DC Bus voltage on VF0??

[DomB]

Hi,
Anyone know what the DC bus voltage should be on the Diagnostics page on a VF0. I guess it is the same as other VF mills also.

Mine says 330V But is quickly flickering up and down a couple of volts a bit like the spindle load reading does, is this normal.

Thanks

[Geof]

It does depend on the age of the machine. Anything newer than around 1998 (I think) it should be between 320 and 340. This depends on the incoming supply voltage and there are transformer taps that can be moved for different supply voltages at the bottom of the control cabinet.

The DC voltage does flicker around a bit and when the machine is accelerating it will drop quite a lot or deccelerating it will go high. If it drops below around 280 volts during acceleration the machine will alarm, there is a parameter and time limit for low voltage. During deccelration if it goes to high because the regen resistors have not kicked in or something it will also alarm.

Running with the DC voltage always near the high limit might give regen overheat alarms if the machine is doing a lot of starting and stopping; running with the voltage low may give spindle overheat alarms under the same conditions.

If your incoming supply is a bit limited in its peak capacity the low voltage alarm may occur frequently. This will happen especially if you overlap spindle acceleration to maximum speed at the same time all the axes are run from the tool change position to the start point for a cycle; this puts the maximum draw on the DC bus because there are four motors pulling maximum power. If this happens the fix is to separate spindle acceleration from axis movement or drop the spindle acceleration slightly; there is a parameter for this.

[DomB]

Hi,

The supply to the building is massive.

But the voltage in I measured as 418V, but the Haas techie hooked it up to the 457-429V taps, which would obviously give a lower output when fed with 418V, and the regulator could be maxing out to keep the voltage at 330V with no ripple smoothing left over.

I would have thought the 428-403 tap would have been better. When he connected it he was trying both taps as he said the voltage was a little close to the higher end that day.

Should i move the tap back.
Dom

[Geof]

Hi,

The supply to the building is massive.

But the voltage in I measured as 418V, but the Haas techie hooked it up to the 457-429V taps, which would obviously give a lower output when fed with 418V, and the regulator could be maxing out to keep the voltage at 330V with no ripple smoothing left over.

I would have thought the 428-403 tap would have been better. When he connected it he was trying both taps as he said the voltage was a little close to the higher end that day.

Should i move the tap back.
Dom

You measure 330 when the machine is not running so that should be okay. To my knowledge there is no regulation in the machine that controls the voltage of the DC bus. It is simply the three phase bridge rectified voltage from the incoming supply; there is also very little capacitative smoothing.

When the machine was connected maybe the incoming supply was running higher. Have you checked it on different days and at different times during the day? You have an on board transformer (I think) because the Haas machines are made for 208 to 240 on the incoming supply and yours is nominally 440. However, line voltage can easily fluctuate +/- 5%, sometimes more so this gives you a range of 418 to 462 on the incoming supply.

If there are no having problems running the machine I would not worry but you may want to get some more opinions.