Jeffrey W Percival
|1.1||21-Feb-2003||Add power budget|
This note presents the PFIS power and switching plan.
Table of contents:
There are 4 mechanical switches:
SALT Isolator Switch: this is the SALT-provided switch in the electrical room that applies 220V to PFIS on the payload. 220V is supplied to the PFIS PXI chassis, and to the etalon controller switches. This allows the etalons to be powered up (using the PXI chassis) long in advance of using the etalons. Ted Williams reports that the controllers like to be on for a day prior to use, to allow the electronics to settle.
This switch controls the two PFIS items that will usually be left on. The PXI chassis will always be left on (in normal usage) because cycling its power requires the PFIS computer (PCON) to be rebooted. Turning off the etalon controllers will require a day or more of settling time before use. We therefore expect that the SALT isolator switch will be left on except during maintenance periods.
PFIS Instrument Power: this switch is the PFIS "maintenance mode" switch. Whenever any invasive work is to be done on PFIS, this switch will be opened. It cuts both actuator and sensor power, but maintains power to the PXI chassis and the etalon controllers. This is also the emergency stop button.
PFIS Motor Power: this switch cuts power to the motors. Sensors and pneumatics are still enabled. This is used when motorized movement is not desired, but still allows pneumatics to hold elements in place.
PFIS Pneumatic Power: this cuts power to the pneumatic relays. Sensors and motors are still enabled.
PFIS dissipates power in two ways: steady state power (e.g. power supplies, electronics) and intermittant power (motors). Our steady-state power is all enclosed in glycol cooled enclosures. Only the intermittant power is used in the beam without cooling, and only in polarimetric modes is it used during an observation. In non-polarimetric modes, the intermittant power is used to configure the instrument prior to an observation.
Steady State Power (cooled)
PFIS will dissipate power when it is in use. The steady-state power dissipation occurs in glycol-cooled boxes.
|2 x etalon ctlr||184||Mfgr spec; measured power is about half this|
|PFIS Main Box|
|PXI Chassis||4||Data sheet|
|3 x Motion Ctlr||15|
|Power Supplies||36||15A, 24V, 90% efficiency|
|PFIS Box 1|
|4 x Drivers||9.6||estimate based on measured Oriental Motors board|
|Interlocks||1||estimate from EE|
|PFIS Box 2|
|4 x Drivers||9.6||estimate as above|
|Interlocks||1||estimate from EE|
|SAAO CCD Boxes|
|SDSU Array Ctlr||4.3|
|SDSU Pwr Supply||80|
|CCD Ion Pump Ctlr||40|
PFIS will dissipate 400 W steady-state, in 6 separate glycol-cooled boxes. The allocation to PFIS is 1.1 kW.
Intermittant Power (not cooled)
Intermittant power dissipation occurs when PFIS runs its motors. PFIS motors are not cooled. The situation is mitigated in several ways:
The exception to these statements involve polarimetric observations, where the waveplate rotation occurs during an observation, and in some situations may have quite a high duty cycle.
|Power (W)||Comment||Time (s)||# Ops/hour||Energy (J)||Average Power (W)|
|HWP Rotate||3.5||est. winding = 5V||1||900||3150||0.875|
|QWP Rotate||3.5||est. winding = 5V||1||900||3150||0.875|
|Grating Magazine||7.5||est. winding = 5V||20||1||150||0.042|
We point out that this is a worst-case mode, doing 2-waveplate high-duty cycle polarimetry. Without the polarimetry, the time averaged dissipation drops to about 0.8 W.
This analysis assumes a 1-hour exposure for a typical observation.