S
SQLit
Guest
"dhananjay" <bandyaggroup@yahoo.co.in> wrote in message
news:a63783ae.0503152256.3a5be864@posting.google.com...
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support.
D
dhananjay
Guest
Hello,
Our chemical plant is having a crane (40/5 Te) with MH, CT, LT motion
and was operated by slip ring motor (for two speeds 100% & 10%) with
rotor resistance control (may be and mechanical gear boxes) by our
electrical and mechanical operators etc, i am an electronic engineer
and been called to take the job 'now', as the installation is changed
to an induction motor with ALTIVAR 58 drive (flux vector control
sensorless)for MH and ALTIVAR 28 drive for CT, LT.
The queries are as following regarding this
1) the literature says that the 58 drive is a sensorless flux vector
control but has an encoder card option for speed control? also it says
that there is a series called ALTIVAR 58F which is flux vector control
with or without sensor and is recomendaded for material handling
operations, vertical and horizontal where high dynamics and precision
etc is required, i have learnt while searching the postings that, for
crane applications it is good to have a FVC drive in close loop etc,
so now i dont understand that after puting the encoder card to altivar
58, will it become a close loop FVC? ALso the term "sensor" in the
literature i guess, does not refer to the speed sensor, is it so ?(the
58F drive which is titled as flux vector control with sensor is also
having an option card for speed feedback), so what is this sensor and
how the drive can function with or without this sensor?
2)i am also not sure which type of control this drive uses in its
algorithms, how can i understand is it indirect or direct torque
control?
3)also the literature of ALTIVAR 58F suggests that DC injection
braking is not compatible with FVC close loop and sugests dynamic
braking, since we have ALTIVAR58 and there is no such incompatibility
shown for DC injection braking i have a doubt regarding this as
follows: for crane application which is good combination "DC
injection braking, dynamic braking resistor and openloop FVC drive
(our installation)" OR "FVC close loop drive (like altivar 58f) AND no
DC injection braking (dynamic resistor braking in its place)"
considering the safety?
also why is it incompatible, please explain?
D'jay
16 mar 2005
Our chemical plant is having a crane (40/5 Te) with MH, CT, LT motion
and was operated by slip ring motor (for two speeds 100% & 10%) with
rotor resistance control (may be and mechanical gear boxes) by our
electrical and mechanical operators etc, i am an electronic engineer
and been called to take the job 'now', as the installation is changed
to an induction motor with ALTIVAR 58 drive (flux vector control
sensorless)for MH and ALTIVAR 28 drive for CT, LT.
The queries are as following regarding this
1) the literature says that the 58 drive is a sensorless flux vector
control but has an encoder card option for speed control? also it says
that there is a series called ALTIVAR 58F which is flux vector control
with or without sensor and is recomendaded for material handling
operations, vertical and horizontal where high dynamics and precision
etc is required, i have learnt while searching the postings that, for
crane applications it is good to have a FVC drive in close loop etc,
so now i dont understand that after puting the encoder card to altivar
58, will it become a close loop FVC? ALso the term "sensor" in the
literature i guess, does not refer to the speed sensor, is it so ?(the
58F drive which is titled as flux vector control with sensor is also
having an option card for speed feedback), so what is this sensor and
how the drive can function with or without this sensor?
2)i am also not sure which type of control this drive uses in its
algorithms, how can i understand is it indirect or direct torque
control?
3)also the literature of ALTIVAR 58F suggests that DC injection
braking is not compatible with FVC close loop and sugests dynamic
braking, since we have ALTIVAR58 and there is no such incompatibility
shown for DC injection braking i have a doubt regarding this as
follows: for crane application which is good combination "DC
injection braking, dynamic braking resistor and openloop FVC drive
(our installation)" OR "FVC close loop drive (like altivar 58f) AND no
DC injection braking (dynamic resistor braking in its place)"
considering the safety?
also why is it incompatible, please explain?
