Thread: VSD power tests

Aaron (azzrock) should be REALLY excited about this in relation to his Deckel mill! It has a two speed (4-pole and 8-pole) motor and buried star points...
Even I am excited for him

Hi Bob,

Guess who?

Could you add 100hz and 120 hz to the Star connected tests please. The graph it against the delta data.
While star connect means you'll never get to rated hp, it looks like the hp curve maybe flatter than in delta. Given I have a 3hp motor for a 2hp lathe, losing some hp if it flattens the curve is not a problem.

Thank you again

Stuart

Originally Posted by Stustoys

Hi Bob,

Guess who?

Could you add 100hz and 120 hz to the Star connected tests please.

At which BLF?

The graph it against the delta data.

Rodger.

I found some steel to make a bigger drum and have given it priority 5b so it could some time before it is ready but priorities have a habit of changing rapidly.

Originally Posted by BobL

At which BLF?

As I understand it, it wont make any difference. But as it has to be one or the other I pick 29Hz.

Thank you

Stuart

Hi Bob,

Excellent work, those stuck with star wound motors and missing star points will love those results..

I'm still keen to see some current indication on those graphs, ideally nameplate current, but really anything... it's essential to interpreting the data.

Ray

I had another look at the measured current data and realised I was plotting the wrong data for a couple of frequencies. Also I had remeasured the 60Hz frequency and the HP data for that now made more sense. The red line shows the HP at the calculated nameplate current for each frequency on the ∆ plot.

I'd ignore the dip in the contour at 55Hz.
I'll generate the same plot for the other curves WIGRTI

Hi Bob,



I've plotted an overlay with the theoretical performance of the motor, assuming it lives up to it's nameplate 1hp rating. I was half expecting prior to you starting the tests that the motor would probably have given out less than 1hp when running on a vfd at 50hz because of the voltage drop in the single to 3 phase conversion. Not so, you get in fact 10-15% more.. I'd say that the hp rating on that motor is conservative..

Ray

Ahhh, now if we could repeat that with a Sensorless Flux Vector VFD..... It should extend the useful speed ratio from 4:1 (for a simple V/Hz VFD) to at least 6:1 if not almost 8:1..... The difference would all be at the slow speeds, from near standstill to about 25Hz.

And then the same with a closed loop VFD, using an encoder feedback.

Unfortunately I have currently no spare vector VFD I could loan to you, and do not want to rip it out a machine.

Originally Posted by RayG

Hi Bob,
I've plotted an overlay with the theoretical performance of the motor, assuming it lives up to it's nameplate 1hp rating. I was half expecting prior to you starting the tests that the motor would probably have given out less than 1hp when running on a vfd at 50hz because of the voltage drop in the single to 3 phase conversion. Not so, you get in fact 10-15% more.. I'd say that the hp rating on that motor is conservative..
Ray

Some of the discrepancy may be explained by the following
I've been meaning to photograph and post the nameplate for some time.



The 3.6A appears to related to an input V of 220V.
I assume the output of the VFD tracks the input and looking at the input to the VFD during these tests it ranges from a low of 227V through to a high of 247V. Mostly it is in the high 230's and low 240s with an average of over 240V.

The variation in the Voltage may also explain the differences between repeated measurements

Originally Posted by BobL

Some of the discrepancy may be explained by the following
I've been meaning to photograph and post the nameplate for some time.

The 3.6A appears to related to an input V of 220V.

Thanks for that! That makes perfect sense, if you lift the 50Hz point to 1.1 hp, the experimental data fits nicely with the theory, plus or minus a bit of experimental scatter.

The line from 50Hz down to zero won't actually go through zero, because of the torque boost voltage.

Above 50hz you can calculate the drop in torque easily as well, going from 50hz to 100hz the torque will be half. t=5252*(hp/rpm)

Ray

Originally Posted by RayG

Thanks for that! That makes perfect sense, if you lift the 50Hz point to 1.1 hp, the experimental data fits nicely with the theory, plus or minus a bit of experimental scatter.

The line from 50Hz down to zero won't actually go through zero, because of the torque boost voltage.
Above 50hz you can calculate the drop in torque easily as well, going from 50hz to 100hz the torque will be half. t=5252*(hp/rpm)
Ray

Tis' a minor point but the 50Hz curve on my graph is one curve more left of the one where you start to plot the HP line.

Any suggestion as to what current to use for the 240V Y connection graph?

Originally Posted by BobL

Tis' a minor point but the 50Hz curve on my graph is one curve more left of the one where you start to plot the HP line.

Ok, I'll replot it and edit the earlier post to reflect the difference in hp between 220 and 240v

Originally Posted by BobL

Any suggestion as to what current to use for the 240V Y connection graph?

Yep.. 3.6 / 1.732 = 2.1

Originally Posted by BobL

Some of the discrepancy may be explained by the following
I've been meaning to photograph and post the nameplate for some time.



The 3.6A appears to related to an input V of 220V.
I assume the output of the VFD tracks the input and looking at the input to the VFD during these tests it ranges from a low of 227V through to a high of 247V. Mostly it is in the high 230's and low 240s with an average of over 240V.

The variation in the Voltage may also explain the differences between repeated measurements

This is the data sheet for your motor MK110019-2:
MT90S ... - Datasheet Search Engine Download

Looks like it is rated 0.75/0.9kW, 1410-1700rpm.

The motor has to deliver at least 1HP at its lowest rated frequency (50Hz) and its lowest rated voltage (220V). Hence it can deliver more than 1HP either at a higher voltage, or at a higher frequency, and even more at both the highest voltage of 240V and the highest frequency of 60Hz.

EDIT: the data sheet says clearly "...This wide voltage range and dual operating frequency enables the motors to be used throughout the world...."

EDIT: Look at table 4: it says clearly that the motor which is wound for 220V at at 50Hz, will deliver 1HP if connected to 60Hz and 220V, and 1.1HP if connected to 255V and 60Hz. The Australian power grid is officially 230V +15%-5%, so it can at times be as high as 264.5V... and this means a VFD can deliver up to that much at its output.

Hi Bob,

While I have not contributed or made comment (yet) on your thread, I wish to thank you for the work you have done. Up until now there has only been theory discussions on this subject and while I have no need or basis to disagree with any of it, being able to look at real data is fantastic!

Thankyou.

Simon