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Old June 20th, 2017, 11:11 AM   #1
justblaze
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Powerflex 525 or 755 for encoder speed reference

Good morning,

I have not had much luck getting a direct response from my distributor on this question.
We have an existing chain conveyor system that operates at 1 - 5 meters per minute.
There is an additional chain conveyor being built as an add on and I would like to have it run at the same speed as the upstream conveyor.
We plan to install an incremental encoder on the shaft that drives the chains of the upstream conveyor for a speed reference input to the VFD running the second conveyor.

Would the speed of the second conveyor be accurate with an encoder as a speed reference only or would it need an additional encoder on it's own driven shaft for feedback?

Which of these two drives would be preferred for this application?
I know that either will need encoder interfaces added.

Thanks
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Old June 20th, 2017, 11:35 AM   #2
dmargineau
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An encoder will provide speed feedback.

To generate a speed reference you will need a digital write or an analog signal.

If the 'upstream' (master) VFD provides Analog Output provisions, add the encoder to this system and 'translate' its speed into said Analog Output value.

Then, pick the Analog Output signal and tie it into an Analog Input of the 'downstream' VFD (follower); program said Analog Input as the Speed Reference source for the 'downstream' conveyor VFD.

Most of the mainstream VFDs manufacturers provide Analog I/O signal scaling features in order to achieve synchronicity between 'Masters' and 'Followers'.
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Old June 20th, 2017, 12:45 PM   #3
BlueAltezza
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Are the drive systems identical?

If yes, you can typically set up the original drive to output a voltage/current based on a setting (incoming signal - essentially a pass through, output frequency, output current, etc) and wire that output to the input of the 2nd drive. That would save the hassle and cost of installing the encoder.
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Old June 20th, 2017, 01:26 PM   #4
jraef
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And... define "accurate".
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Old June 20th, 2017, 01:27 PM   #5
AustralIan
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Check out appendix E of 520-UM001.

525 has a built in pulse input that can be used as a speed command. You can also buy an encoder option card to use as the motor feedback.

If you use both the reference encoder and motor feedback encoder you will be able to synchronize the two chain speeds.

Most products you can run one conveyor faster than the other, and the product depth will vary to compensate. In which case you can easily synchronize to the rated slip of the motor doing away with the need for the motor feedback encoder and additional encoder card.

Usually you can get away with configuring an AO from the first VSD as an AI speed reference to the second VSD for an acceptable slip, compensated for by bed level. An offset is sometime used to run the second one either faster or slower depending on your requirements.
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