D'jay
16 mar 2005
C
Cameron Dorrough
Guest
"dhananjay" <bandyaggroup@yahoo.co.in> wrote in message
news:a63783ae.0503152256.3a5be864@posting.google.com...
variable speed drives - and there is plenty of info available on the Web -
but to get you going:
For your Hoist control, you should fit an encoder card wired to a suitable
rotary encoder (possibly the 'sensor' you speak of) on the shaft of the
hoist motor. This will allow the drive to ensure you don't get 'slip' or
'drop' when the hoist stops with a load on board.
For both the Hoist and Travel drives you will need to fit braking resistors
(Dynamic Braking) to enable the drives to properly stop the crane. When the
crane is decelerating (stopping) there is a large amount of energy that
needs to be dissipated and if you use DC Injection the drive will likely
fail and your crane will crash.
Have fun,
Cameron
news:a63783ae.0503152256.3a5be864@posting.google.com...
D'jay, it sounds like you need to do some reading up on the operation of
variable speed drives - and there is plenty of info available on the Web -
but to get you going:
For your Hoist control, you should fit an encoder card wired to a suitable
rotary encoder (possibly the 'sensor' you speak of) on the shaft of the
hoist motor. This will allow the drive to ensure you don't get 'slip' or
'drop' when the hoist stops with a load on board.
For both the Hoist and Travel drives you will need to fit braking resistors
(Dynamic Braking) to enable the drives to properly stop the crane. When the
crane is decelerating (stopping) there is a large amount of energy that
needs to be dissipated and if you use DC Injection the drive will likely
fail and your crane will crash.
Have fun,
Cameron
T
Terry Given
Guest
dhananjay wrote:
To be honest, google the damned thing.
An altivar 58F is an IP55 Altivar 58.
I cant be bothered researching the Altivar 58 sensorless algorithm, but
invariably sensorless operation is not as good as that obtained with a
speed sensor. Sensorless Flux Vector Control (SFVC) algorithms have some
method of estimating rotor speed. A common technique is to estimate flux
by integrating the output voltage (less the IR drop). SFVC algorithms
invariably have problems at very low speed, as the output voltage is is
no longer large compared with the voltage drop across the IGBTs, so
obtaining an accurate measure (often its an estimate) becomes tricky.
Accurate values of stator resistance are required, and this can be quite
a challenge, especially since its all over the show with temperature.
Not to mention the fact that an integrator becomes a right PITA at very
low speeds (slow response, runs away with small errors, stuff like
that). Ultimately if you need really good dynamic performance, a speed
sensor is required.
A sensorless FOC set to zero speed (ie hold shaft still) will be a lot
"softer" than one with a sensor - IOW if you do this, then load the
shaft with a torque (eg a 1m lever with 3 fat people standing on it) the
shaft will turn far more without the sensor. some sensorless drives I
have played with are so bad (using little 1kW setups) that you can spin
the shaft by hand (albeit with some effort). OTOH with a sensor the
shaft wont budge at all.
Its not that surprising really - if you dont look at the shaft, it is
rather hard to tell if it *really* moves. Whereas if you do look, its
rather trivial. Problem is, encoders are expensive and fragile, and if
not correctly aligned they will flog themselves to bits.
As to how the controller can use (or not use) the speed sensor, its
easy. If the speed sensor input is not doing anything, the SFVCA just
uses its estimated speed. OTOH if it can see the speed sensor is doing
something (or perhaps you tell it the sensor is connected) then it uses
that for an actual shaft speed measurement.
DTC is an algorithm that runs at the IGBT switching frequency, and uses
measured voltages and currents to estimate torque error, then chooses
the most appropriate set of switch states to force the torque error to
zero. In theory its really good, in practice very few companies use it
(ABB does, and they sank many tens of millions of dollars into making it
work right)
Direct and Indirect refer to the type of Field-Oriented Control implemented.
