Pump Performance - Voltage Drop

Dear JRaef,

Firstly, I hoenestly thank you for your prompt reply. Ok I will check the drives again that any torque limit have been set. All drives are set for 400V and 50Hz,anyway I would conform it back that any setting have been left. But it cant be a capacitor issue since all the drives are the same as you said. Actually there are several modes in the drive namely,

1. V/F 2 points

2. V/F 5 point

3. V/F quad

4. Evergy save

5. syncrounous

presently the drives have been selected to V/F quad since it has been recommended for pump application where got variable torque. However I have tried, 1, 3 and 4 above, but the result still the same. Please let me know if there could be any impact from the motor class for this issue.

To clearly identify the problem, please check the followings -

1. Remove the motor cable connections at the drive end. Run the drive in this condition. Do you face the same problem? If yes, the problem lies with the basic parameterisation of the drive.

2. If no, then this is happening after connecting the motor. Then this can be due to the voltage drop on the cable. Is the motor cable length too long?

I have not tried that option, but it is unlikely to happen such a voltage drop due to cable, beside the cable length maximum 25m and cable is 95sqmm as well. Anyway I can try that also. But please note, moment the motor started, the incoming voltage shown in the drive HMI decreases 400V to 374V something regardless of the set frequency. However when the incoming voltage measured, it is acceptable around 399V - 400V. I have checked the set parameters thouroughly but nothing wrong with the set parameters, and it was confirmed by the supplier as well. Are these drives capable of delivering 400V at 50Hz (Theoretically it should be able to deliver same voltage as supply voltage right? )

Try the below we recently commissioned the same kind of VFD: Make factory setting first. 2. Simple start page side set Motor parameters as per Motor name plate. Make Autotuning - Yes Low speed - 0Hz, High speed - 60Hz. 3. Input/Output configuration page side set LI1 - forward AI2-(current, min.,- 4ma & max., - 20ma) AO1 - (motor frequency, min., - 4ma & max., - 20ma) 4. Command page side set, Ref channel1- AI2 Ref switching 2 - channel1active 5. Application Function page set, Preset speed page - 2 preset speed - LI5 2preset speed - (0 to 60Hz) whatever frequency you need set it. when, L/R switch position is Local you will give start command from field side only at the time VFD will run preset speed. stop condition VFD will stop normally. when, L/R switch position is Remote you will give start command from DCS only. at the time VFD will run DCS analog signal(4 - 20ma) ref., speed. stop condition VFD will stop normally. when VFD will give trip command or Emergency push button press, at the time only KM1 contactor will deaneries.

All the parameters are set as you have mentioned here. But this preset speed setting I am not so sure and have to check. Kindly tell me, haven't you experienced similar issue there. I meant have you checked the VSD output voltage at 50Hz (or 60Hz ) ?

We didn't face any problem there, it was a 60Hz system used.

What is relation between load and voltage - at the lowest load the same 370V? (Maybe the drives are undersized)