Re: Precise Speed Applications
Your question is difficult to answer in a simple way.
There are many means to regulate the conveyor motor's speed to a setpoint such as inverters, fluid clutches, DC solid-state rectifier regulators
There are a number of factors that induce error:
1. motor design such as electrical slip <1-3% depending or rotor design; AC-asynchronous, AC-synchronous, DC
2. AC-asynchronous ( most common electrical motor design) motor size - motor slip can be controlled to a tighter and lower electrical slip with a higher design load: 2% for small motors and down to < 0.8 % for large designs with an A NEMA equivalent slip rated eff.
3. instrumentation: speed loop error control - operating over the motors AC-asynchronous speed range would make maintaining to <1% of the selected speed significantly more difficult than to 1% of full speed.. So its impoortant to know if your speed setpoint will be fixed or variable. Other motor designs will require different control strategies.
Your question on a need for speed and position accuracy: one application is in the automotive chain drives on their assembly lines. A second application, but not conveyor related, might be a AC-generator which needs to run at the grid line frequency usually within +/- 1%. These are accomplished by AC-sychronous motors. But, then you get inot power-factor correction and lead-lag phase angle adjustments which distort the target setpoint.
If acceleration control is not an issue, then use a AC-sychronous motor that runs at a constant RPM regardless of demand load, unlike a AC-asynchronous motor where the motor speed varies with load. ■
Re: Precise Speed Applications
When using an inverter at the low end of the motors speed range you may experience cogging or percetable speed changes that wil exceed 1% due to the step configuration of the rebuilt AC sine wave. Some inverters have a 6 step wave form others 12 step or others a pulse width modulated ( higher steps at the low speed range starting at 24 steps more or less).
As previoulsy stated, accuracy will depend on the conveyor speed range and target. ■
Re: Precise Speed Applications
Ok.
So as long as the speed range isn't great, the best way to achieve a precise speed is to use a synchronous motor with the proper mechanical gear ratio. ■
Re: Precise Speed Applications
There is no allowable deviation in speed or in other words there is no speed range of a synchronous motor unless a cycloconverter (type of inverter) is applied to regulate speed.
THe synchronous motor will deliver to the accuracy of your lelectrical line frequency variation. ■
Re: Precise Speed Applications
Okay. Thanks
So you saying there are very few applications that requires a very precise conveyor speed? ■
Re: Precise Speed Applications
Originally posted by unclehan
Okay. Thanks
So you saying there are very few applications that requires a very precise conveyor speed?
Usually, small packaging conveyors require exact speed, this is usually achieved using Servo motors. ■
Precise speed applications
Are there any applications where the speed of the conveyor needs to be as precise as possible?
Can you list some?
What's the best way to achieve a very exact speed? Let's say I want to have the conveyor speed to be within 1% of 0.5 m/s at all times.
If VFD the only way to achieve this? Or can it also be achieved with the proper motor selection and mechanical gears?
Thanks ■