Safety Interlocks - EBARA A70W Instruction Manual

(IV)
Appendix 2

Safety Interlocks

In compliance with SEMI S2, Safety Guidelines for Semiconductor Manufacturing Equipment,
EBARA A Dry Vacuum pumps include a set of safety interlocks, which shut down the pump
upon detecting a violation of "safe" condition.
The following interlocks are standard equipment on all A Series Pumps:
Emergency Off (EMO): A manually activated button breaks a low-voltage control circuit that,
in turn, interrupts line power. Restarting the pump(s) requires a manual reset of the
twist-lock button. Design implementation of this important interlock can take diverse forms
based on process tool specifications and fab electrical distribution. Typical variations
include:
Pump-only EMO: A button, mounted on or near the pump, controls activating power to the
pump motor starter relay(s). Activation interrupts all electrical energy beyond the pump
control panel.
Tool EMO: A button, included in an interface panel, connects in series ("daisy chain") with a
set of EMO buttons. Activating any of the buttons de-energizes contactor coils in the tool
distribution panel and interrupts power to the process tool and its ancillary equipment,
including the pump(s).
Gang EMO: A button, mounted near a set of pumps, controls power to the coil of a contactor
feeding a distribution panel. Activation cuts power to the entire panel.
Nitrogen Flow Low
A flow sensor trips when nitrogen supply to the pump (oil bearing(s) and inter-stage injection)
drops below its factory set point, opening the motor starter relay(s) and shutting down the
pump. Restoration of sufficient nitrogen flow permits restarting the pump.
Motor Overload
Motor overload relays protect the pump motor(s) from overheating due to extended current
draws in excess of the motor rating without tripping due to current transients such as start up
inrush current. Current (for each phase of line power) passing through a coil heats a
bimetallic element simulating motor heating under load. Under a persistent overload
condition, differential expansion of the bimetallic element opens a contact, which interrupts
the motor run circuit. A brief cool down interval permits restarting the pump.
Overcurrent Protection
The nearly instantaneous current rise from a line-to-line or line-to-ground short very rapidly
heats a thermal element in the circuit breaker, opening of a snap action switch and
interrupting all power to the electrical panel. Manual reset, which requires clearing the fault
condition, is necessary before restarting the pump. The circuit breaker also serves as a
lockable interrupt device for servicing the pump system.
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