Voltage Suits Up

How does it "suit up"? In Adidas or Reebok or Nike or other?

I mean the voltage increased once the load was connected.

Then that could be "shoots up."

Thanks for the correction. How to correct in the question now?

Kindly read it as Voltage Shoots up instead suits. Sorry for the speeling mistake

When you say the voltage 'shoots up' are you simply measuring peak values, or monitoring the waveform?

You could be seeing inductive spikes during load variations rather than increased line voltage.

Have a look with a suitably rated CRO and probes to see what is really happening.

What is the type of machine ?

hope it is a 3 phase induction motor. hp ?

normally a voltage drop when there is a load applied on motor , because of increase in current.

Is this rise in voltage is instantaneous or it lasts till the end of cutting process ?

Thanks for your kind response.

Yes it is 3 phase induction motors. 5 KW

Some times instantanious and most of the times till end of the process.

There are sequence of operations involved with various capacity of motors like 1 HP, 3 HP and 7 HP.

It is not rise only particular motor's operation. It rises at different motor's operations.

I suspect that what you're seeing is an artifact of how the voltage is being measured, not a real increase in the peak voltage in the AC power cycle. Are you viewing the actual wave form on a scope, or using an instrument that integrates the wave form and displays something like an RMS value? And what are the points that you're measuring between? It may be that what you're thinking of as the "ground" reference may be affected by whether the motor is on or off. If so, you could conceivably have a hazardous wiring situation.

It's hard to say anything definite without a lot more information. However, what you're reporting is definitely anomalous. Something's wrong, and you need to resolve what it is.

is the power is from a DG set or it from EB ?

if it is from Dg , may be it is from Dg. when apply load dg rpm shoots up.

what is the Dg kVA

Thanks. The power is frmo EB as well as DG.

DG is 500KVA.

Same kind of machines running without any problem. Kindly advice.

What is the voltage rating of the motor(s) that drive(s) the machine? What does the rating plate say?

380 V - 3 phase

What has caused this phenomenon to be noticed? Why has the concern arisen?

The Emergency circuit activated. So we checked the voltage and noticed this.

Is it happens both with EB(utility) and DG supply ?

Does the equipment work satisfactorily despite this phenomenon?

Phase sequence relay has gone damaged after this problem.

Do you have Power Factor Correction Capacitors on the AC motors by any chance? If so, and they are sized for a loaded motor, until the load engages you will be over correcting, which can raise (suit up ) your voltage measurement.

No such or any other capacitors are in this circuit.

Dear Mr.tsmoorthy,

It appears to me from your statement - "the Voltage shoots up" when load is put on.

What is the type of load - you have not mentioned. My opinion is the your Load should be Capacitance dominated load or more capacitor bank is in the circuit - which will result in a higher TERMINAL VOLTAGE, than the INDUCED VOLTAGE of the Power Source, be it Grid Power or Diesel Generator.

Let us see the comments from other CR4 MEMBERS.

Thanks,

DHAYANANDHAN.S

Yes it is SHOOTS Up. (Is it posible to correct the spelling now??)

The type of load is just a cutting machine with Induction motors. It happens in both the supply sources.

this is the first time in my experience i heared, by connecting the load voltage boots up to 380V to 420V. as u mentioned the application is for cutting machine, the voltage never boots up by connecting normal induction motor for cutting applications, may be the motor getting over excitation due to changing the motor properties, due to over excitation only we can see voltage boots up, normally happens when we connect "synchronous motor" for power factor improvemnets.

thanks

OH, my poor English language, what has become of you?

I suspect if DG, the DG cannot react quickly enough to the starting of your motor(s) in various locations, resulting in AVC circuit overshooting, and if trouble with AVC, then it will fail to regulate back down after the current surge. One of the posters mentioned (most accurately) that capacitive load during motor switch-on is high, and this results in a surge of current. If your supply is from the grid, there may be an undersized transformer in the works. Just IMHO (in my humble opinion). You should consult with your equiment supplier as to the exact electrical requirements, and consult with your local power company as to your transformer output characteristics. Likewise consult with the manufacturer of your DG, about how to maintain it in a ready state, for example some small constant load (some lighting perhaps) might be used to help the problem...?

It happens both with Grid and DG.

Already the machine was running wihtout any such issues with the same sources. But recently got this problem. It is not just 420, but some instants it goes to 480 or more, but just for a while.

Its within the system. Not from out side. You have to investigate one by one. I have come across voltage going down as ampere shoots up as in motor starting or similar cases. Check what change you made on the machines before and after these phenomena.

We have checked the complete wiring inside the machine, power supply and swaped the Stabiliser, but still we are getting this issue and really not able to find the solution or the reason.

"Phase sequence relay got damaged " . This gives me some clues ...

please go behind this - phase sequence

We feel that due to this problem that relay may damaged. The machine will not start if the phase sequence changed.

Thanks a lot for your continuoues tips