doble TDR9000, User Manual, Page: 258 / 454

Test Plan Items
A-58 72A-1898 Rev. A 11/01
Monday
, November 26, 2001 1:09 pm
Transfer Function In most Bulk Oil Circuit Breakers, the transducer connecting rod is
connected to the moving contact assembly through the operating rod.
Thus, the contact movement and the transducer connecting rod
movement are essentially identical.
Advances in circuit breaker design have resulted in many new types of
circuit breakers. In many of these circuit breakers, it is not possible to
attach a transducer connecting rod to a part of the circuit breaker
mechanism whose movement is identical to the movement of the Main
Contacts. However, it should be possible to connect it to a mechanism
whose motion (secondary motion) has a relationship to the Main
Contacts. This relationship or
Transfer Function, when applied to the
secondary motion, allows the Instrument to see Main Contact motion
(primary motion).
The Transfer Function is where numbers relating the transducer
connecting rod travel to the Main Contact travel are entered, when they
are not the same. The Transfer Function acts on the following quantities:
Total Travel, Overtravel, Rebound, Contact Wipe, and Velocity, to
produce measurements for the Main Contacts that can be compared to
circuit breaker specifications.
Figure A.69 shows an example of linear to linear Transfer Function.
Figure A.69 Transfer Function
In this example, the Instrument has to multiply all travel data by 2 to
come up with measurements related to the Main Contacts.
Keep in mind that the value of the Transfer Function affects the resolution
of the measurement.
Example: If the transducer connecting rod moves 10", these 10" are
measured with the resolution 0.00125" (according to the transducer
specification).
N
OTE
Resolution is the smallest change in the characteristic being measured
which can unambiguously be detected in a measurement process.