Direct FOC either measures or estimates (from I,V) flux and torque, and
controls them (usually with synchonous PI controllers)
Indirect FOC regulates torque by controlling Iq and slip speed, and
regulates machine flux by controlling Id (note there are 2 definitions
of Id and Iq, which are exactly opposite, just for fun)
IMO stator flux oriented DFOC is far better than IFOC, because there are
a hell of a lot less parameters involved - meaning fewer calculations
(ie higher torque bandwidth for a given processor speed) and greatly
reduced sensitivity (if it doesnt use, say, rotor resistance at all in
the algorithm, then who gives a shit how bad the estimate is)
supports it. But DC injection braking, by definition, dumps all of the
braking energy into the stator of the machine. If you dont have much
energy to throw away, DC injection braking is nice and cheap. If you
have a lot of energy to throw away it gets expensive, as the machine
will cook and need replacing. A big machine has a very low
surface-area-to-volume ratio, so is terrible at getting rid of heat.
This thermal time constraint further hampers the dynamic response
available from DCIB. DB resistors are designed to have massive SA/V
ratios, and get really, really hot - many hundreds of degrees C. On a
cold day, standing next to a 400kW DB running full tit is nice.
In the case of a crane, when you are lowering a load then you must dump
the change in gravitational potential energy of the load, i.e.
m*g*(start_height - finish_height). This is usually a LOT. If you try to
use DC injection braking you will likely cook the machine and drop the
load, quite possibly killing people. This is bad.
Terry
The sensor referred to is a (quadrature) encoder for measuring shaft speed.
To be honest, google the damned thing.
An altivar 58F is an IP55 Altivar 58.
I cant be bothered researching the Altivar 58 sensorless algorithm, but
invariably sensorless operation is not as good as that obtained with a
speed sensor. Sensorless Flux Vector Control (SFVC) algorithms have some
method of estimating rotor speed. A common technique is to estimate flux
by integrating the output voltage (less the IR drop). SFVC algorithms
invariably have problems at very low speed, as the output voltage is is
no longer large compared with the voltage drop across the IGBTs, so
obtaining an accurate measure (often its an estimate) becomes tricky.
Accurate values of stator resistance are required, and this can be quite
a challenge, especially since its all over the show with temperature.
Not to mention the fact that an integrator becomes a right PITA at very
low speeds (slow response, runs away with small errors, stuff like
that). Ultimately if you need really good dynamic performance, a speed
sensor is required.
A sensorless FOC set to zero speed (ie hold shaft still) will be a lot
"softer" than one with a sensor - IOW if you do this, then load the
shaft with a torque (eg a 1m lever with 3 fat people standing on it) the
shaft will turn far more without the sensor. some sensorless drives I
have played with are so bad (using little 1kW setups) that you can spin
the shaft by hand (albeit with some effort). OTOH with a sensor the
shaft wont budge at all.
Its not that surprising really - if you dont look at the shaft, it is
rather hard to tell if it *really* moves. Whereas if you do look, its
rather trivial. Problem is, encoders are expensive and fragile, and if
not correctly aligned they will flog themselves to bits.
As to how the controller can use (or not use) the speed sensor, its
easy. If the speed sensor input is not doing anything, the SFVCA just
uses its estimated speed. OTOH if it can see the speed sensor is doing
something (or perhaps you tell it the sensor is connected) then it uses
that for an actual shaft speed measurement.
there isnt really any such thing as "indirect torque control"
DTC is an algorithm that runs at the IGBT switching frequency, and uses
measured voltages and currents to estimate torque error, then chooses
the most appropriate set of switch states to force the torque error to
zero. In theory its really good, in practice very few companies use it
(ABB does, and they sank many tens of millions of dollars into making it
work right)
Direct and Indirect refer to the type of Field-Oriented Control implemented.
