Bass is a current regulated device. Its current can be controlled from 1-500 A in 1 A steps. A key feature of the design is low latency current commutation. The current waveform can be generated internally by a downloaded profile or by external trigger via fiber optics. Latency is typically around 5-7 microseconds.
At the start of operation, Bass performs a field tune to set its control loop parameters for the characteristics of the load. This is to enable the current rise-time to be optimised. Resistive loads can be commutated at 48 Hz and high current, highly inductive loads, around 25-35 Hz.
Current is steered via an SCR bridge. A comprehensive control scheme is employed to ensure no destructive shoot-through occurs.
The design is double insulated, with current monitoring between the “middle” earth and the external earth stake.
Over-current shutdown is via software but with an independent hardware shutdown operating in parallel.
There are internal bleed resistors for the dc link capacitors but there is also a software controlled discharge function whereby the capacitors are discharged and the energy dissipated internally.
There is an emergency stop which operates via a passive attenuator in an external fiber optic loop.
Temperature is monitored at many points internally and abnormal measurements will result in cessation of output until the temperature is safe.
Power input to Bass is via up to three (depending on load resistance), 3 phase 480V isolated supplies. The isolation must be good to 2,800V.
Main control of Bass is via its internal WiFi access point and built in web-server. However, there is also a fiber optic auxiliary communication port, where much information on internal operation can be monitored along with calibration and software updates.
Bass is designed to operate at 2000V, 400A @ 47 degC. Maximum current at lower temperatures is 500A dc.
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