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07-06-2010, 05:57 PM #1
OT:Servomotor conversion to std motor w/ VFD
Customer brought me a machine used in the food industry.
Came to me disassembled, used to it.
Anyway, the machine portions out food and is driven by a servomotor on the gearcase.
Servomotor is used to propel the head and I am sure it it used for portion control, CPU reads the rotations and starts/ stops motor and/or controls other accessories.
Problem: servomotor is bad(customer inflicted) among other things.
OEM wants $5k for servomotor
They want $75.00 for a buna o-ring 170x2.0. to give you an idea of their pricing?!
So............turns out customer doesn't want portion control, they have never used it for portion control
They want the machine to feed continuously, controlled by a foot pedal by a human, simple ON/OFF.
So................I say lose the servo and mate a std motor to gearbox. Add a VFD to control motor speed. Program the ramp-up speed to be easy on startup , use "coast to stop" when pedal is released.
Question: servo is rated at 2.4 KW at 3000rpm-19 amp,
A 3 hp std motor is 2.2kw+- @3450,
close enough to swap???
Realize an adapter will/may be needed between new motor and old gearbox.
Anything I don't know about the differences between servos and std motors? ( in the context of this application)
I am assuming they both have approx the same perfomance?
07-06-2010, 06:04 PM #2
Give me the specs on the Servo. I'll see what I can find. If I can find wiring diagrams for an 83 year old machine I might be able to find a third party replacement for you.
07-06-2010, 06:10 PM #3
Nr 962 07828 1F
2.4 Kw IA 64/65
Io 19 Amp
Art nr 255115
Measured an 80 IEC mount face,
165mm bolt holes c/L
130 mm inner flange
Dg 60 K?M ( scratch right acroos the digit)
Strichz 1000 5 v
07-06-2010, 06:15 PM #4
Uh oh, teutonic motors and electronics.
Bad sign IMO.
07-06-2010, 06:25 PM #5
I'll see what I can find. I'll admit that my initial reaction was sweet merciful crap why does he need this?? Servos are like super precise stepper motors. But if the client really doesn't ever want the option for stepper control....VFD's are really expensive. Probably once you get the motor and control and adaptation done, it'll be more expensive than going OEM. We have a VFD on our High pressure spray system that cost us about 10k. That being said...something along the lines of a sewing machine drive (aka buy a cheap one and rip the guts out of it) would probably do what you want. Not sure if you'll be able to find something that will handle the amperage you need.
07-06-2010, 06:33 PM #6
A VFD for this application should be less than $500 - probably way less. If they don't want the servo motor functionality, I think the idea of an induction motor + VFD is a good one. I would use a 3600 rpm, 5Hp 220V three phase motor with a VFD. It should work well as you plan to use it.
07-06-2010, 06:37 PM #7
07-06-2010, 06:52 PM #8
You're reasoning that 5 hp will give me an added edge powerwise using the VFD at slower speeds?
Yes, 3ph no problem. machine is 230 v.
Might get fancy and have 3 preset speeds to help match output of machine.
07-06-2010, 06:58 PM #9
Since the servo has a lower max rpm, it would probably have better low end torque than a 3hp motor. The extra cost is minimal and the 5 Hp motor is not much larger - it seemed better than having to go back later and increase the Hp. No real downside I can see, unless space is at a real premium.
07-07-2010, 09:24 AM #10
The servo will give 100% torque at zero rpm where as the induction motor and vfd would not unless you use a more expensive vector drive. This could be very inportant in an extruder application. I'd definitely go with the 5hp VFD if you are going to change the system design. There are less expensive servo systems out there that could run in velocity mode or position indexing, giving you a lot of flexibility in operation.
07-07-2010, 09:36 AM #11
Yikes - I respectfully want to contradict some of what has been recommended here.
That baumuller motor has less than 10% of inertia of the AC induction motor of similar torque / speed performance. If you need fast accel / decel forget about using an AC motor unless you go closed loop ACVector (i.e. motor with an encoder and a reasonably capable drive)
If you find that the acc/dec requirements are not that aggressive - do yourself a favor and spend a grand on a 5HP drive with built in dynamic braking controller and external braking resisitor and open loop vector capability. When you pick the motor, go TEFC - Baldor makes a reasonably cheap blower cooled motor that would work fine IF - the acc/dec requirements are not stringent.
I have done food portioning machines before - filling ice cream cartons at 90 cartons a minute is NOT in the AC Induction motor realm of performance
And - if you want a Baumuller motor to replace that one - Parker can make you a drop in replacement (the MPM series) for under $3k . . . also I have that Baumuller motor in stock with a different encoder resolution. They are much cheaper if you go to a Baumuller distributor directly instead of through the OEM.
07-07-2010, 10:26 AM #12
The original post said the customer only wanted on/off control. Sure the acceleration will be less with an induction motor, but from the original post - that did not seem to matter.
07-07-2010, 11:41 AM #13
This case may be different, but every food packaging system (and every food container machine) customer I have worked with is so particular about the "amount" of food that goes into the container it is unbelievable. I have been called in to fix a system that would be off by 1/4 ounce on a 20 oz fill.
If this isn't the case - no problem with a VFD.
07-07-2010, 04:33 PM #14
Good point about the acc/dec.
The OEM did design the machine for fairly precise portion control.
Customer never used this function.
Machine is a sausage stuffer.
They use long casings and do not twist.
They do/did have a problem when the machine started, it blew the casing ends out, so I figured I would ramp up the VFD to solve that problem.
Now after reading the last few posts, I may need a brake, thinking that till everything slows down it might push out to much product.?
However during another discussion with customer they drive the unit rather slow.
Measured today and a 5 hp will not fit if bolted up to the OEM gearcase.
So..... will mount the motor shaft down on the side frame, transfer power over with a two sheeve drive to an input shaft. One end of the shaft machined for the gearbox the other supported by bearings. Kind of like a jackshaft type thing. This way I can bring the 3450 5hp down to 3000 via pulleys and gain a little extra grunt and/or change the ratios if I need more bottom end.
"If you find that the acc/dec requirements are not that aggressive - do yourself a favor and spend a grand on a 5HP drive with built in dynamic braking controller and external braking resisitor and open loop vector capability"
Motion what brand type drive were you referring to?
Keeping the servo? Well the overall condition of the electricals is rather poor, has not been the most reliable and has been rather expensive to maintain. So since the customer does not need "servo control" why not reduce the complexity?
Thanks so far guys