Can a difference in phase voltages cause a motor to fail?

[RogerMorris]

Thanks very much for your comments and knowledge, it is rural Spain and I have since discovered that phase imbalance is not unusual.
The motor is a Grundfos 3VC 2.2kw and it is connected via a PROBD21P Digital Pro Pump Relay which as I understand it will cut the motor if the current is either too high of too low but not react to phase imbalance

 

[RogerMorris]

MS 402

Submersible motors

product-selection.grundfos.com

Avel - electronica,lda

Electric control boxes and electronic relays for water pumping systems

www.avel.eu

 

[pc1966]

Can you (safely) measure the phase-phase voltages? They ought to be around 415V here.

Most likely the motor is connected only to the 3 phases, and not neutral, so an offset/imbalance in the neutral is much less of an issue.

Worth having as much information as possible in case of any dispute over the motor problem, though it still seems likely the supply is a problem.

 

[RogerMorris]

Yes the motor is only connected to the 3 phases not neutral and the voltages are now

L1 247v
L2 241v
L3 236v

L1-L2 421v
L2-L3 415v
L1-L3 422v

 

[Darkwood]

I would be looking at setting up a system that give extra monitoring, protection from voltage irregularities and redundancy.
I did a 2 pump system that usually runs each pump alternatively for drains and sewage but under exceptional circumstances (heavy rain) the level sensor will trigger both pumps for fast evac' and is monitored for overtemp, overcurrent, short circuit and earth leakage on each motor, a PLC program will recognise any condition raised, swap the program to 1 pump operation and raise the alarm, it has been running 3 yrs now no issues thus far, the previous system cost them 5k in call outs and tank emptyings one yr so already the investment has paid.
The above would probably push you for 2k to 3k (£) or if you really want to pull out all the stops then fitting VSD's and giving extra protection from clogging and stalling with anti-rag software adding another 1k to the pot...
Depends on your pocket, the size of the holding tank and the cost of failure to inconvenience and business if applicable.

As you have voltage issues I didn't have then your scenario would need extra to ensure you can reduce or eliminate the effects of voltage imbalance.

 

[RogerMorris]

Thanks for the advice darkwood.

It has been suggested that I cut my losses with the 3 phase approach and install a single phase motor.
What are the downsides of that idea?

 

[stevethesparks]

Would a single phase to 3 phase vsd not be feasible?

 

[pc1966]

Yes the motor is only connected to the 3 phases not neutral and the voltages are now

L1 247v
L2 241v
L3 236v

L1-L2 421v
L2-L3 415v
L1-L3 422v

That on-line calculator is now saying:

• Average Voltage: 419.33
• Voltage Imbalance: 1.03%
• Motor Temp Increase: 2.14%

It is advisable to decrease imbalance to below 1% if possible​

 

[RogerMorris]

Do you mean something like this

Single phase input, Three phase output VFD | ATO.com

www.ato.com

 

[pc1966]

So that particular measurement is not really looking a very likely reason for failure, but your L-N voltages look more balanced now as well so there might be some significant fluctuations in the supply balance.