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Author Topic: CS Labs CSMIO/P-A  (Read 15180 times)

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Re: CS Labs CSMIO/P-A
« Reply #200 on: August 06, 2018, 01:43:47 PM »
Hi Craig

Thank for taking the time on this. This is definitely something which needs checking prior to going for the Servo Spindle. We run an 8kw heat pump which gets used a lot through the winter. Excuse me for being thick but can you please explain a little more. I apologise if you have already covered this.

the first motor:

power =2600 X 2 X PI / 60 X 19
          =5172 W

the second:
power = 3000 X 2 X PI / 60 X 14
          =4397 W


I don't understand why we are getting 4397w when the motor is rated at 3000w

The motor on the lathe at the moment is 6kw at 65HZ at 1950 rpm at 15A according to the plate. Can we run this motor at full speed and use a clamp meter to check the amp draw. Taking away assumptions of the power factors. Then work back from this with the servo motor ratings?     

Cheers
Mick
Re: CS Labs CSMIO/P-A
« Reply #201 on: August 06, 2018, 03:19:50 PM »
Hi Mick,

Quote
I don't understand why we are getting 4397w when the motor is rated at 3000w

Nor do I but you provided the torque and speed figures. The shaft output is just that, it has no bearing on the electrical
means by which it was generated and the calculation is exactly as Isaac Newton proposed.

My guess is that the torque figure supplied was somewhat higher than its 'rated torque' The motor does not just stop when its gets
to its rated torque, if the drive produces yet more current the motor will produce yet more torque and therefore power to the load. Over a period
of time you might expect it to overheat. The 'rated' output is more about a thermal condition rather than an absolute limit.

There are two figures of merit that apply to servos which can be relied on to produce accurate numbers. The first, called the torque constant or Ka
is in so many 'Nm per Amp' Thus if a motor is supplied 10A and its Ka is 0.95 Nm/a then its torque at that operating condition is 9.5Nm.
The second is called the back EMF constant or Kv in so many 'Volts per 1000 rpm' or some other equivalent units. Thus a motor spinning at 2000 rpm
with a Kv of 100 V/1000rpm will have a back emf of 200V. If our supply is 230V, the motor cannot run much faster as the back emf is close to defeating
the applied voltage.

The two numbers relate very much to the design and construction of the motor. In general we want Ka to be high, that is a motor than can produce
a lot of torque from a small current. For instance you might decide to have a high number of turns in the stator so that it produces a strong magnetic
flux for a given current and choose high strength rare earth permanent magnets  for the armature.

Both of these however increase Kv also, and as we have seen its the back emf that determines the motors top speed for a given input voltage.
You came across an example yesterday where a servo produced high torque up to 2600rmp and then seemed to die. The Kv figure is such that the servos top
speed with 230V input is 2600 rpm. To get it to go faster you have to artificially manipulate its Kv, which can be done, within limits, with field oriented control
with a technique called field weakening.

Craig
My wife left with my best friend...
     and I miss him!
Re: CS Labs CSMIO/P-A
« Reply #202 on: August 06, 2018, 03:38:25 PM »
Hi Craig
Thank you for the detailed explanation but I am more confused now. Can we check the amp draw via a clamp amp meter using my existing motor to confirm the draw and not be guessing power factors and everything else that's drawing power?

Cheers
Mick
Re: CS Labs CSMIO/P-A
« Reply #203 on: August 06, 2018, 07:28:01 PM »
Hi,
thats not going to be easy...how do you intend the load your existing spindle to rated output?
I would be less concerned about your existing spindle, its likely to have a power factor of 0.8, not
great but not too bad either. Likewise your single to three phase converter is likely to be very good.

The trouble comes when you fit a servo drive, they have a simple rectifier input and could draw much
more current than you think. Without one to test and some means of loading it to rated output
you won't know.

Given that the current is drawn in pulses even supposed 'real rms reading' meters are not really that good.
Thus you would need some good gear to make effective measurements. By that stage you already have
your drive and servo....its a bit late to decide you don't want it after all.

Clearly you have made some allowance for increased current draw at the time you fitted your converter, I would
think you can afford to box on. If it proves that the current draw is excessive then you will just have to back
off your demand....which you can set by taking a lighter cut...OR...setting a realistic current limit by programming
your drive.

Your 100A supply and 50-60A breaker should allow you to proceed safely. As I have said before its actually really hard
to load up motor that much, you may find that all of these precautions are uneccessary.

Craig
My wife left with my best friend...
     and I miss him!
Re: CS Labs CSMIO/P-A
« Reply #204 on: August 07, 2018, 01:11:07 AM »
Hi Craig

Thank you.

The other thing I would need to buy is 3 phase step down transformer. The 3 phase drives are 220v 3 phase and the converter puts out 430v.

Cheers
Mick 

 
Re: CS Labs CSMIO/P-A
« Reply #205 on: August 07, 2018, 02:49:00 AM »
Hi,
these three phase 200V drives are for the Yanks. There is no need for you to follow suit.

Your converter outputs three 230V-to-neutral phases or 400V line-to line. You should be getting a drive and a servo to accommodate that.

For instance the Allen Bradley numbering goes:
MPL-A430H    where the A stands for 230V and
MPL-B430H    where the B stands for 400V operation. Note that it is common to state the AC line voltage for which the servo/drive is matched
when in actual fact they will operate at the DC Link voltage and the DC Link voltage derived from a 400VAC supply is 560VDC.

Craig
My wife left with my best friend...
     and I miss him!
Re: CS Labs CSMIO/P-A
« Reply #206 on: August 07, 2018, 03:40:28 AM »
Hi,
you have been looking at the Lexium 28 series which are 220V single or 220V three phase units.

You need to look at the Lexium 32 series:

https://www.schneider-electric.com/en/product/LXM32SD30N4/motion-servo-drive---lexium-32---three-phase-supply-voltage-208-480v---3-kw/?range=2302-lexium-32-%26-motors&node=166536672-servo-drives

There you will find 380-480V versions.

Craig
My wife left with my best friend...
     and I miss him!
Re: CS Labs CSMIO/P-A
« Reply #207 on: August 07, 2018, 01:54:31 PM »
Hi Craig

Cheers for the info. did think it was a bit strange for everyone to have to use step down transformers. Will check them out.

Mick
Re: CS Labs CSMIO/P-A
« Reply #208 on: August 07, 2018, 05:01:02 PM »
Hi

Does anyone have a spindle torque calculator to hand? Where I can input stock diameter, material, feed rates etc. Going round in circles on the net.

Cheers 
Re: CS Labs CSMIO/P-A
« Reply #209 on: August 07, 2018, 06:03:03 PM »
Hi Mick,
HSM Advisor, liked it so much i bought it.

Craig
My wife left with my best friend...
     and I miss him!