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Post by Catavolt » Thu, 09 Sep 2010, 18:07

The motor and drive I had the problem with was In the ultralight EV,
The carrier Freq was pretty low(2003) and the problem was at low rpm untill we grounded the rotor.
The problem wasnt helped by the fact we had to have the frame floating , Battery neg coudnt be grounded in the rules of the race.



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Post by acmotor » Fri, 10 Sep 2010, 04:30

Floating battery packs aren't as safe or logical as some folk make them out to be. Insulation suffers the uncertainty. "rules" on this topic are often out of fear and poor electrical practice in the first place. But don't start me on that topic. Image
Catavolt, what was the lateral and axial bearing load in the ultralight ?
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Post by Richo » Fri, 10 Sep 2010, 04:35

You can also note that most series DC motors have H class insulation.
If you are having an AC motor rewound for a lower voltage you can ask them to use H class wire.
There is not much of a price difference so I think it is worth asking for.
As for the bearing failure due to electrical imbalance you can also opt for the ceramic bearings.
Once again they cost extra.
But as others point out it is a minor issue these days.
I would probably recommend it on the first motor rebuild after you have been using it in your eV.
Considering you'd be up for less than $1000 for a full rebuild I would expect this to be less than an ICE rebuild - and less often...
So the short answer is NO but the long answer is YES.
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Post by Catavolt » Fri, 10 Sep 2010, 14:51

acmotor wrote:
Catavolt, what was the lateral and axial bearing load in the ultralight ?


Bushranger II had a Polly V belt apox 30mm wide with a 5:1 ratio and mild tension.
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Post by BigMouse » Wed, 10 Nov 2010, 04:37

Along the lines of this thread, I am curious about something regarding overvolting.

Assuming a 240v 50Hz motor, V/Hz = 240/50 = 4.8, correct?

If I understand correctly, in order to maintain rated torque at 100hz, 480v would be required from the VFD. I assume that the V/Hz ratio is maintained (disregarding boost) all the way from 0-100hz, meaning at 50hz, the voltage would still be 240v. Is that correct?

Is overvolting at higher frequencies common practice in industrial applications? Do industrial VFD's have this ability? I would expect most would be programmed to provide 100% of available voltage (100% PWM) at the base frequency. A 2x overvolt/overfreq installation would require 50% PWM at the base frequency.

Am I understanding this correctly?

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Post by coulomb » Wed, 10 Nov 2010, 04:59

BigMouse wrote: Assuming a 240v 50Hz motor, V/Hz = 240/50 = 4.8, correct?
Yes. But remember that 240 V 3 phase is unusual.
If I understand correctly, in order to maintain rated torque at 100hz, 480v would be required from the VFD. I assume that the V/Hz ratio is maintained (disregarding boost) all the way from 0-100hz, meaning at 50hz, the voltage would still be 240v. Is that correct?
Yes.

But it's more common to reconfigure the motor for lower voltage, so giving the motor all that the VFD is capable of is now overvoltaging it. So in your example, we'd rewire or rewind the motor to be 120 V, 50 Hz, i.e. it now has a V/Hz constant of 120/50 = 2.4.

It draws twice the current at 120 V, so the same power as it did at 240 V. But now, if we wind the VFD up to full voltage (240 V in this example), we have twice the rated power. The motor is likely to be able to put out this power almost continuously. So we've almost doubled the continuous rating of the controller by reconfiguring the wiring.
Is overvolting at higher frequencies common practice in industrial applications?
As far as I know, no. Industry just seems to use VFDs as a way of lowering the speed of a motor, compared to connecting it Direct On Line (DOL).
Do industrial VFD's have this ability?
If you mean the ability to output twice the nominal voltage, certainly not. The switches inside the VFD can reduce the voltage, but not increase it.
I would expect most would be programmed to provide 100% of available voltage (100% PWM) at the base frequency. A 2x overvolt/overfreq installation would require 50% PWM at the base frequency.
Yes, that's right. In my example above, the VFD would use 50% PWM to cut the 240 V down to 120 V, to get rated torque and power to the motor. It could then increase the frequency and voltage to a maximum of 100 Hz and 240 V (~100% PWM) to get about twice the power. (Not quite twice, since the windage losses will be higher at trice the speed, and iron losses will be higher at the higher frequency).

