I was testing a chiller and noted substantial distortion in the current, but not the voltage. This chiller has a star delta starter and 60 kvar of capacitors connected at load side of the M1 contactor. The attached waveforms show the distortion level at the motor terminals, capacitor and source...
What is the proper method of connecting power factor correction capacitors to a star delta motor starter? Is there any NEC reference for this (I could not find anything in NEC 460)? The motor in question is 3 phase, 208V, about 500 HP.
I obtained voltage and current waveforms from a centrifugal chiller of about 200 HP. It was running at about 70% full load. The voltage waveform looks fine. RMS voltage for A phase is 476.4V and the peak is 664V. The current waveform for each phase is flat topped at the positive and negative...
This follows the thread "large machine resonance".
Here is where we stand: The base of the machine appears to be resonant because it is not firmly mounted on its concrete and grout base.
At first glance, this could be easily corrected by simply bolting the base in more locations. However...
I recently conducted at test of a chiller. The motor is hermetic. About 175 HP, 480V. Test at 75% load.
Vibration data showed shaft speed harmonics with 2x (not 1x) slip X #poles sidebands.
Current signature showed slip X pole sidebands 50 db down.
Current waveform shows a sinusoidal notch...
A demonstrated resonant condition exists in a gearbox. Vibration of 1"/sec is measured on the structure at 330 Hz. The gearbox is driven by a 1000 HP DC motor and runs a rolling mill. The gearbox is about 6' by 6' by 4'. It sits on a concrete foundation that reportedly extends 8 feet...
A demonstrated resonant condition exists in a gearbox. Vibration of 1"/sec is measured on the structure at 330 Hz. The gearbox is driven by a 1000 HP DC motor and runs a rolling mill. The gearbox is about 6' by 6' by 4'. It sits on a concrete foundation that reportedly extends 8 feet...
A client wants polarization index testing done on 18 motors that use Wye Delta starters. When the motor is off, the phases are not interconnected. Thus, ordinarily, each phase of the motor would be tested to ground individually. This is time consuming. I propose to place jumpers on the...
I am considering the use of surge testing in a predictive testing program. Are any of you conducting surge testing on large numbers of 480V motors? Have you experienced faults that could be blamed on the test procedure? Have you restarted motors after they have failed a surge test?
