25
OPERA
TION
4. Testing
4.1
testing Considerations
A number of factors must be taken into consideration before running a test including safety, accuracy,
power dissipation, fixturing, couplings, windage, friction, vibration, cogging, eddy currents and
temperature rise. The following sections describe these factors, and their effects, in further detail.
4.1.1
S
afeTy
for general safety considerations, please follow these few common-sense rules:
• Be sure that your coupling is adequately rated for the speed and torque that you intend to
run.
• Make sure all rotating elements are covered.
• Always wear safety glasses when working around dynamometer test equipment.
• Do not wear loose clothing or ties when working around dynamometer test equipment.
• Never allow anyone to stand close to the side of, or lean over, a rotating shaft coupling.
• Insulate electrical (internal and external) motor connections.
C
aution
:
a
power
-
line
fault
into
the
dynamometer
frame
Could
pass
a
transient
surge
through
all
interConneCted
instruments
,
any
Computer
in
use
or
operating
personnel
with
dangerous
and
Costly
ConsequenCes
!
• Always connect the motor frame to a high current capacity (water pipe) earth ground.
• Be sure the motor control circuit breakers cannot be bypassed by accident. Variable auto-
transformers are especially hazardous!
• When operating dynamometers with blowers, hearing protection must be worn.
4.1.2
a
CCuraCy
Following, is a list of several factors that affect the apparent accuracy of the torque readout.
•
full scale Torque calibration:
This setting will be affected by an internal temperature
rise of up to ±0.0015% FS/°C. For more information on full-scale torque setup and
troubleshooting, refer to
Section 6.4 – Calibration Procedure
and
Section 8.1.3 – Full Scale
Torque
.
•
Zero offset:
This setting is affected by an internal temperature rise of up to ±0.002%
Reading/°C. For more information on zero offset setup and troubleshooting, refer to
Section
6.4 – Calibration Procedure
and
Section 8.1.2 – Zero Balance
.
•
coupling losses:
If the coupling becomes hot to the touch, or if the dynamometer or
motor vibrate after a period of running, coupling loss error could occur up to several percent
depending on the size of the motor and dynamometer. For more detail, refer to
Section 4.1.4
– Fixtures and Couplings
.
•
Windage:
Negligible at speeds up to 6000 rpm. This effect is described more extensively
in
Section 4.1.5 – Windage
.
•
mechanical friction:
generally negligible on hD-400 series dynamometers and larger.
on hD-106 and hD-100 the user is cautioned to be aware of the effects that friction may
cause. For more detail, refer to
Section 4.1.6 – Friction
.
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