The VFD could also increase the speed beyond 100 Hz, leaving the voltage at 240 V. That would spin the motor faster, but the torque would be less than rated. This is the start of the so-called "constant power" region, where motor power decreases slowly with frequency. There may be another region (constant slip?) where the power will reduce quickly with frequency.
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Post by Richo » Thu, 11 Nov 2010, 05:09

BigMouse wrote: Assuming a 240v 50Hz motor, V/Hz = 240/50 = 4.8, correct?
coulomb wrote: Yes. But remember that 240 V 3 phase is unusual.
True except in sub 3kW inverter/motor combo's.
Most 3-phase motors 3kW and under are 240V delta.
So an el-cheapo VFD outputs 240V 3-phase for those motors.

So if you got a 3kW motor at 240V/50Hz which is common.
The V/F ratio is 4.8.
Now running it on a 415Vac VFD will give a power increase of 1.73.
Or will be 5.19kW 415Vac 86.5Hz (2500RPM for 4-pole)

And short term peak power of 15-18kW at 2500RPM.

Which for a motorbike is a bit on the low side.
And way too small even for a micro car.
Would make a great postie bike!

If you look at most cars the petrol engine develops peak power say around 4500RPM.
For a 3-phase 4-pole motor to produce peak power at 4500RPM it would need a voltage increase of 4500/1500=3.
So running 415Vac you would need the motor wound to 415/3=138Vac.
Now that 3kW motor with a power increase of 3 gives 9kW@415Vac@4500RPM.
And short term peak power of about 30kW at 4500RPM.
This is similar to a 250cc motorbike or a micro-car.


So the short answer is NO but the long answer is YES.
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Post by coulomb » Thu, 11 Nov 2010, 05:24

Richo wrote: True except in sub 3kW inverter/motor combo's.
Most 3-phase motors 3kW and under are 240V delta.
So an el-cheapo VFD outputs 240V 3-phase for those motors.
Oh, presumably from single phase input, on a ~ 16 A circuit?

So 240 VAC 1Φ -> 340 VDC -> almost 240 V 3Φ.

I didn't know that (I've never looked at the small stuff). Neat; thanks.
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Post by acmotor » Thu, 11 Nov 2010, 07:02

Do keep in mind that Oz is officially 230VAC single phase and 400VAC 3 phase. (240VAC and 415VAC went by the board 10 years ago ? though technically still within tollerance)

200 to 240V 3 phase is used in most of Canada, USA and Japan. Nearly all motors and VFDs are available in either voltage range.

Most VFDs use modified form factor to increase the RMS value of the H bridge output so output voltage can equal (or exceed slightly) input supply voltage (be it single or 3 phase).

One VFD I have (PDL) accepts 200VAC single or 3 phase through to 460VAC 3 phase. Current out is constant so max power varies WRT supply voltage.
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Post by Richo » Thu, 11 Nov 2010, 07:42

Yes - 230/400 I shouldn't use the old school voltages Image

The 3kW motor is assuming you are using the rated torque.
In my case I didn't need that much so I acutally had a smaller inverter.
It's just what I had laying around.
So the VFD would go into constant power a bit early.
Overall I was using less than 2kW so just had it plugged into a normal power point.

But if you were expecting to run a 3kW motor around it's cont rating then 16A circuit would be the go!
So the short answer is NO but the long answer is YES.
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Post by 7circle » Thu, 11 Nov 2010, 08:13

acmotor wrote: ...One VFD I have (PDL) accepts 200VAC single or 3 phase through to 460VAC 3 phase. Current out is constant so max power varies WRT supply voltage.


Does the VFD use Neutral for 460VAC line-line ?

Also do most VFD's have SCR-Diode bridges on the front end.

