American Magnetics Current Leads for Cryogenic Systems Brochure - Manual (Page 2)

APPLICATION CONSIDERATIONS
VOLTAGE DIFFERENTIAL
AMI leads operate with a voltage
differential of less than 100 mV as
measured from the top of the lead to
the bottom, or 200 mV measured
between the leads on the warm end.
Upon request, voltage tap attachment
points can be provided on all lead
sizes. The measurement of this value
can be a useful tool for detecting
insufficient gas flow or an overcurrent
condition. System trigger points can
be established to take corrective
action or shut down the system prior
to overheating of the leads for
whatever reason.
PRESSURE DIFFERENTIAL
A typical pressure differential of
approximately 2 mm mercury (0.03
psi) is developed through the leads
when operating at their maximum
rated current for standard lead
lengths.
ICING & FROSTING
Depending upon the operating
conditions of the cryogenic system,
frosting or icing on or around the top
of the current lead may be observed.
This may be caused by forcing more
cold gas through the leads than is
necessary. A common example of this occurs when the background dewar boil-off gas is vented through
the leads while in standby mode. Although small amounts of icing or moisture do not generally present a
problem, AMI can provide electrical heaters to keep the exposed lead above the freezing point. Special
construction techniques are also available to prevent O-rings from freezing on the cryostat mounting
flanges.
CUSTOM INTERFACES
A number of different style interface points are available on current leads. The standard horizontal upper
end tab can be rotated to the vertical ‘Flag’ position in cases where the leads must be mounted very close
together. The warm end connection for power cables can be configured with special bolt patterns, large
surface area mounting surfaces for low contact resistance, or designed for a circular clamping type
connection. Cold end connections are also highly adaptable to suit specific requirements.
Figure 1: Dimensional References for Standard Vapor Cooled Leads Up to 10,000
Amperes