Soft starter

[Sidewinder]

Can I ask why a MFT on low ohms is not sufficient?
And it’s a V belt I haven’t gone down to stripping anything down yet as it seems to be working fine now. Just wanted to understand the theory to why it was happening.

An MFT is not designed to measure the resistance of inductances such as motors.
They are VERY limited in their applications.
It’s about the right tool for the job.

You have 2 fans driven by two V belts driven from one motor, powered by a single soft-start?

Selectivity is another thing that should be looked at secondarily.
However more information is needed to make suggestions on the fundamental design.

 

[Jc1996]

An MFT is not designed to measure the resistance of inductances such as motors.
They are VERY limited in their applications.
It’s about the right tool for the job.

You have 2 fans driven by two V belts driven from one motor, powered by a single soft-start?

Selectivity is another thing that should be looked at secondarily.
However more information is needed to make suggestions on the fundamental design.

Sorry if I have made this unclear I have 2 blowers each run by their individual soft start and motor. These are identical bits of kit. The blower is driven via V belt.

 

[poni]

Sorry if I have made this unclear I have 2 blowers each run by their individual soft start and motor. These are identical bits of kit. The blower is driven via V belt.

OK now we are getting somewhere,

that sounds like the motor
if you have two soft starts and two fans with the same motor and it trips, I would change the motor

forget what I said here for the time being
do both motor's trip or just one?
have you swapped the motors across the soft-starts?
are they on the same mcb?

 

[Jc1996]

OK now we are getting somewhere,

forget what I said here for the time being
do both motor's trip or just one?
have you swapped the motors across the soft-starts?
are they on the same mcb?

only one motor is causing a the tripping. I wanted to eliminate the soft start being the issue so I swapped motors across the soft starts and the one I had the issue with still did the same thing on the second soft start.

 

[runningpiglet]

No fault code no just takes out the main breaker.


I’m not sure I 100% sure if what you’re saying but the motor does not have to overcome the opposite rotational force no. I’m just extremely baffled it must be something mechanical if when I connected the motor into the standby starter it did the same thing. Thanks for your help guys, just can’t get my head round this as if the main breaker goes out after a few seconds it’s as though the motor is struggling. However would this make the soft start output lower voltages?

You say the faulty motor trips the main breaker. Can you describe that breaker, is it MCB or RCBO or what and what are its current ratings? Can you determine if the tripping is due to overload or current imbalance? Is the supply three phase or single? What is the motor power rating?

 

[awarner]

Ok so if the motors have been swapped it should be the motor. Worn bearings and incorrect belt tension can cause the problem especially if the fault is intermittent, not a trick question, do you know how to tension a belt correctly? Apart from that then there is an issue on the windings and need to test as mentioned earlier.