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3 Axpert MKS running in 3 phase mode, a 3 phase generator and a lift


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Good day to everyone 

I have a problem that maybe someone can assist with 

I installed 3 x 5kw MKS inverters running in 3 phase mode and 30kwh of storage. Which seems to be working fine 

The 3 phase was installed primarily to run a lift in the house which is 5 stories high. But the lift failed to operate. The lights come on but no other response.

I assumed that the lift was faulty as it has not run for 9 years previous and as all other levels of the house had power I waited for the owner to get it serviced.

We decided to add a 3 phase backup generator. Upon comittioning and running through the inverters on bypass mode. Suddenly the lift burst into life and operated perfectly.

as soon as the generator turned off. The lift returned to a non operation state. 

Inverters  show no errors at all. We have also tried nutral to earth bonding which made no difference. 

Any help would be happily received 

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38 minutes ago, vlcsas said:

as soon as the generator turned off. The lift returned to a non operation state. 

What power is the lift motor?

What sort of controller does it have? If it's phase control, the inverters may not like it. Even if it's a 3-phase rectifier followed by a DC-3phase AC inverter, the current waveform won't be quite sinusoidal (≈6% ripple), which the inverters may not like.

But it sounds like the lift controller doesn't like the inverter's 400 VAC output. What voltage is the generator? Maybe you just need to switch the three inverters to 240 VAC output (240 V line to neutral, 415 V phase to phase); they default to 230 V L-N (400 V P-P).

Are all the inverters' AC-out neutrals connected together? My guess is that the controller doesn't connect to neutral at all, and if the neutral outputs aren't connected to each other, the inverters can't "push" against each other. Except when the generator is connected, the commoned AC-in neutrals will connect the AC-out neutrals.

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Hi Coulomb 

Thank you for coming back to me.

The lift motor is 2.9KW 

The Axperts are configured as phase 1,2,3 and in the matched breakers points in the breaker box. 

All Neutrals are linked across the inverters so all bonded. 

The inverters are locked to 230v and cant see anyway to change that.

The generator is matched to  230v as well.

We measured the voltages across the all phases with the inverters only and then the generator on and the phases all measure the same (say within a couple of volts)

The lift control is a massive great big unit but I dont have full details about it with me at the moment.

We tried neutral to earth bonding which made no difference.

I feel it must be a phase issue but im at a loss at the moment 

Best Regards 

 

 

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15 hours ago, vlcsas said:

We measured the voltages across the all phases with the inverters only and then the generator on and the phases all measure the same (say within a couple of volts)

Did you measure each phase with respect to neutral, or phase to phase? You should measure close to 400V phase to phase (check all three pairs of phases) if the inverters are spacing their outputs 120° apart as they should. If you had say a P1 and two P2s (no P3), then one of the 3 pairs of phases would read near zero volts. When 3 phase rectified, this might produce less than the expected 560V, and that might cause the lift controller to refuse to work. Or maybe the bus voltage would dip too far and fast under load, and/or the ripple would be excessive.

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  • 2 weeks later...

 

this is a tricky one. First determine whether the 3-phase motor is directly fed from the line by a smooth starting provision or if it is variable speed controlled by an electronic variable frequency control. In the first case check if the phase sequence is correct. You may change the sequence by interchanging two of the 3 phases at the inverters connection to the system. Or you may change the phase attributions of the inverters to P3-P2-P1 instead of P1-P2-P3 in program 28. 

In the second case the phase sequence should not matter.

If it is a ripple problem you might solve it by connecting capacitors on each phase to neutral. The capacitors must withstand at least 350V AC.

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