Confused on parameter 82 and actual motor speed on PowerFlex 70 ?

wendaiyu

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Jun 2014
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toronto
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Hi, guys, I am confused on parameter 82, PowerFlex 70.

082 Maximum Speed:
default: 50 or 60 HZ,
min/max: 5.0/500.0 HZ.

Now, we have a motor (60HZ, 1725rpm),

If there is 30 HZ displayed on the drive, what’s the actual motor speed difference 082=60 HZ and 082=300 HZ ?


And we checked the PLC program, there is a function:
actual motor speed (rpm) = XXX (type: int.) / 252.2 * 28

could someone tell us where XXX and 252.2 come from and what their meaning are?

(we know Z = 1725 (rpm) * Y / 60 (HZ) = 28.75 Y.)

Thanks a lot.
 
First off, there are a few important parameters in the PF70:
196 - might need set to "1" to allow access to other params
298 - This determines if the speed feedback to the PLC is scaled by param 55(default) or param 82.

55 - Maximum frequency the drive is allowed to produce (default 130Hz)
82 - Maximum speed the drive is allowed to produce (default 60hz?)

Now to your questions:
1. If the drive displays 30Hz, that is the ACTUAL frequency it is outputting to the motor. So your answer is 30Hz. Since your motor is 1725RPM that would be 30/60*1725 = 862.5 RPM

2. Now the confusing part. The PLC will receive a signal from the drive in the range of 0-32767. How this is scaled depends upon param 298.
(298 = 0) The Speed F/B is scaled (0-32767) = (0 - param 55 value)
(298 = 1) The Speed F/B is scaled (0-32767) = (0 - param 82 value)

There are some confusing things with all of this. My recommedation of how to set it up is:
Param 298 = 1
Param 55 = 130 (Default)
Param 82 = desired max speed (60hz?)

This will make your PLC F/B scaled such that 0-60Hz = 0-32767

The numbers that you are asking about are converting 0-32676 to 0-100% speed. Also included in this would probably be some conversion of motor RPM to machine RPM due to gearing.

Sorry if that's all confusing - I'm doing this quick.
 
Hi, could you tell us what the difference from Standard Control and Enhanced Control is? Are they different devices or softwares?

Because we set para 196 to 1 on PowerFlex 70 via HIM (20-HIM-A3), then we searched para 298. But there was an error showed up: Parameter not Accessible.

Thanks for your time.
 
Checking the manual - 298 does not exist for std control. I don't know if that is an upgradeable thing or not. I know that you order a drive as std or enhanced.

Since it is the default for enhanced drives, I would assume that your speed feedback will be 0-32767 scaled 0-{param 55}.

So here is where it can get confusing:

If you want the motor to actually run full speed (60hz), you need to set param 82 = 60hz. Additionally, param 83 needs to be something greater than 0 (10Hz is default). This is the allowable overspeed - if you command the drive to run at 60 Hz and the drive's speed regulation circuit determines it is going a little slow, it needs to be able to "overspeed" the output freq a little bit (say 62 Hz) in order to achieve the commanded 60Hz.

With this in place (param 82=60, param 83=10), the maximum freq (param 55) MUST be greater than {60 + 10} (the drive won't let you set them otherwise).

If you would set param 82=60, param 83=0, param 55=60, you will be at risk of faulting out the drive when your are commanding it to run at or near 60hz (I forget the fault number that occurs).

I've often seen drives set with param 55 = 120 (2 x param82). With this, the drive speed will not exceed the value of param 82, but what it means is that your speed command to the drive and speed feedback from the drive will be scaled 0-32767/2 = 16383.

If you give the drive a speed command between (16383 - 32767), the drive will just remain at maximum speed (param 82).

Hope it helps.
 

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