Background: I have an old centrifugal motor pump (for big pool filtration) which works good but I am considering of buying a SINAMICS V20 to drive it for electrical cost-saving and efficiency purposes (will switch my home soon to only solar power + batteries).

My question will be about if and how I need to protect this old motor against insulation stress by using it with a VFD.

Motor has the following properties according to plate:

• 230V single phase (although I will use it as 3 phase with the VFD since it has U, V and W windings)
• Cos φ of 0.98
• H max 22.5 m.w.h
• 2590 W input rated power
• 2200 W mechanical output power
• 2880 rpm at 50Hz
• 11.5 Amps rated current.
• Manufacturing date 2016 (but sent 1 or 2 times to be coil rewinded to a local specialist)

I was thinking of buying the SINAMICS V20 Single Phase Input / 3-phase Output 6SL3210-5BB23-0UV1 rated for 13.6 Amps and 3 kW. Price is around 320 Euros.

For info, cable length between VFD and motor is around max 5 meters if not less.

With all this, do I even need to protect the motor at all? If yes what would be my options to protect it against insulator stress, since I don't know if it is fit for a VFD?

1. Is there a parameter in the VFD to make the switching time / voltage rise time slower to avoid voltage peaks? I don't care about the reactivity of the drive. I just care about a soft ramp and then a fixed speed on the pump.
2. Install motor reactor between VFD and motor?
3. Install a Sine-wave filter?
4. Install a dv/dt filter plus VPL?

For options 2, 3 and 4 I spent some time reading this Industry Mall link but was not able to deduce which one I would need.

Additionally, in terms of budget, could you tell me which one the last three options is more or less economical? Ideally I would be ready to spend not much more than 50% to 100% the price of the VFD.

Thanks in advance for your tips.

Just tossing out an idea on how to save costs.

Purchase a replacement inverter duty motor and be done with it.

For that size motor, adding the proper output filtering to protect the non-inverter duty motor that's been in use for some time will cost more (most likely) than the proper motor designed for use with VFDs. 

mm2021

Background: I have an old centrifugal motor pump (for big pool filtration) which works good but I am considering of buying a SINAMICS V20 to drive it for electrical cost-saving and efficiency purposes (will switch my home soon to only solar power + batteries).

My question will be about if and how I need to protect this old motor against insulation stress by using it with a VFD.

Motor has the following properties according to plate:

• 230V single phase (although I will use it as 3 phase with the VFD since it has U, V and W windings)
• Cos φ of 0.98
• H max 22.5 m.w.h
• 2590 W input rated power
• 2200 W mechanical output power
• 2880 rpm at 50Hz
• 11.5 Amps rated current.
• Manufacturing date 2016 (but sent 1 or 2 times to be coil rewinded to a local specialist)

I was thinking of buying the SINAMICS V20 Single Phase Input / 3-phase Output 6SL3210-5BB23-0UV1 rated for 13.6 Amps and 3 kW. Price is around 320 Euros.

For info, cable length between VFD and motor is around max 5 meters if not less.

With all this, do I even need to protect the motor at all? If yes what would be my options to protect it against insulator stress, since I don't know if it is fit for a VFD?

1. Is there a parameter in the VFD to make the switching time / voltage rise time slower to avoid voltage peaks? I don't care about the reactivity of the drive. I just care about a soft ramp and then a fixed speed on the pump.
2. Install motor reactor between VFD and motor?
3. Install a Sine-wave filter?
4. Install a dv/dt filter plus VPL?

For options 2, 3 and 4 I spent some time reading this Industry Mall link but was not able to deduce which one I would need.

Additionally, in terms of budget, could you tell me which one the last three options is more or less economical? Ideally I would be ready to spend not much more than 50% to 100% the price of the VFD.

Thanks in advance for your tips.

 

Thanks for your suggestion 0_Einstein, but I would like to keep the motor if possible. It runs fine since ages.

What about the need to protect it at all? In the end the motor will still run at 230V anyway (but 3-phase). Are the voltage spikes big enough to damage it?

You can try a sine wave filter at the output of the VFD to help smooth out the spikes. 

Yes since VFD output voltage spikes can easily reach (^√2/₂xVAC_rms) = 325VDC (PWM voltage from the VFD's DC bus). 

If the winding resistance is rated for 325V, you should be ok - for the windings.

Be aware, the motor bearings may need attention as well.  You might want to install a bearing grounding kit meant for motors connected to VFDs.  It helps prevent bearing spalling from the spiking voltages output from VFDs (see highlighted link for more details).

mm2021

Thanks for your suggestion 0_Einstein, but I would like to keep the motor if possible. It runs fine since ages.

What about the need to protect it at all? In the end the motor will still run at 230V anyway (but 3-phase). Are the voltage spikes big enough to damage it?

I would assume that the rewinding specialist used wire rated at least for 380V (probably, since I guess he would not bother to switch wires when rewinding 230V or 380V motors?).

On the other hand I totally forgot about the bearings issue indeed.

For the sine wave filter I think is way too expensive; will think about the bearing grounding kit though.

Regarding a new motor, I was blinded by looking only at the SIMOTICS GP line and its prices, when actually the FL line should cover my needs and is much more affordable (I see no difference between the two lines except for the fact that on the FL you get lower lead times at the expense of lack of fine customization, am I right?). So maybe the idea of buying a new one is not that bad anymore .

Many thanks again for your advice.

0_Einstein

You can try a sine wave filter at the output of the VFD to help smooth out the spikes. 

Yes since VFD output voltage spikes can easily reach (^√2/₂xVAC_rms) = 325VDC (PWM voltage from the VFD's DC bus). 

If the winding resistance is rated for 325V, you should be ok - for the windings.

Be aware, the motor bearings may need attention as well.  You might want to install a bearing grounding kit meant for motors connected to VFDs.  It helps prevent bearing spalling from the spiking voltages output from VFDs (see highlighted link for more details).

mm2021

Thanks for your suggestion 0_Einstein, but I would like to keep the motor if possible. It runs fine since ages.

What about the need to protect it at all? In the end the motor will still run at 230V anyway (but 3-phase). Are the voltage spikes big enough to damage it?