Direct FOC either measures or estimates (from I,V) flux and torque, and
controls them (usually with synchonous PI controllers)
Indirect FOC regulates torque by controlling Iq and slip speed, and
regulates machine flux by controlling Id (note there are 2 definitions
of Id and Iq, which are exactly opposite, just for fun)
IMO stator flux oriented DFOC is far better than IFOC, because there are
a hell of a lot less parameters involved - meaning fewer calculations
(ie higher torque bandwidth for a given processor speed) and greatly
reduced sensitivity (if it doesnt use, say, rotor resistance at all in
the algorithm, then who gives a shit how bad the estimate is)
you *can* do DC injection braking with FOC, providing the software
supports it. But DC injection braking, by definition, dumps all of the
braking energy into the stator of the machine. If you dont have much
energy to throw away, DC injection braking is nice and cheap. If you
have a lot of energy to throw away it gets expensive, as the machine
will cook and need replacing. A big machine has a very low
surface-area-to-volume ratio, so is terrible at getting rid of heat.
This thermal time constraint further hampers the dynamic response
available from DCIB. DB resistors are designed to have massive SA/V
ratios, and get really, really hot - many hundreds of degrees C. On a
cold day, standing next to a 400kW DB running full tit is nice.
In the case of a crane, when you are lowering a load then you must dump
the change in gravitational potential energy of the load, i.e.
m*g*(start_height - finish_height). This is usually a LOT. If you try to
use DC injection braking you will likely cook the machine and drop the
load, quite possibly killing people. This is bad.
Cheers
Terry
D
dhananjay
Guest
hi, thanks for your elaborated responce regarding my queries,
literature where the sensor(ed) FVC drive ALtivar58F (as titled), also
has an option card for speed encoder, just like the ALtivar 58 which
has title (as) Sensorless FVC (but it too have an option card for
speed encoder),
so my conclusion was, the sensor these guys are refering to, may not
be a speed sensor, as speed sensor is optional to both, (sensorless
and (with) sensor FVC).
Also regarding the indirect FVC, since that estimates the controlled
variables (torq, speed) indirectly, using I,V etc (position etc), it
may be a sensorless FVC (as it runs on estimation) and one you said as
direct FVC must be the FVC with close loop control (and may be the
altivar 58F with speed encoder option card installed)
since ours is a constant torq application (as said in application
guide of schneider), the controlled loop is of torq and speed
variations may be tolerated and may be thats why the speed sensor is
an optional entity to these FVC drives and not an integral part.
i guess that the speed encoder will be a must accessory and not an
optional card when the drive will be used to synchronise with other
motor speeds or used in constant speed applications.
regarding the holding a load standstill, as per company's catalogs, a
FVC close loop drive (it doesnt mean a speed sensor on a sensorless
FVC(altivar 58), again, the altivar 58F too have an optional speed
encoder card) will be the best. Since mine is having a Altivar 58
(sensorless) and there is no speed encoder either, so i guess it is an
open loop FVC and may not be used to hold the load standstill on its
own.
I think thats why our original mechanical brake assembly is still used
in this new installation as that is default lock (energised to open)
for fail safe condition.
The FVC closeloop too may be useless if there is a power drop/cut to
drive etc in such cases, mechanical brake will be useful in crane type
applications, may be the FVC close loop, without mechanical brakes, is
for the uninterrupted type powered plants.
thank you for arranging my thoughts in this case so fast.
i enjoyed this
D'jay
18 mar 2005
here i guessed that initially,but OP query originated from a product
literature where the sensor(ed) FVC drive ALtivar58F (as titled), also
has an option card for speed encoder, just like the ALtivar 58 which
has title (as) Sensorless FVC (but it too have an option card for
speed encoder),
so my conclusion was, the sensor these guys are refering to, may not
be a speed sensor, as speed sensor is optional to both, (sensorless
and (with) sensor FVC).
