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Stepper Motor Drive P6000 or P5000 for application with a Speed Safety Limit ? | 11 May 2020 | |

Stepper Motor Drive P6000 or P5000 for application with a Speed Safety Limit ?

The design requirements for a mechanical device driven a POWERPAC K/N motor (medium torque) include the determination of some probability figures.

Assuring a Maximum Input Frequency, can the Driver alone speed up the motor over the input Reference ?  to more than 2 times the Nominal Speed ?   We have to estimate the probability of this failure.

To select the Driver in this particular case, is important to know the complexity of the driver:  has a microprocessor inside ?, has an internal Oscillator Circuit that can generate a higher frequency than the input frequency ?,  At least has a MTBF values that can be used to estimate conservatively the Probability figure.


Comments & Answers

jcoleman02 | Mon, 05/11/2020 - 20:28
The stepper drive will run the motor at a commanded speed based on the step resolution setting and the step input frequency.

If you are asking if the drive will run the motor faster than it is being commanded, I've never heard of any stepper drive doing that.  It is not like a servo that can run away under certain failure conditions.  What you are asking is more of a processor failure.  Still, I've never heard of that happening.

For the MTBF:
If you are asking for MTBF for a failure mode of the motor running faster than commanded, we do not have that data, as it has never happened or never identified.
If you are asking for MTBF data for a particular Powerpac motor, contact Kollmorgen Technical Support or a Kollmorgen distributor directly to request that information.

ruca | Mon, 05/11/2020 - 23:52
Thank you very much, Mr jcoleman02.  We appreciate your observations based in your experience.

Still, I wonder to know more about these drivers P5000 and P6000 series.

Wether or Not they include microprocessors  and -in consequence- firmware software determining the motor speed. 
Having software involved restrict to not better than 1E-4 the probability figures.

We will follow your suggestion and ask to the Technical Support about the MTBF figures for P5000 and P6000 drivers.


Dan.Wolke@Koll… | Tue, 05/12/2020 - 11:59
The P5000 and P6000 drive do not have Functional Safety features.  If you want safe speed, you will need to use an additional safety PLC and additional encoder to close the safe speed monitoring loop outside of the Motor/Drive.  I am sorry we were not able to help you.

ruca | Tue, 05/12/2020 - 12:51
Thank you very much for your response, Mr Dan Wolke.

The design is already using externally Safety equipment as you mention.   Never the less, the probabilistic calculations asks for a Drive that has data to calculates its contribution to the total unsafety. 

Is this big uncertainty that focus us to select the simple drive as possible with the better MTBF figures.


ruca | Tue, 05/12/2020 - 13:05
The Field Service said:

"Have a question now? How about a quick Live Chat? Click on the Live Support icon below" 

What does it mean ?   Y could asks for this subject using  facebook, for example ?  Or in my country (Argentine) this possibility is not available. 

jcoleman02 | Tue, 05/12/2020 - 13:22
The P5000 and P6000 drives use microprocessors.  There are no MTBF figures relating to speed control or maintaining a safe speed or maximum speed.  These figures just don't exist.  If you need to monitor speed for safety reasons, then you must use an external safety system to verify speed.  If you are located in South America, you should contact the Kollmorgen office in Brazil for support.

ruca | Tue, 05/12/2020 - 20:37
Thank you very much Mr jcoleman02.  Again.

I am asking for the classical MTBF figures. 

With this data - I understand - we can obtain the probability of any drive failure. All of them, failures with or without safety consequences.

Then, at least, we have a limit. The safety contribution of the drive surely is better than that.  But this number could be enough for approval the total safety design.  We do not need to change this motor and drive for this reason for pass to the following project stage.


ruca | Tue, 05/12/2020 - 21:02
A colleague told me that perhaps I should reformulate:

"The driver executes one step when the STEP input closes (transition from logic "1" to logic "0").

Is there any possible failure mode in which the driver could execute steps when there are no transitions in the STEP input?"


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