Hoisting with Siemens inverter

Autologis

Member
Join Date
May 2014
Location
Dubai
Posts
5
Dear all,

I need some guidance when coming to define the Siemens hardware architecture of a three stage lift automation solution.
I have only theoretical knowledge on PLC from my previous education , I never worked with S7 plc nor inverters.

Main requirements:

  1. Achieve +- 5 mm positioning precision when stopping the lift. load 1200 Kg.
  2. Achieve the desired traveling speed of 0.8 m/s with 0.5m/s2 acceleration
  3. Of course the last one, lowest hardware cost possible.
Motor rated power 9.2 Kw
Inverter rated power 15 Kw.

From my research on the net i chose the following :

Config 1:

The motor is a 4 pole asynchronous to be controlled as 400 V delta with 87 Hz characteristics.
The inverter is a Siemens G120 with CU 250 S controller.
This architecture relies heavily on field bus (PN or DP), and expensive technology modules and encoders.

Questions:

1.Do i need to use encoders to achieve my requirements, speed control, positioning control?
2.Is a speed encoder on motor shaft enough?
3.What is the typical control method for my application.(V/F, vector with encoder, sensorless...) i am really lost with all these possibilities.

I have been asked to submit two solutions for pricing and i would appreciate any guidance and help on any equivalent hardwired solution that meets the requirements !!!

Config 2 :

4.Is there any equivalent solution without using encoders and field buses?

I am thinking about hardwired control from PLC to inverter,
Limit and proximity switches inside the lift to achieve slow down and stopping functions.

5.Does a hard wired solution do the job?

Thanks,
 
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CU250S is servo control unit and it can be with USS, CAN, PROFIBUS or PROFINET fieldbus. As it is servo it requires encoder or resolver. Speed encoder on motor shaft can do the job, but I would prefer one more for security reasons. You need fieldbus because you need very fast communication. From my experience I would prefer in this situation CAN over USS, DP, and PN, because speed and reliability. Encoder will be directly connected to drive not to PLC. Limit and Proximity switches will be used for security, but regulation would be PID. You will have to install braking resistors, tensometers and safety relays also. Motor has to have brake incorporated.

There is CU250V, which is vector control unit.
 
Hello goghie, thanks for your reply,

CU250 S 2 works for asynchronous induction motors.

Inverter + speed encoder on motor shaft + profibus DP + PLC + limit switches for over travel and fine positioning is a very good solution.

But i am asked to propose a 2nd solution without field bus, without encoders, only proximity and limit switches for over travel and positioning and the inverter is directly controlled by PLC through hard wiring on inverter IOs.

Is this 2nd solution even possible to achieve the requirements? Do you have any idea if this solution works?
 
Yes, I know it can work with asynchronous induction motor, but for closed loop you will need encoder or resolver.
Taking in consideration that you need to lift up and down weight from 0 to 1200kg, with that precision and that speed I don't think it can be done without closed loop, even with good brake and all that reduction (9,2kW motor with 1200kg weight). Also, I hope that weight is not live one (people) and fixed and that things like wind do not interfere.
 
In fact there are two lifts with 12 conveyor positions and it is for pallets. Reduction ratio and sprocket diameter will be defined at a later stage.

Thanks a lot for your help goghie, i will update this thread with my final solution.
 
This is Vacon drive but I've done it with Siemens drive also.
Laser measure is more simple than what ever engoder.
Don't ever connect encoder to Drive if you have PLC, anyhow you need that information in plc.

lift.jpg
 
Hello Seppoalanen, thank you for you post.

Can you please send me these details with better image resolution to my personal address mail?
 
You must consider the stop and start modes of a hoist very carefully. Many drives are capable of what it called "torque proving" for use on hoists with mechanical safety brakes. The issue is, if you are parked and the brake is set, then you want to move (up or down does not matter), you must release the brake first. If you release the brake and the load starts to descend (gravity sucks!), it can take much more torque to STOP that moving load than it does to move it, and usually a motor is sized for normal torque for normal moves. If your VFD takes even a fraction of a second to make the motor produce the right toque, the load my run away and drop. Not good.

A torque proving algorithm feed forward into a Flux Vector Control loop is something that REQUIRES a hard motor shaft position from an encoder. You cannot accomplish this in any kind of encoder less vector control method, because they require a moment for the mP to determine the motor model and error to calculate the proper vectors, and that is the moment that allows the load to run away on you on a hoist.

Not all hoist systems need this, such as high ratio right angle worm drives that lock in place without the need for a mechanical parking brake. So you must start there to know the load requirements before you can take it further.
 
I agree a kit with jraef! Do not try to use easier or cheaper solution, but the secure one... At the end your sign will be in project and your responsibility. When it is about lifts there should be some local regulative which you need to obey. In my country there is very strict standardization what you can and what you can't do and install.
Although I do not have experience with laser measuring, I am very reserved regarding security risks.
 
It strikes me as exceedingly dangerous for a tech with as little background and experience as the OP reports he has to be working on one of the most dangerous and challenging VFD and control applications out there.

My suggestion would be to step aside and hire an experienced and certified hoist drive specialist. Look over his shoulder and learn all you can.

Otherwise, the risks are huge--big enough to ruin a young career and leave the OP with blood on his hands. Neither would be good.
 
Hoisting with Siemens drive

Thank you all for your help,

The final hardware config is as follows:

Drive control unit: CU250 S 2 PN : 6SL3246-0BA22-1FA0
Drive: G120 standard 18,5 Kw High overload
Brake Motor: SEW DRE 11 Kw - 4 pole asynchronous
Incremental encoder on motor : HTL 1024 double channel + 0 track
Positioning encoder: SSI Laser encoder from Sick DL100 series
Both encoders are wired to the CU250
Basic safety is included in the control unit for STO SBC SS1
Extra Epos positioning license
14 Kw braking resistor

Safety:

Pilz safety relay with delayed OFF. Delayed double channel for safety linked to the F-DI of the control unit,

Commissioning:

The motor needs to be decoupled from the load to perform motor parameter identification with motor rotating. Otherwise closed loop control will be unstable.

Important for safety: Drive behavior after encoder failure should be configured, by default the drive will go into free fall !!!
p0491 Motor encoder fault response ENCODER / Fault resp ENCODER
Value:
0: Encoder fault results in OFF2. !!! Free fall !!!!
1: Enc fault results in encoderless oper. and oper. continues
2: Encoder fault results in encoderless operation and OFF1. !!! Motor will stop with normal ramp !!!
3: Encoder fault results in encoderless operation and OFF3. !!! Motor will stop with configured safety ramp !!!
4: Encoder fault results in DC braking
5: Enc fault results in encoderless op, operation continues, alarm

I hope this post will help fro hoisting applications, the solution is working without problems since may 2015,

Regards,
 
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