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Sinamics v20 f2 Fault (Overvoltage) While Running
Overvoltage fault during running on 1/2 HP fan with Siemens v20.

Using v20 to run small fan (1/2 HP) using two speeds, 50% and 100%. After sometime, more than 2 hrs, drive will fault with f2 error. It will switch speeds fine, ramp up and down is 10 seconds as default in application macro. I'm not using any braking resistor, is it necessary for fan application? I could change ramp down to disable, I did this on another drive with no effect on f2.

I actually have two drives like this, other one I wrote some auto fault reset code in the PLC, but second unit is not wired to PLC. I know the incoming power is good, usually around 475 volts, so under voltage if anything.

Suggestions? I could wire it to the PLC and use the fault reset function, but it seems like that's avoiding the problem.

By Steve Myres on 29 November, 2018 - 3:49 pm
1 out of 1 members thought this post was helpful...

The rule of thumb for pumps and blowers is that with a constant system curve, power varies as the third power of speed. That's true, in so far as it goes, but applies only to the power required to move the air. As fans get larger, the impeller gets more than proportionately heavier to be sufficiently rigid. Thus, above a certain power level (rule of thumb 15hp) the starting torque to accelerate may govern motor selection, especially for very high pressures that require more rigid impellers relative to fan power.

So, short answer, no. Fans are not usually an overhauling load in the hp rage you mention, but there may be some cases (heavy impeller, some other force trying to move air through the fan, etc.) where a particular fan might be.

I have one 75hp fan at a customer where I have to have the decel set at 60-90 seconds to avoid a trip. 1/2hp I wouldn't expect it, though.

By Gabriele Corrieri on 29 November, 2018 - 3:50 pm


You did not give some data for troubleshooting: F2 appear in which condition? Running at 50% or 100%? Increasing or decreasing speed? Startup from 0% or stop to 0%? What is the drive plate input voltage? Have you set the P210 correctly? What is the value of the fault sub index R0949?

My idea from my near 25yr spent in this field is that a braking resistor is not the solution, as I read the manual I think that the problem is the power source: 475 V RMS is too high for a converter rated 400V, that produced a 670V DC Bus (instead of 560 for a 400V line) a little regenerative power could be trigger the F2, that I think is around 750V.

Gabriele Corrieri

F2 fault shows up while drive is running at either half or full speed, not during ramping action. I will change deceleration time to higher value.

System voltage is 480v, 3 phase. I have observed the DC bus to rise up to 780v, corresponding increase on AC bus, though another v20 shows no similar increase despite being on the same service.

By Gabriele Corrieri on 2 December, 2018 - 5:26 pm


You've found the problem. If the 2nd or another other V20 under same service doesn't clip with F2 the problem is the load that regenerate energy.

A solution could be a braking module and a braking resistor. But if all the V20 are powered together (not put in run, only powered by AC line), you could put together all DCP and DCN terminal block: the regenerative energy of one is used by other that are in run.

The regerative power at this point could be generated by a wind over the fan that spin up the motor rpm.

Gabriele Corrieri

Is it really possible to wire Dc+ and Dc- of multiple Sinamics v 20 together in series, for the braking resistance without using a proper external resistance?

I never tried it. Are there any risks of damage?

By Steve Myres on 27 August, 2019 - 11:07 am

Parallel, not series, and yes you can do that with VFDs. No idea why V20s would be an exception. Typically, there's a fuse in the branch to each VFD. You might want to keep the braking unit and resistor for cases where there's net regeneration on the group, but it's going to be a lot smaller than if you had a brake unit and resistor for each drive.

1 out of 1 members thought this post was helpful...

There is a parameter (P210 mentioned above sounds right (I don't have a manual handy) that identifies the system voltage to the drive. We've had machines come in set to 400 instead of 480 and they tripped immediately on power-up. If yours is set to 440, for example, it may not trip right away. I would research that parameter and see what it's set to.

I have the same issue. The P210 is for voltage rated. I already set 480V but it still happened.

>There is a parameter (P210 mentioned above sounds right (I
>don't have a manual handy) that identifies the system
>voltage to the drive. We've had machines come in set to 400
>instead of 480 and they tripped immediately on power-up. If
>yours is set to 440, for example, it may not trip right
>away. I would research that parameter and see what it's set

Hi Robb_EI,

I was reading your post on VFD overvolatage fault and i found this very interesting article. Here is the link if you want to troublesshoot this problem by adjusting the decelarating time ramp or other parameter to adjust:



I've had a similar issue with a V20 driving a wood chipper via a Vee belt. We adjusted the DC buss level p2172 to 1000V, and sample time p2173 to 1000ms this solved the F2 tripping.

However we discovered real the issue was slightly loose Vee belt causing a slip/grip drive action, causing the V20 to F2 trip, just sounded like a vibration.