Powerflex 700 linked to external resistance

IMCS

Member
Join Date
Sep 2011
Location
Tunisia
Posts
5
hi all

I have a PowerFlex 700 linked to a large inertia motor so we have installed an external resistance to brake in a definite time, but it has been not worked
Can someone help me?

thanks
 
I would suggest reading the manual or posting all the necessary info needed to help.
 
Yes, certainly I've done everything I've seen a suitable from manual
Possible, but I forgot one of paramteres
 
88----> 1
153---> -50%
145---> 0
155---> 1
156---> 1
157---> 0
158---> 62
159---> 0
160---> 450
161---> 0
162---> 0
163---> 1
164---> 1500
165---> 1000
166---> 0
 
Based on your parameters, you have not enabled braking.

Please read the desciptions for 155,159,161,

And most importantly 163, which tells you that 161 cannot be 0.
 
For those of you reading along at home, these parameters are:

88----> 1 Speed/Torque Mode= Speed Regulator
153---> -50% Regen Power Limit= -50% (default). User Manual says "when using an external dynamic brake, set this parameter to its maximum value (0.0%).
145---> 0 DB While Stopped = Disabled
155---> 1 Stop Mode A = Ramp
156---> 1 Stop Mode B = Ramp
157---> 0 DC Brake Level Select = Parameter 158, DC Brake Lvl
158---> 62 DC Brake Level = 6.2 A
159---> 0 DC Brake Time = 0
160---> 450 Bus Reg Gain Ki (default = 450)
161---> 0 Bus Reg Mode A = Disabled
162---> 0 Bus Reg Mode B = Disabled

163---> 1 DB Resistor Type = External
164---> 1500 Bus Reg Gain Kp = 1500 (default)
165---> 1000 Bus Reg Gain Kd = 1000 (default)
166---> 0 Flux Braking = Disabled

The essential problem that Damien has pointed out is that the External Dynamic Brake resistor is connected, but the Bus Regulation Mode isn't set to use it.

PowerFlex 700 drives have multiple ways to slow down heavy loads; they can regenerate to the line, they can bleed the energy to a resistor, they can extend the deceleration time to limit the bus voltage rise, or they can inject DC into the windings to brake fast.

It may be that all IMCS has to do is enable dynamic braking by setting Parameters 161 and 162 to "2" and set the Regen Power Limit = 0.0%. His application might be more sophisticated than that, but it's a place to start.
 
If you are running an external resistor I would set P153 to the maximum which is -800, depending on the wattage of your external resistor. not zero as zero is the minimum value.
Remember this is the regen power so it is flowing out of the drive this is why it is expressed as a negative value, and the bigger the number in the negative the more power the brake resistor will let through to the external resistor.

Alan
 
Last edited:
The manual confused me, because -800% is listed as the Minimum value and 0.0% is listed as the Maximum value. Silly negative magnitudes ! Thank you for the correction; -800% is the "largest" setting for the Regen Power Limit, and will allow the most power to be sent to the dynamic brake resistor.

The PowerFlex 70/700 Reference Manual has more to say about the Regen Power Limit parameter:

The [Regen Power Lim] is programmed as a percentage of the rated power. The
mechanical energy that is transformed into electrical power during a deceleration or
overhauling load condition is clamped at this level. Without the proper limit, a bus
overvoltage may occur.
When using the bus regulator [Regen Power Lim] can be left at factory default, –
50%. When using dynamic braking or a regenerative supply, [Regen Power Lim]
can be set to the most negative limit possible (–800%). When the user has dynamic
braking or regenerative supply, but wishes to limit the power to the dynamic brake
or regenerative supply, [Regen Power Lim] can be set to a level specified by the
user.
 
Last edited:
Unfortunately Drive Executive does the same thing, makes it very confusing, was able to help a customer over the phone with this once on a hoist saved me a 6hr trip to site and the customer was happy not to have to pay for me to come to site (it would have been 2 flights jut to get to site).

Alan
 
In reality though no drive less than 150 HP will ever shunt more than -500%

-800% is the way the firmware is written.

If you set it to -500% or -400% you will get the exact same result as -800%
 
-800% may can't be written by drivetools,you'd use the HMI to set this parameter.

Another one,me & my mates always set parameter 155 to DC BRAKE or FAST BRAKE,'cuz in heavy load situaion,RAMP can't make motor stop properly,little slip out may happen.
 
-800% may can't be written by drivetools,you'd use the HMI to set this parameter.

Another one,me & my mates always set parameter 155 to DC BRAKE or FAST BRAKE,'cuz in heavy load situaion,RAMP can't make motor stop properly,little slip out may happen.
I certainly don't agree with your last statement about ramp to stop not being as good as DC injection. If your drive is set up for sensorless or flux vector, you should be able to take the motor to zero speed and hold it there at full torque for at least a minute or two.

The problem with DC injection is that the stopping time will vary with different loads on the motor. Ramp to stop will always be the same stopping ramp regardless of load.
 

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