Hall D Solenoid: Voltage Spikes in Coil 2
Lats updated: 20 Jan 2017 by gen@jlab.org
Voltage spikes have been observed in coil 2 at fast changes of the field.
Such spikes often happen at the starts of the fast dumps. Sometimes they happen
at the regular current ramping. Fast (a few ms), 10-50V spikes happen in the subcoil
2D (the one supported by the added buttresses). In December 2016 slower (hundreds of ms)
and smaller spikes tripped the magnet at ramping up.
Trips during ramping up in December 2016
On Dec 13-14 the magnet tripped 3 times at the regular ramping rates.
The Quench Detector was triggered by voltage excursions in Coil 2.
- 2016/12/13 17:41:26 Trip at 740A, 0.2A/s, See LOG 3446267
- Broad picture The QD was triggered by a positive voltage excursion on Coil 2 started at 17:41:26.4.
The power supply turned off at 17:41:26.65 and the dump resistor was engaged at 17:41:27.08.
The dump was followed by a sharp negative voltage spike on 2D (vtt7) at 17:41:27.1.
See the signals in
a wide time-range plots, and
a narrower time-range plots.
- The voltage excursion The voltage excursion which lead to the trip is shown
here. The voltage
went up by 0.3V on vtt7 (2D) and by 0.1V on vtt4-6. All other subcoils show similar, but negative
excursions of 0.05-0.10V. Similar pulses occurred on the pickup coils: the pickup coil pc2d produced
a pulse of about 25mV on the level of 20mV caused by the ramping (0.2A/s). All this indicates that
the pulse is rather caused by a redistribution of the magnetic field (becomes higher around Coil 2
and lower elsewhere) than a resistive component in one of the subcoils. The pulse reaches maximum
in about 0.2s, and then decreases with a similar slope.
- A sharp negative spike at the dump At the beginning of the dump, at 17:41:27.108
a sharp (<1ms) -30V spike happened in 2D (vtt7, vtt7b), shown
here.
Such spikes during dumps have already happened a dozen of times during our operations.
The spike also produced
a sharp mechanical signal in the 2-top accelerometer (Coil 2, top).
- 2016/12/13 19:37:15 Trip at 505A, 0.2A/s, See LOG 3446295
- Broad picture The QD was triggered by a positive voltage excursion on Coil 2,
similar to the previous one at 17:41:26, started at at 19:37:15.4. In about 80ms the
voltage on 2D (vtt7) increased by 0.15V, and about 4V on the QD. At 19:37:15.486 a sharp
positive spike happened on 2D (similar to the spike during the previous trip),
which triggered the QD.
See the signals in
a wide time range.
- The voltage excursion The voltage excursion is shown
here.
- A sharp positive spike , see a zoomed area
here and
here .
The <1ms spikes are about +20V on 2D and -10V on Coil 4.
The spike also produced
a sharp mechanical signal in the 2-top accelerometer (Coil 2, top).
- 2016/12/14 09:31:50 Trip at 1150A, 0.06A/s, See LOG 3446544
Very similar to the trip on 2016/12/13 17:41:26, see the plots
here and
here , but
without a spike at the dump. The voltage excursion on 2D reached +0.3V and went down.
Other trips and spikes in Coil #2
- 2016/03/28 09:03:30 Trip at 510A, 0.2A/s, See LOG 3392805
- Broad picture The QD was triggered by a small, ≈2 s negative
voltage excursion on Coil 2 started at 09:03:26. The QD was triggered barely, while the excursion
started decreasing. About 0.15 s after the start of dump a sharp voltage
spike on the subcoil 2D happened (as it often happens at the beginning of dumps).
The sign of the voltage excursion was opposite to the sign of the excursion
which tripped the magnet in December 2016.
There are various
plots in:
here,
here,
here,
here
- 2017/02/07 13:58:10 Trip at 1350A, 0A/s, See LOG 3456545
caused by accidental pushing the crash button in the refrigerator building. During the initial
phase of the dump (at -10V at the magnet) the typical ≈ -30V spike happened on the VTT7. The spike
had an internal structure of 3 ≈1ms sharp spikes. After the dump resistor was engaged,
several sharp spikes followed, producing also signals in the accelerometer.
There are various
plots in:
here,
here,
here,