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Using the Front Panel Keypad
Inverter Mounting
and Installation
2–30
Step 10: Reading this section will help you make some useful observations when first running
the motor.
Error Codes - If the inverter displays an error code (LED format is “
Exx
”), see “Monitoring
Trip Events, History, & Conditions” on page 6–5 to interpret and clear the error.
Acceleration and Deceleration - The SJ300 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 SJ300 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 A004) 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 configured to
output 60 Hz at full scale. Use the following formula to calculate the RPM.
The theoretical speed for the motor is 1800 RPM (synchronous speed). However, an induction
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 approximately 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 more in depth on
page 3–41
).
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 alter-
nates 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 mainte-
nance personnel.
10
Powerup Test
Observations and
Summary
RPM
Frequency 60×
Pairs of poles
----------------------------------------
Frequency 120×
# of poles
-------------------------------------------
60 120×
4
--------------------- 1800RPM== ==
RUN
STOP
RESET
FUNC.
Run Stop
Monitor Program