Would be nice if the SCR's could be used for battery series-parallel modes.
-Would need VFD to go no load and use SCR current reversal to turn off.
- Sorry another topic..

Are "Spindle" motors more suited to the higher RPM's and lower efficiencies?

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Post by Johny » Thu, 11 Nov 2010, 15:20

7circle wrote:Does the VFD use Neutral for 460VAC line-line ?
VFD don't use Neutral.
7circle wrote:Also do most VFD's have SCR-Diode bridges on the front end.
Lenze doesn't. They use large resistors that get bypassed with relay banks when DC voltage rises above about 400 VDC. Danfoss does use SCRs. Others???
Would be nice if the SCR's could be used for battery series-parallel modes.
-Would need VFD to go no load and use SCR current reversal to turn off.
- Sorry another topic.
Too hard to commutate, besides why switch battery modes - no advantage (that I can see). Switching the motor star/delta on the other hand has merit (although I haven't bothered after all).

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Post by acmotor » Thu, 11 Nov 2010, 17:14

Correct, VFDs generally have no neutral connection and single phase is just applied across 2 of the line inputs. (these two are often nominated as they can use higher current diodes or are monitored by the brain to know what is going on).
200VAC single phase gives some 280VDC on the bus and 460VAC gives 644VDC. The VFD works with what it has.
Actually, the VFD can work with anything over say 50V, its just a big switch, but the brain says no. Typically at around 470VDC for Oz models. "Normal" operation cannot be assured otherwise.

SCR's have their place, but not where the voltage drop across them when on (a few volts) or their need to be commutated off, outweighs their convenience. Phase angle (or half pulse) control of AC mains is their strong point. Contactors are still the best for battery switching. Even mosfets have a significant voltage drop under load (a volt or more), in fact on par with IGBTs above 100-200V.
Early VFDs were commutated SCR output. Pre ~1995 ?

It seems that generally VFDs above about 30kW use SCR high side input bridges from the mains. Purely to control inrush current on startup.
I can run a 450kW controller off a 20A 3 phase mains outlet and apply full motor current (1400A) at low RPM. i.e. low kW.

For EV applicaions the input side of the VFD is not important, as long as you have a method of controlling inrush if the VFD only had SCR input to control inrush.

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Post by 7circle » Fri, 12 Nov 2010, 07:37

(Sorry got carried away.... )
I noticed the "Altivar Telemecanique ATV58HD54N4" Sparky B has with his Feroza has the SCR's and its a 54HP rating. And was wondering if they had a useful purpose with battery setup. No point sacrificing efficiency just to use them.

With pulsed SCR operation to keep the DC bus caps above 400V would only loose the 1V drop when conducting current into the DC Bus Capacitor.
I realise too that pulsing current is also wasting energy in the circuit losses especially battery internal resistance.

Need to keep the RMS current as low as possible.
These thoughts come and get crossed off very quickly.

I thought the Brake IGBT could also be wired in to step up the Battery voltage.
But the IGBT needs much higher amp rating to say quadruple the voltage from 200 to 800V. And an inductor too. And then you need to make it bi-directional with another IBGT/Block.
Similar to Prius step up. But I realise their are other topics for this.

But to make the most out of the $ Value of the Capacitor bank and the IGBT block, would it be best to work close to their max rating.
As the switching losses are from transitions and ON/condution time. A higher DC bus will mean it is OFF more. So if less heat is made at the same current then the output bridge Current rating can be increased.

Just wondering about instead of relying on Battery Max Voltage as the DC Bus max of say 4.0V per Lithium cell. But operating at the Max instead of only 3.2V/cell under load would allow a 25% increase in DC bus Power capacity. So instead of operating at 640Vdc you operate at 800Vdc.
And then you have the benefit when the cells are at 30% to 20% SOC near 2.5V/Cell, the DC bus is only at 500Vdc. So Max speed would be limited if you need to finish your journey at highway speeds of 100km/h which needed 600Vdc Bus voltage.

