YOKOGAWA WT1800 User Manual page 114

Appendix 1 Symbols and Determination of Measurement Functions
Note
• u1, u2, and u3 represent the sampled voltage data of elements 1, 2, and 3, respectively. i1, i2, and i3
represent the sampled current data of elements 1, 2, and 3, respectively.
• The numbers (1, 2, and 3) that are attached to delta computation measurement function symbols have no
relation to the element numbers.
• For details on the rms, mean, dc, rmean, and ac equations of delta computation mode, see page App-1.
• We recommend that you set the measurement range and scaling (conversion ratios and coefficients) of
the elements that are undergoing delta computation as closely as possible. Using different measurement
ranges or scaling causes the measurement resolutions of the sampled data to be different. This results in
errors.
Measurement Functions Used in the Motor Evaluation Function
(Option)
Measurement
Function
Rotating speed
Torque
Synchronous speed
Slip
Monitor output
App-8
When the input signal from the revolution sensor is DC voltage (an analog signal):
S(AX + B) – NULL
S:
A:
X:
B:
NULL: null value
When the input signal from the revolution sensor is the number of pulses:
X
S
– NULL
N
S:
X:
N:
NULL: null value
When the input signal from the torque meter is DC voltage (an analog signal):
S(AX + B) – NULL
S:
A:
X:
B:
NULL: null value
When the input signal from the torque meter is a pulse signal:
S(AX + B) – NULL
S:
A:
X:
B:
NULL: null value
The WT1800 computes the torque pulse coefficient and torque pulse offset
from torque values (the unit is N•m) at the upper and lower frequency limits.
Normally use a scaling factor of 1. If you are using a unit other than N•m, set the
unit conversion ratio.
120 • the frequency of the frequency measurement source (Hz)
• The unit of synchronous speed is fixed to min – 1 or rpm.
• Normally use the voltage or current supplied by the motor as the frequency
SyncSp
measurement source. If you use any other signals, the synchronous speed
may not be computed correctly.
SyncSp – Speed
Slip
[%]
SyncSp
2π Speed
•
When the unit of speed is min – 1 or rpm, the unit of torque is N•m, and the
Pm
scaling factor is 1, the unit of motor output Pm is W.
Methods of Computation and Determination
scaling factor
slope of the input signal
input voltage from the revolution sensor
offset
scaling factor
number of input pulses from the revolution sensor per minute
number of pulses per revolution
scaling factor
slope of the input signal
input voltage from the torque meter
offset
scaling factor
torque pulse coefficient
pulse frequency
torque pulse offset
Number of motor poles
100
•
Torque
•
Scaling factor
•
60
IM WT1801-03EN