cone crusher and starting. We have had engineers design the motor and starter know the full application and torque requirements of the cone crusher.

We are having intermittent starting issues. And have been for 2 years no one has been able to work out what is happening. We are using a soft starter and we change current limit settings. Does not matter if we increase it or then decrease it back to original settings it will then start. It will run and run and start then just not start. We change current limiting start up settings then it will start.

Bit of context on the site. A lot of electricians have been through and we have come to a common theory of it being a power quality issue. The whole site is run on diesel gensets and our power factor correction, due to lightning damage, is limited. We have our smallest filter and largest filter and we have a rectiformer that is always increasing and decreasing its draw and forever chasing the ideal power factor and at times crushing start up is an issue due to the sizes of our only 2 filters left that have to be manually controlled.

We get fitters to remove the guard and can spin freely and have removed belts and always starts up.

Can anyone shed some light on the effects of power quality with motor start up? The soft starter faults out on F4 - current limit start time expired.

 

[James]

Have you considered changing it to star - delta starting, it will not be affected much by power quality issues unlike the electronic soft start unit.

 

[Thomas_h]

Have you considered changing it to star - delta starting, it will not be affected much by power quality issues unlike the electronic

No we haven’t. The design has come the electrical and mechanical engineers who are contractors.

I don’t know a lot about star delta starting but I don’t think we’d have the torque requirements for starting it.

I have been on this site for 6 months and always having call outs to this particular motor and now all I did is slightly adjust the current limit on startup and it will then work. Operators think I’m a genius. Next time it won’t start I’ll adjust it back to what the engineer has specified and it works..

 

[James]

start-up torque should be about 1/3 of the rated motor torque in delta.