User`s manual

48
Magtrol WB/PB DynamometersChapter 2 – Installation / Mounting
2.3 COUPLINGS
The dynamometer couplings used with the motor under test is an important factor to take into
consideration. In fact, a coupling which is not correctly specified for the application will lead to
measuring errors and premature wear of the dynamometer.
Given the fact that the dynamometer is a precision measuring device, high quality couplings should
be used. Couplings with insufficient torsion stiffness will generate unwanted sinusoidal signals on
the original measuring signal.
The coupling must be dynamically balanced (Q1 for WB Series Dynamometers and Q2.5 for PB
Series Dynamometers). This balancing must compensate for maximum tolerated misalignment
between the motor under test and the dynamometer. For all Magtrol WB/PB Series Dynamometers,
it is advisable to employ a twin (dual disc) coupling clamped onto the shaft keys (as shown in the
figure below).
Figure 2–6 Couplings Using Key Clamping
By using this method, no slipping will damage the coupling or the dynamometer shaft. With small
dynamometers such as the WB/PB 2.7 and 43 Series Dynamometers, mounting takes place by
tightening onto a smooth shaft, or using a self-centering coupling with two tightening screws.
Couplings must dampen axial and radial vibration and isolate the dynamometer from vibrations
generated by the tested unit, particularly in case of gas engines. With high-speed Eddy-current
(WB-HS) Dynamometers, consult your Magtrol representative for the best suited coupling for your
specific application.
Note: With more than 50 years of experience in the field of motor
testing, Magtrol is your best partner to determine the best suited
dynamometer for any given application.