Also regarding the indirect FVC, since that estimates the controlled
variables (torq, speed) indirectly, using I,V etc (position etc), it
may be a sensorless FVC (as it runs on estimation) and one you said as
direct FVC must be the FVC with close loop control (and may be the
altivar 58F with speed encoder option card installed)
since ours is a constant torq application (as said in application
guide of schneider), the controlled loop is of torq and speed
variations may be tolerated and may be thats why the speed sensor is
an optional entity to these FVC drives and not an integral part.
i guess that the speed encoder will be a must accessory and not an
optional card when the drive will be used to synchronise with other
motor speeds or used in constant speed applications.
regarding the holding a load standstill, as per company's catalogs, a
FVC close loop drive (it doesnt mean a speed sensor on a sensorless
FVC(altivar 58), again, the altivar 58F too have an optional speed
encoder card) will be the best. Since mine is having a Altivar 58
(sensorless) and there is no speed encoder either, so i guess it is an
open loop FVC and may not be used to hold the load standstill on its
own.
I think thats why our original mechanical brake assembly is still used
in this new installation as that is default lock (energised to open)
for fail safe condition.
The FVC closeloop too may be useless if there is a power drop/cut to
drive etc in such cases, mechanical brake will be useful in crane type
applications, may be the FVC close loop, without mechanical brakes, is
for the uninterrupted type powered plants.
thank you for arranging my thoughts in this case so fast.
i enjoyed this
D'jay
18 mar 2005
T
Terry Given
Guest
dhananjay wrote:
and there are probably a wide variety of add-ons - analogue I/O that
sort of thing.
decouples the amchine into orthogonal torque- and flux-producing
currents, which are then controlled independently (a-la seperately
excited DC machine)
just to add to the confusion, some (not Schneider) manufacturers are
pretty casual with the term "Vector Control" and often use it where its
not deserved (eg if they have a V/Hz controller that uses space-vector
modulation to generate the PWM)
(eg hold full load at zero speed with imperceptible shaft rotation) you
will need an encoder, if its not so tricky you wont.
1) the *interface* to which the encoder attaches. This may or may not be
an option (it probably is)
2) the encoder itself (and mounting hardware, interconnect cable, 6'5"
electrician to wire it up, crate of beer to drink afterwards), which
*you* have to obtain and connect (but is probably available as an option
too, perhaps sans beer)
encoder. The drive itself will work either way. This is particularly
handy when a fitted encoder breaks - the drive can figure this out,
transition to open-loop control and the plant keeps on running. yay for
software
who relishes losing lawsuits.
Cheers
Terry
of course they dont supply the sensor, just a place to connect it
and there are probably a wide variety of add-ons - analogue I/O that
sort of thing.
ultimately its a matter of semantics. A suitable field-orientation
decouples the amchine into orthogonal torque- and flux-producing
currents, which are then controlled independently (a-la seperately
excited DC machine)
just to add to the confusion, some (not Schneider) manufacturers are
pretty casual with the term "Vector Control" and often use it where its
not deserved (eg if they have a V/Hz controller that uses space-vector
modulation to generate the PWM)
it all depends on the dynamic response you require - if its wicked good
(eg hold full load at zero speed with imperceptible shaft rotation) you
will need an encoder, if its not so tricky you wont.
Yes. it will comprise 2 parts:
1) the *interface* to which the encoder attaches. This may or may not be
an option (it probably is)
2) the encoder itself (and mounting hardware, interconnect cable, 6'5"
electrician to wire it up, crate of beer to drink afterwards), which
*you* have to obtain and connect (but is probably available as an option
too, perhaps sans beer)
"closed-" and "open-loop" refer only to the presence or absence of an
encoder. The drive itself will work either way. This is particularly
handy when a fitted encoder breaks - the drive can figure this out,
transition to open-loop control and the plant keeps on running. yay for
software
only a mad bastard implements a crane without a mechanical brake. Or one
who relishes losing lawsuits.
bingo.
You're welcome, I seldom get to think about drives nowadays.
Cheers
Terry