So if the Inverter can achieve 95% efficiency with 800vdc and 8kHz at 60kM/h, the 100% rated Speed (60Hz looks convenient). But can get to 300% rated speed giving 180km/h, with 800Vdc but lower efficiency and 10% of Current. (...in a vacuum [:8)]
So for the Max Speed or Motor back emf at 300% is 550Vac, giving peak of 780Vdc.
Then at 100% rated BEMF is 183Vac and needs 435Aac-rms for 80kW.
So the avg PWM duty is based on current requirement into the motor impedance and BEMF.
(avg PWM because it is varying to give Sinusoidal output)

So at 60km/h and Full load, the 5% loss is made up of 60% transition (Rise/fall) and 40% is conduction losses.
With the 80kW output, 5% loss is 4.2kW, so 1.68kW is conduction Losses.
The 60% transition loss is 2.52kW

Maybe someone might have a real range of values for this.
There is probably a good explanation of this somewhere on the web.
Just trying to get to result for benefits of operating at a higher DC Bus Voltage.

So when the DC Bus is dropped from 800Vdc to 640Vdc the average PWM ON time would increase by about 25% for the same Current requirement.
The transition is lossy, but it still allows 1/2 power transfer to the motor.
So of the 2.52kW is passing to the motor during the transitions at 435 Aac RMS.
(The avg PWM with 16,000 transitions per second gives 2.53kW)

As the motor is at 60Hz with BEMF of 183Vac and current at 435Aac.
With the DC bus at 800Vdc the Base PWM is at 1/3rd. (33.3%)
So with DC bus at 640Vdc the PWM needs to increase by 25% to 41.25%

So the conduction losses increase by 25% from 1.68kW to 2.1kW.
This will make the IGBT a lot hotter.

With no canges to liquid cooling, then the losses would need to be kept at say 5kW.
The 60km/h loss at 640Vdc is now 2.1kW + 2.52kW = 4.72kW

When at over speed of 167% or 100Km/h and to keep the same loss at 5kW for Temp limit of IGBT the power output will need to de-rated for continuos.
There is some cooling benifit for the extra airflow at higher speed.

From 1.68kW(60km/h) to 2.80kW (100km/h) for 800Vdc
and for 640Vdc it is 25% more 3.5kW (100km/h)
- For same current 435Aac, this gives 2.8kW + 2.52kW = 5.32kW. at 800Vdc
- For same current 435Aac, this gives 3.5kW + 2.52kW = 6.02kW. at 640Vdc

For 800Vdc To pull back to 5kW needs 6% less current throughput.
So the 435Aac is reduced to 410Aac and so torque is reduced a little.
The Power output (183Vac x 166.7%) x (435Aac x 94%) = 124kW (+5.32kW = 129.32kW Pin)

For 640Vdc To pull back to 5kW needs 16.6% less current throughput.
So the 435Aac is reduced to 362Aac and so torque is reduced.
The Power output (183Vac x 166.7%) x (435Aac x 83.3%) = 110kW (+6.02kW = 116kW Pin)

So the drop from 800Vdc to 640Vdc (-20%)
gives power out put de-rating of 110kW from 124kW (-11.2%)
Drive Power in changes from 129.32kW to 116kW for 640Vdc

This is based on my dodgey numbers of 60% transition and 40% conduction loss at 80kW at 60Hz with 300% capability of 180Hz using 800Vdc Bus.

IGBT Vdrop is nonliner to current, but MOSFET Vdrop is Ron dependent so lower PWM duty lowers ratio but also Ron x Irms^2 is less too. So effect would be less on MOSFET bridge.

By using a 125kW bi-directional DC/DC with 800Vdc 125kW Output Bridge.
The a 180V (3.2V/cell) battery pack would be at 833A for 150kW.
Cost not cheap. But could be part of a 3phase 125KW Charger.
Would need a Primary/Secondary transformer.

LiFePO4 discharge curve is very flat compared to LiMn Ion and Lead-Acid.
So not sure if the benifits are justified for the cost.
Just thought it was worth posting after writing it out.

