Too high current 2

[farale]

Hi everybody
No-load & full-load currents of a new motor are too high. What can be the reason?
Motor is: 7.5kW, 50Hz, 4 pole, full load current as per nameplate is 15A, but it is actually 24A. Measured no-load current is 10A. Motor is new. I have checked the terminal box and certainly the power cable is connected correctly.
What may be wrong?

 

[itsmoked]

Jeff; Fun chart, but dang if it isn't missing what we're talking about! Needs one more curve that shows UNLOADED AMPS with voltage.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

If that is a centrifugal fan, restrict the discharge of the fan with a baffle plate. Been there, done that, when someone miscalculated the back pressure of a large fan.
While this may look wasteful. it is not. When you get the FLA down to the nameplate value, the motor will be doing the rated amount of work; it will be delivering the same volume of air at the same back pressure as if the correct fan had been fitted.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

I don't get the +5 to -15 PF change with voltage.

I guess they're saying that a motor with say pf 0.9 at rated voltage might go from pf 0.95 at 85% voltage to pf 0.75 pf at 115% voltage.

As we increase voltage, the reactive current component associated with magnetizing branch of equivalent circuit increases (just like the no-load current increases) and the real current component decreases, so the reactive current becomes a larger portion of the total current and the power factor goes down.


=====================================
(2B)+(2B)' ?

 

[farale]

Thank you all for such great posts.
One thing to add: six leads of the stator wires are accessible. So it is possible to verify wirings (star / delta). It is connected in star mode. If I connect it in delta mode, certainly the current will increase.

 

[farale]

Here is motor datasheet, for further information.

 

[itsmoked]

Keith Cress
kcress -

http://www.flaminsystems.com

 

[John2025]

You're sure your supply is 50Hz, not 60HZ, right?

 

[FreddyNurk]

edison123, fair enough. I was thinking perhaps at that frame size it was a 380/660V motor.


EDMS Australia

 

[edison123]

The rated no-load current is already 50% of the load current, so 10 A at a higher voltage is not surprising.

What is surprising however is that such a detailed nameplate did not mention the motor connection anywhere.

Muthu

http://www.edison.co.in