User`s manual

49
Magtrol WB/PB Dynamometers
Chapter 2 – Installation / Mounting
2.4 MEASURING RANGE
As with most transducers, dynamometers should be operated in the upper part of their measuring
range, between 10% and 100% of their rating.
2.5 DRAG TORQUE
Magtrol dynamometers are characterized by a low drag torque: approximately 1% of the rated torque
for WB Series Dynamometers and approximately 2% for PB Series Dynamometers. Refer to the
corresponding data sheets (see Section 1.2) for the maximum drag torque values of each model.
Drag torque (which is measured by the dynamometer) is generated by friction originating from the
bearings, the contact between the powder and the rotor unit in magnetic powder brakes, as well as
all other mechanical contacts.
2.6 TOLERATED RADIAL AND AXIAL FORCES
Note: Any radial or axial force exercised on a dynamometer causes
premature wear of the bearings, as well as an increase of the drag
torque.
The following table shows the maximum axial and radial forces the WB/PB Series Dynamometer
can support without being damaged:
Series
Standard version High-speed version (HS)*
F
axial
max [N] F
radial
max [N] F
axial
max [N] F
radial
max [N]
WB/PB 2.7
20 5 4 2.5
WB/PB 43
40 30 8 15
WB/PB 65
200 60 40 30
WB/PB 115
300 200 60 100
WB/PB 15
N/A N/A N/A N/A
* Only Eddy-current (WB) Dynamometers have, as an option, a high-speed version.
For WB-HS Dynamometers, the limit is lower in order to protect the high-performance bearings.
Magtrol offers, for the same reason, a specially adapted high-speed coupling.
By applying a radial or axial force on the dynamometer, the bearings are subjected to different
stresses. This hinders them from rotating freely and generates torque on the measuring line.
The side load of the measuring line is detected by the dynamometer cell. This is not an offset but a real
torque, normally measured. Thus, the zero on the electronics must not be set when the dynamometer
is mechanically coupled.