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Post by 7circle » Fri, 12 Nov 2010, 08:09

7circle wrote:
acmotor wrote: ...One VFD I have (PDL) accepts 200VAC single or 3 phase through to 460VAC 3 phase. Current out is constant so max power varies WRT supply voltage.


Does the VFD use Neutral for 460VAC line-line ?

Also do most VFD's have SCR-Diode bridges on the front end.

Would be nice if the SCR's could be used for battery series-parallel modes.
-Would need VFD to go no load and use SCR current reversal to turn off.
- Sorry another topic..

Are "Spindle" motors more suited to the higher RPM's and lower efficiencies?


Sorry the Neutral comments is silly because you want to keep any possible fault currents away from the Neutral.

But Are "Spindle" Motors as listed in some secondhand suppliers tables worth considering.

They are more expensive so was wondering why.
Spindle Motors Listed

Image
Image

With Max Voltage of 200Vac and a Current of 67A (30 minute)

How do they get 6000 RPM ot of these things with just 200Vac.

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Post by Electrocycle » Fri, 12 Nov 2010, 12:38

more Hertz :)

torque will of course drop off, so you don't get any more power - but they can run at high rpm for milling, etc.
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Post by Johny » Fri, 12 Nov 2010, 14:19

Aren't Spindle Motors an older name for Servo Motors or Synchronous AC Motors? All require an encoder input on the VFD otherwise they should be fine for EV work.

Edit: for NOT to
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Post by 7circle » Fri, 12 Nov 2010, 17:44

Some of the "Servo" motors on that site have "Permanant Magnet" on the name plate.

The 1500 RPM speed does suggest no slip at 50Hz for 4pole.

If its permanent magnet then the BACK emf is a lot more fixed as Kv Constant.
(Without fiddling with DC injection)

Then if at 6000 RPM the No-Load Bemf is 200Vac.
So at 1500 RPM the No-Load Motor Voltage is 1/4 of 200 or 50Vac

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Post by acmotor » Sat, 13 Nov 2010, 17:41

Or,
just thinking out loud....
ignoring pf...
11kW 1500RPM 62A suggests 11,000/62/1.73 = 102VAC
7.5kW 6000RPM 46A suggests 7500/46/1.73 = 94VAC
edit: so probably a 100VAC motor ?

The 200V number is just an insulation / magnetic saturation design limit ?

Interesting motor. What is the max torque ?

Easy check for PM motor... short the terminals and the motor shaft should appear almost locked to hand turn. Image
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Post by 7circle » Sun, 14 Nov 2010, 20:09

I came a across them on a second hand site.
SPINDLE MOTERS http://www.redrive.net/c=SRGpnmQQVj6JNR ... ry/motors/
So I was wondering what efficiency and power to weight they had.
They could also be reluctance motors.

Not sure how the Name Plate data works.
I don't think the RPM Nom and Max are linked to the 30min/Cont Current and Power.

So the torque at 1500RPM would be T=P/w (W:rad/sec)
7.5kW /(1500 x 3.1412/30) = 47Nm
11kW /(1500 x 2Pi/60)    = 70Nm

So if the controller kept the same current upto

This pdf has motor and controller info to build a system with sections on Motor Specs.

Here is "SERVO MOTOR" an old 1984 model on ebay for $800 Still a bit pricey for 15kW Cont at 1500RPM,
* * * * Our Internal # 3-D7-1 * * (10-12-10 dale) * * You are buying the following item: 1 - Model 15 FANUC AC SPINDLE DRIVE MOTOR, * * FLANGE MOUNT, * * Type# A06B-1015-B100, * * Serial No. # C-440016, * * Date: 84.1, * * 200 Volts, * * 1500/4500 RPM, * * Rating Cont. / 30 Min. - 15 / 18.5 KW, * * Amp Cont. / 30 Min. - 60/70 A, * * 4 Poles, * * Ins. Class F, * * 3 Ph., * * Amb. temp. 40 degree C., ..... blah blah about $$$ tatransport ...
Image

Needs a bit of TLC to clean it up. Just hunting quickly on ebay to see what spindle motors are around at lower prices.

