The Cryomagnetics Model 4G Superconducting Magnet Power Supply is an advanced, four-quadrant instrument designed for powering superconducting magnets. Its four-quadrant operation allows for smooth sweeps through zero current, facilitating hysteresis loop experiments and magnetic field reversal without the need for current reversing switches or pauses. The supply can provide both positive and negative output current, along with positive or negative voltage, enabling it to source and sink power.
The 4G is available in various configurations, utilizing one or two power modules. These modules come in 100A, 150A, and 200A units, allowing for single 100A, 150A, or 200A configurations, or a dual 100A unit. Older dual units can be externally paralleled by the user to achieve a full 200A current capability for a single load, though this requires specific operational considerations (detailed in Appendix E). All 4G units are capable of delivering up to ±10 volts of output voltage.
The device features a user-friendly menu system for setting up operating parameters, making daily operation simple and quick. A high-quality 5 1/4" color LCD provides an easy-to-read display, showing current in a large font visible from a distance.
Important Technical Specifications:
- DC Output: See model-specific specs, up to ±10 V.
- Output Power: See model-specific specs.
- Ripple and Noise: 20 µA rms, 10 mV rms @ 100A.
- Stability (drift) at 25 ± 1°C: ±3mA / °C, ±0.01% Vmax.
- Display Resolution: 0.1 mA, 1 mV.
- Display Update Rate: 2Hz.
- Output Current Granularity: 0.1 mA, 5 mV.
- Sweep Rate Resolution: 0.1 mA/sec.
- Source Effect (line regulation): 0.005% Imax, 0.05% Vmax.
- Load Effect (load regulation): 0.01% Imax, 0.01% Imax.
- Output Protection: Protected from damage due to quench.
- Persistent Switch Heater: 0-125mA, 0-12V.
- AC Input: 220-230V AC, 50-60 Hz, 9.5A max.
- Circuit Breakers: 16A, 240V AC, slow blow.
- Operating Temperature: 15 °C to 35 °C.
- Relative Humidity: 10% to 95%, non-condensing.
- Over-Temperature Protection: Unit limits discharge power to prevent overheating.
- Overall Dimensions (excluding front handles): 483 mm W X 133 mm H X 533 mm D.
- Interfaces: USB 1.1/2.0 Full-Speed, IEEE-488.2-1992 Standard, IEEE-802.3 10/100 BASE-T Ethernet.
- Shut-down Input: +5V, +24V, or switch closure signaling.
Model Specific Specifications:
- 4G-100: 100A Max Current, 1000W (10V @ 100A) Max Output Power, 29.0/13.2 lbs/kg.
- 4G-150s: 150A Max Current, 1500W (10V @ 150A) Max Output Power, 43.2/19.7 lbs/kg.
- 4G-200s: 200A Max Current, 1600W (8V @ 200A) Max Output Power, 43.2/19.7 lbs/kg.
- 4G-Dual (100/100): 100A/100A Max Current, 800W/800W (8V @ 100A) Max Output Power, 43.2/19.7 lbs/kg.
Usage Features:
- High Stability: Provides quiet, stable output power due to low noise design, precision current monitoring, and control circuits.
- Power Fail Magnet Discharge: In case of power failure, the supply automatically switches to "Power Fail" mode, discharging the magnet at a low voltage (approx. 0.7V). Upon power restoration, it displays "PASSIVE DISCHARGE" and continues slow discharge until the user intervenes. Pressing [PAUSE] stops discharge and allows recovery.
- Independent Upper and Lower Current Limit Setpoints: Allows sweeping between two setpoints without re-entering menus.
- PID-Controlled Sweeping: Internal PID control circuits ensure smooth sweeping between setpoints without requiring magnet voltage taps.
- Adjustable Settings During Sweep: Parameters can be changed via the menu system at any time during operation, with the display continuously updating the supply/magnet status.
- Computer Interfacing: Standard USB and IEEE-488 interfaces offer a comprehensive set of monitor and control commands. Ethernet interface is also available. LabVIEW™ drivers are provided.
- Persistent Switch Heater Supply: A built-in supply for persistent switches.
- Remote Shut-down Input: Allows an external signal (e.g., low helium level) to trigger magnet discharge and lock out operation.
- Quench Detection and Protection: Fully protected from quench damage. If a quench is detected, "QUENCH DETECTED" is displayed, an audible alarm sounds (if enabled), and power is removed from the output. Current readings leading up to the quench can be displayed. Quench detection must be disabled for automatic recovery from abnormal conditions.
- Setting Magnet Parameters: Users can configure magnet-specific parameters such as Persistent Heater Presence, Persistent Mode Current, Maximum Current Rating, Gauss/Amp Ratio, Persistent Switch Heater current, Quench Detection, and Inductance.
- Setting Charge Rates: Up to five different charge rates can be set for different current ranges, plus a fast rate, allowing for slower sweeps in sensitive ranges.
- Setting Limits: Users can set upper and lower current limits for sweeps, as well as voltage limits. Alarm HI/LO Limits can be configured with optional relay outputs and autoreset functionality.
- Energizing the Magnet: Step-by-step procedure for energizing the magnet, including persistent switch heater control and sweeping to desired current limits.
- Discharging the Magnet: Procedure for discharging a magnet from persistent mode, including re-energizing the persistent switch heater and sweeping current to zero.
- Fast Sweeping: Available under specific conditions (persistent heater present and OFF) for rapid current changes.
- Shim Supply Option (Appendix G): Controls up to 12 independent superconducting shim coils in addition to the main magnet. Features include 12 persistent switch heater output channels, polarity selection for multiplexing, 0-100mA heater current range, +/- 30 amp output current range, automatic shim dumping during main coil energizing/discharging, and independent shim heater enable/disable. The 4G uses its main current outputs for shim coil current, software-limited in shim mode. Periodic dumping of induced current in shim coils is performed during main coil operation to prevent quenches.
Maintenance Features:
- Periodic Inspection: The 4G should be periodically inspected to ensure secure connections, proper fan operation, and clear ventilation openings.
- Cleaning: If cleaning is required, disconnect the power cord and use a soft cloth dampened with water.
- No User Serviceable Parts: The unit does not contain user-serviceable parts. Repairs require factory authorization and return to the factory to maintain integrity.
- Firmware Upgrading (Appendix F): Provides instructions for upgrading main operating firmware and/or power module firmware using Flashit programming software and FTDI virtual COM port drivers.
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