Why Siemens low voltage motor takin higher amps than rated FLA at certain speed ?

[munzir]

Why the Siemens low voltage motor takes higher amps than rated FLA between certain speed/rpm limit ?

3 phase , squirrel cage induction motor

thanks

 

[FvM]

Mechanical overload?
Wrong inverter f/V characteristic selected?

 

[danishdeshmuk]

mistakenly written in this post sorry

 

[munzir]

drive (inverter) is connected with it ......... for its controlling .......
and the drive trips showing the alarm drive overload or sometimes motor overload and hence the motor stops

 

[munzir]

whether the load is lesser or bigger ...... trips in the range of these speeds ......

the drive , its parameters & hence the machine having this drive & motor is new ...... so i don't think that wrong v/f characteristics selected ..........

what might be the possible solutions & causes ?

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when speed is set between the speeds 50 m/min to 95 m/min inside HMI , then if the machine runs between any of the speed ranging in this stated speed for about more than 1 minute or 2 minutes ..... then tripping

 

[FvM]

You gave effectively zero information about the drive, so nobody knows what "whether the load is lesser or bigger" actually means.

An unloaded motor will consume very low power and draw a motor current that's only a fraction of the rated current (presuming correct voltage settings and no winding shorts).

Without any essential information, mechanical overload is the most likely explanation. You may want to monitor motor torque or drive output power to see the drive load. Most VFDs can display it.

 

[munzir]

Can you mention me what information you required so i could provide you those ?

thanks very much though

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its Yaskawa's drive H 1000

capacity : 15 KW
rated FLA of motor : 31.8 Amps
input : 380 V ac to 400 Vac

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How can i monitor the motor torque & power ? Are you referring at the motor electrical power ?

very bundle of thanks

 

[munzir]

input supply's frequency : 50 Hz
No not the torque nor the power is displayed at the drive

input drive voltage : 380 Vac to 400 Vac

 

[munzir]

Ya sorry about the wrong info mistakenly .... it shows the torque percentage & output power ....

do you want me to check that output power & torque percentage between that particular speed limit or at all the possible speeds ???

 

[FvM]

In my view, the assumption of "trivial" mechanical overload still holds. You need to gather all informations that may allow to distinguish between different overcurrent causes.

 

[munzir]

what are those info ? would you name those ?

 

[FvM]

Referring to your previous reports:

whether the load is lesser or bigger ...... trips in the range of these speeds ......

if the machine runs between any of the speed ranging in this stated speed for about more than 1 minute or 2 minutes ..... then tripping

You didn't tell about the kind of load and machine type at all. But despite of respective details, I still wonder how you know that the overcurrent isn't caused by mechanical overload? Tripping after 1 to 2 min means usually, the motor current is in the dynamical overload range (e.g. 100 to 160% of rated current) which isn't maintained for extended times to protect motor and inverter.

The best test for motor health and correct inverter settings would be to run the motor without load and check the motor current. Don't know if it's possible by machine design.

 

[munzir]

the motor is connected to a gear chain system.

its a rotogravure printing machine