Controlling a motor using Hz

[djmitch]

Hi guys, I'm fairly new to PLC programming and I am using Mitsubishi FX series at work. I'm wondering if anyone could point me in the right direction when it comes to controlling a motor with the number of hertz.

We are going to develop a testing machine for sling wear and need to use a motor to move the sling forwards and backwards over a point. The two frequencies that are to be used are 0.05Hz and 0.50Hz and the sling tension will be set at 1 metric tonne. What sort of hardware would you use and what function to control the Hz value.

BTW this is also my first post so sorry if it isn't correct.

 

[nonuke]

What Type of motor?
If its an AC motor, you need a frequency inverter to control it. For those frequencies (very low), you also need a separate powered cooling fan.

 

[jrwb4gbm]

A 100 to 1 ratio gearbox plus a separate cooling fan as mentioned above would allow the motor to run at 5 or 50 Hz.

 

[sunilkumbhar]

A gearbox and use of VFD may solve your problem

 

[strantor]

Maybe it would be better to discuss RPM instead of HZ. And disclose the details 8f your motor if you already have it. How did you arrive at the conclusion that you need to run the motor at .05 and .50 Hz? These values correspond to One electrical cycle every 20 seconds to every 2 seconds. This is outside the range of any VFD. It is not possible. Even if it were possible, it would result in widely varying RPMs depending on how many poles the motor has, etc. So this is why we need to speak in terms of RPM and the desired final outcome, in order to say what is needed to accomplish it. Also disclose torque needed, available power, rpm accuracy, position accuracy, etc. All relevant details.

 

[danatomega]

I'm thinking it's the cyclic rate of the sling testing, not the motor Hz, that's important to the poster.

 

[djmitch]

Hi guys, thank you for the replies. I've been thinking over the weekend whether of not a stepper motor might be more suitable for this task? converting the Hz to RPM would 3 and 30rpm. I was thinking that the VFD might not be able to change the frquency quick enough as strantor stated it could cause varying RPM. The stepper motor would be more accurate and easier to control for backward and forward motion i think? The only information i was given on the hertz is " The frequency of the test is between 0.05 and 0.5 Hz. ". That was copied directly from the email. VERY vague, i shal requestion them.

 

[m_reavis]

I am trying to learn how write a program to modulate several in-feed conveyors with different gear boxes to follow a production machine. The system uses the Power Flex 525 drives on a Ethernet network. I don't mind doing the work but haven't got a clue as to how to start or which programming instruction or instructions would be used. Any ideas or pointers would be greatly appreciated.