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26
Inverter Mounting and Installation
Powerup Test Observations and Summary
Reading this section will help you make some useful observations when first running the
motor.
Error Codes – If the inverter displays an error code (format is
the SJ100 instruction manual for instructions on how to interpret and clear the error.
Acceleration and Deceleration - The SJ100DN inverter has programmable acceleration
and deceleration values. The test procedure left these at the default value, 10 seconds.
You can observe this by setting the potentiometer at about half speed before running the
motor. Then press RUN, and the motor will take 5 seconds to reach a steady speed. Press
the STOP key to see a 5 second deceleration to a stop.
State of Inverter at Stop – If you adjust the motor's speed to zero, the motor will slow
to a near stop, and the inverter turns the outputs OFF. The high-performance SJ100DN
can rotate at a very slow speed with high torque output, but not zero (must use servo
systems with position feedback for that feature). This characteristic means you must use
a mechanical brake for some applications.
Interpreting the Display - First, refer to the output frequency display readout. The
maximum frequency setting (parameter A_04) defaults to 50 Hz or 60 Hz (Europe and
United States, respectively) for your application.
Example: Suppose a 4-pole motor is rated for 60 Hz operation, so the inverter is config-
ured to output 60 Hz at full scale. Use the following formula to calculate the RPM.
Speed in RPM
The theoretical speed for the motor is 1800 RPM (speed of torque vector rotation).
However, the motor cannot generate torque unless its shaft turns at a slightly different
speed. This difference is called slip. So it's common to see a rated speed of approxi-
mately 1750 RPM on a 60 Hz, 4-pole motor. Using a tachometer to measure shaft speed,
you can see the difference between the inverter output frequency and the actual motor
speed. The slip increases slightly as the motor's load increases. This is why the inverter
output value is called "frequency," since it is not exactly equal to motor speed. You can
program the inverter to display output frequency in units more directly related to the load
speed by entering a constant (discussed in Chapter 3 in the SJ100 instruction manual).
Run/Stop Versus Monitor/Program Modes –
The Run LED on the inverter is ON in Run Mode,
and OFF in Stop Mode. The Program LED is ON
when the inverter is in Program Mode, and OFF for
Monitor Mode. All four mode combinations are
possible. The diagram to the right depicts the
modes and the mode transitions via keypad.
NOTE: Some factory automation devices such as PLCs have alternate Run/Program
modes; the device is in either one mode or the other. In the Hitachi inverter, however,
Run Mode alternates with Stop Mode, and Program Mode alternates with Monitor
Mode. This arrangement lets you program some values while the inverter is operating—
providing flexibility for maintenance personnel.
×
Frequency
60
Frequency 120
=
----------------------------------------
=
-------------------------------------------
Pairs of poles
"E x
x"), see Chapter 6 in
×
×
60 120
=
-------------------- -
# of poles
4
STOP
RESET
Run
FUNC.
Monitor
1800RPM
=
Stop
RUN
Program
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