User Manual

Table Of Contents
Induction Motor Parameters Calculation
Advanced Digital Motor Controller User Manual 145
Configure the Volt per Hertz setting according to five times lower the motor
nominal voltage (peak value of stator voltage according to manufacturer) and
frequency (1/5 of nominal V/f). The reason for configuring lower V/f ratio than in
no-load test is to appropriately weaken the induced field and reduce the produced
torque at startup, in order to be easier to lock the rotor for the test.
Lock the rotor by appropriate tool/device and increase the command up reaching
the 80% of the rated motor current. If the produced torque is high and the rotor
cannot be locked, then reduce appropriately the Volt per Hertz at configuration and
repeat the test.
Calculate the applied V
s
by utilizing equation (9.2).
Calculate the input phase motor power P
s
by utilizing the following equation:
P=
VI
3
s
dc dc
××h
(9.9)
where V
dc
(V) is the battery dc volts, I
dc
(A) is the battery dc current, η is the controller ef-
ficiency (assume 0.95 efficiency for RoboteQ controllers). Battery volts and amps can be
measured from Roborun+ utility.
Measure the I
q
(A) current from the Roborun+ utility (FOC Torque Amps).
Calculate the L
ls
, L
lr
, R
s
, R
r
motor parameters by applying the equations (9.3) - (9.8).
Example:
For the same induction motor at no load test example, the Volts per Hertz ratio is set 5
times lower than the nominal, that is 0.053. The respective results taken from Roborun+
utility are shown below:
FIGURE 9-12. Locked rotor testing monitoring
Therefore, the input phase motor power P
s
is equal to
P=
VI
3
=
24.22.1 0.95
3
=16.1W
s
dc dc


The power factor is cos
P
VI
16.1
151 24.2
1000 23
18.4
0.59
s
s

, while the equivalent
phase impedance is Z = 0.081 Ω according to equation (9.4).