55 KW Siemens Motor Tripping

The problem is that the load presented to the motor at start-up is too large.

Is the blower a positive displacement one?

Normally blowers are centrifugal and fitted with some sort of guide vanes for capacity control. While starting these guide vanes should be in minimum position so that minimum quantity of air will enter for reasonable starting torque. Please check the condition and position of these vanes.

......and refer to the manufacturer's start-up procedures lest any part of them may have become inadvertently ignored.

Type of start?

Your rated FLA is about 100A (assuming 415V) so the NoLoad Current of 19A is about OK.

The FLA of 100A itself is beyond your relay range (40-57A)

Compounded to that the starting current for 100A FLA will be quite large (unless you go for a real specific soft start) and would be beyond the rating of the relay. I don't expect the 55KW motor to be at higher voltage of course.

Check the selection of motor and relay.

........and the sizing of the supply cables!

Dear Friends,

Thank you for the suggestions. we got it right by replacing the OLR of higher range.

Now the motor is not tripping and it takes 55 A on load. and runs smoothly with normal temp. on the motor

olr range use is 70 - 95 A.

Thanks a lot for all.

Most likely if you are using an OL relay that small on that size of motor, you are using Star-Delta starting.

First you should follow the advice of pritam and PWSlack with regards to investigating the conditions thoroughly. The issue of guide vanes is a big mistake often seen in centrifugal blower applications; people often think that if the guide vanes are wide open it is EASIER to start because there is no resistance to the flow, but in fact the EXACT OPPOSITE is true. Load in a centrifugal machine is directly proportional to FLOW. So the more flow is allowed, the higher the load on the motor. It's almost universal that a machine designer will select a motor's starting capability for the NO-FLOW condition of the blower, meaning the vanes are CLOSED. That is why, as PWSlack said, you should be thorough in your investigation of the blower mfrs starting and commissioning instructions.

If it is starting with the vanes closed, or it is not a centrifugal blower, then another possibility is that the Star-Delta timing is too long, which might be something you can adjust an correct, but it may also mean the motor is undersized for the application or that Star-Delta is an inappropriate starting method.

Lots of possibilities at this point, you need to investigate further if any help we give you is to be meaningful.

Good luck.

If the motor winding was aged there is a chance for such failure, It shows correct resistance with multimeter, but in practical application it may fail due to decrease in insulation resistance check the insulation resistance with megger Check the bearing condition of the motor. Check the direction of rotation of motor, It may have protection to avoid reverse rotation. check the cabling termination and supply voltage.

Probably you are using a Class 10 or Class 10A Overload Relay. Please replace it with a Class 30 Overload Relay.