Powerup Test Observations And Summary - Omron MX2 User Manual

Using the Front Panel Keypad
2-5-7

Powerup Test Observations and Summary

Step 7 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 "E xx"), see
"Monitoring Trip Events, History, & Conditions" on page 238 to interpret and
clear the error.
Acceleration and Deceleration – The MX2 inverter has programmable
acceleration and deceleration value. The test procedure left these at the
default value, 10 seconds. You can observe this by setting the frequency F001
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-per-
formance MX2 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 read-
out. The maximum frequency setting (parameter A044) 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 calcu-
late the rpm.
Frequency × 60
=
Speed in RPM
Pairs of poles
The theoretical speed for the motor is 1800 RPM (speed of torque vector rota-
tion). 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 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.
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 dia-
gram to the right depicts the modes
and the mode transitions via keypad.
Note Some factory automation devices such as PLCs have alternative Run/Pro-
gram modes; the device is in either one mode or the other. In the Omron
inverter, however, Run Mode alternates with Stop Mode, and Program Mode
alternates with Monitor Mode. This arrangement lets you program some value
while the inverter is operating – providing flexibility for maintenance person-
nel.
Frequency × 120 60×120
= =
#of poles 4
Run
Monitor
Section 2-5
=
1800 RPM
Stop
Program
57