Power to Weight is hard without knowing exact torques and current.
But wondering if they have a better efficiency characteristic.
Probably not.

A Fanuc Spinle Motor that ways 42kg with Pk Torque 30min of 215Nm has Power to Weight of 1600W/kg at rated 3000RPM would be 62KW for 30 min.

4 of these would be nice. But still trying to get balanceed idea to Induction Motors. Still not clear.


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Post by acmotor » Mon, 15 Nov 2010, 04:49

Servo motors can be an interesting option since they often contain an encoder and a brake (use for park brake). Their high initial cost (at least when new) and their priority on low rotor inertia rather than efficiency can be negatives. I guess look into any offerings on the market as they are quite suitable for EV drive. Image

Just for comparison, my old 11kW 4 pole 80kg 3PIM rewound for 100V has potentially 132kW for 1 min at 6000RPM (not 30min !). That is 132,000/80 = 1650W/kg so similar territory if the Fanuc is actually 215Nm at 3000RPM. Perhaps the Fanuc can go to 6000RPM and get 124kW ??? that would be useful.
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Post by 7circle » Mon, 15 Nov 2010, 08:14

The Fanuc Alpha "α50/3000HVis with fan" has 215Nm Peak torque and is only 42kg.

Problem is most specs are for the motor and controller as a combo for robotics.

So if you get a beefier controller and monitor the temp.

These style of motor look more like the MESdEA's.

But they doo cost a bundle.

Some have heavy rotors using low gaus Iron Magnets and others use NeoBlahBlahBased magnet making them react faster, like you said.

Then the High temps can damage the spinning magnets that can't get cooled.

Went its DIY you can hunt around for a rainbow deal.

ACmotor, what do you think the Peak Power for 30min would be for a 50kG Induction motor.

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Post by 7circle » Mon, 15 Nov 2010, 08:49

[Edit Typeos]
Looked for the Auction Listing for Machinery at the Old Engine Plant at Fishermans Bend (Holden)

Big pdf link

Page 57 has a "FOUNDRY STORES INVENTORY" list of motors.
Like 2 x 22kW WEG. etc

3 Pallets - 6 electric motors - 12kw/75kw

I'm taling heaps and heaps of motors... for the next few pages.

So if yo don't get it directly at the Aution I wonder if Ebay will be overflowing.
These stock levels of second hand gear can't all be stored for breakdowns for the next ten years. (maybe they ship off to India or ... NZ)

I'm surprised they can do it, the military used to bury all their old stuff so they wont influence the market.

I hope it will be replaced with a EV battery and motor plant.

[Edits added]
Last edited by 7circle on Sun, 14 Nov 2010, 21:59, edited 1 time in total.

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Johny
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AC motors, amping it up. :P

Post by Johny » Fri, 21 Jan 2011, 19:22

Presuming the AC motor nuts are still subscribed to this thread.

During commissioning the Motor/Controller combination for the Vogue I happened across something that I had misinterpreted.
During autotune to base the motor at 100Hz (I had reason), I had to enter the full-load RPM. The 50Hz full load RPM is 1460 - so I assumed 2920.
I have assumed until now that ACIM slip was a percentage.
Then I found this example for running a motor at 87Hz:
Image
Essentially they are saying use Delta current but Star voltage - that's OK.
But then they calculate full load RPM to be the rated speed (50Hz) RPM plus root 3 no-load RPM.
Doing the equivalent for 100Hz would result in 2960, not 2920 RPM.

As it turns out none of it mattered because I had to use the shaft encoder anyway but it's interesting. BTW 600 PPR appears to be fine - full stability at least under no load (which appears to be worst case).

What did anyone else think slip calculation with variable speed is/was the case.


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Richo
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AC motors, amping it up. :P

Post by Richo » Fri, 21 Jan 2011, 20:50

I thought it was related to load ie Torque
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!

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