User Manual

Table Of Contents
AC-induction-Motor-Operation
142 Advanced Digital Motor Controller User Manual V2.1, December 3, 2020
formed by applying balanced rated voltage on the stator windings at the rated frequency.
The small power provided to the motor is due to core losses, friction and winding loses.
The motor will consume the necessary flux I
d
current in order to establish the appropriate
magnetic field. Motor will rotate at almost a synchronous speed, which makes slip nearly
zero (s≈0). Therefore, the motor equivalent circuit is expressed as follows:
FIGURE 9-9. Electrical Representation of ACIM during no load testing
Assuming that the R
s
(Ω), L
s
(H) are much lower than the magnetizing inductance L
m
(H),
the following equation can be extracted:
L
V
2f
I
m
s
s
(9.1)
where V
s
(V) is the phase stator voltage applied (RMS value), f
s
(Hz) is the stator frequency
and I
(A) is the RMS motor amps.
In order to implement the above mentioned no load test with RoboteQ induction motor
controllers, please follow these steps:
Set the operating mode to “Volts per Hertz” mode. Encoder feedback action needed.
Configure the Volt per Hertz setting according to motor nominal voltage (peak value
of stator voltage according to manufacturer) and frequency.
Run the motor without load up to the maximum available voltage (Com-
mand=1000), utilizing small acceleration/deceleration value. Be sure that the con-
figured volt per hertz is correct, by checking the “Stator speed RPM” to be approxi-
mately equal to manufacturer’s synchronous rated speed.
Calculate the applied V
s
by the following equation:
V
mV
1000 23
s
adc

(9.2)
where m
a
is the output PWM level (%1000) applied which is equal to Motor Power output
measurement in Roborun+ utility (-1000 to 1000 range) and V
dc
is the battery volts (V). In
the considered no-load test the m
a
is 1000, therefore the applied voltage can be calculated
as V
V
23
s
dc
Measure the motor RMS current from the utility (Motor Amps). Furthermore, the peak
amps value should be configured as “Rotor Flux current” in the configuration tab.
Calculate the magnetizing inductance for the no load test according to equation
(9.1).