Line Reactors for Harmonics Reduction

Is this really due to harmonics or could it be due to either capacitive inrush current or just plain normal operation of the CT-SCAN UNIT (as a line reactor won't really help with these problems).

Do you have a manual with electrical specifications you could refer to?

Sori no Manual from manufacturer. Thanks for your comments. Happy day!

contact the manufacturer.

Sir, this is a big problem for us since we experience frequent damage ( twice a year) in the G.E. CT-SCAN power supply cards. According to our G.E. technician this is abnormal for this type of equipment. By using a clamp ammeter the normal running current is 80 Amp. but it will suddenly peak at 180 Amp. in a split second then back to normal. This is observed everytime it will scan the patient.Presently we already installed protection relays in its source (phase loss, over/under voltage and over/under current). What I want to know where is the source of this problem from the power source or internal to the equipment?

According to our G.E. technician this is abnormal for this type of equipment.

This really sounds like the manufacturer's problem that they need to fix, adding additional protection equipment yourself to fix something damaged or faulty inside the CT-SCAN is like trying to modify how a computer switch mode power supply works - you may be able to but chances are greater you will cause more damage and void the warranty.

These are good observations and nicely explained.

• Does this observed behavior occur frequently/all the time
  
• Is this observable over the space of an hour, minutes, seconds, days,weeks, months? Mean time between events?
  
• Is there a correlation between the progress of the scan procedure and the observed spike?
  
• When the current spike is detected what is the incoming line voltage doing? Dipping or spiking?

Have you physically walked the incoming line route to be absolutely sure that it is connected directly and exclusively to the utility supply? (there has to be reason why this was a requirement)

Yes sir, i already checked the exclusiveness of the supply in fact it has its own monthly billing.The voltage line to line during the scanning process is at steady state only the line currents changes or spikes. Thanks for the very informative comments!!

Line to line? You mean Line to neutral yes? or is this polyphase?

Yes, a three Phase system. line to line no voltage line to ground

You need to check current on all phases and the LN (not LG) voltages on each as well.

What is your location?

The last time I used a reactor was to limit fault current. Nothing to do with harmonics.

As soon as you introduce an iron core you are going to get inrush. Motors, transformers etc - its what happens.

You really need to do an analysis and find exactly what harmonics you have.

From memory I don't think the harmonics get from the secondary to the primary side of the Tx.

Can you please describe that supply transformer circuit in a little more detail? Is this a step-up transformer or a dual coil type (dual primary for 220 or 440 volt connection)?

Are you sure your current clamp is not opening while you are taking measurements?

Do you have an MRI (magnetic resonance imager) in the area?

Sir, this is a step-up transformer since our utlility standard voltage is 220V that is why we need to step-up the voltage to 440V since our equipment came from the U.S. We dont have any MRI in our hospital and this equipment has a dedicated power supplty direrctly from the utility as required by our equipment supplier. Aside from clamp ammeterwe already installed a power monitoring unit (PM 700).

A line reactor increases grid impedance, and is NOT advisable unless you know equipment power supply specifics, since it could cause serious problems if incompatible. And I wouldn't risk responsibility of ANY servicing or mods on a possibly damaged equipment that could cause EXTREME health hazards if miss-operated etc, without detailed manufacturer instructions AND clearance. S.M.

if u try surge suppressor( operates in nano seconds) in secondary, it will open the circuit. the only botheration is u have to switch it on again.

Disconnect the primary leads to the HV transformer. Now try for a scan. This will allow you to see if the mechanical or HV is causing the current spike. If the current still spikes, the gantry drive motor and associated circuits and equipment are doing it. You might have a place in the gantry rotation where it almost sticks, spiking current demand.

Sir, what is the primary leads to the HV transformer? Can we run the scanner without them? Sori cannot get the message clearly.

You are not going to be getting scans, but opening the primary leads to the HV transformer takes that load out of the situation. If you still get the power surge when you operate the scanner, the problem is in the mechanicals, not the X-ray generation.

Thanks, clear now. i will try.