Precautions For Use - Vexta aStep AS Series Operating Manual

Precautions for use

This section covers limitations and requirements the user should consider when using the
• Operate the motor at a level below the maximum torque.
Operating the motor beyond the maximum torque or placing a continuous constraint on the output shaft may damage
the motor bearings (ball bearings). Be sure to keep the motor load below the maximum torque.
• Do not apply an overhung load in excess of the specified permissible limit.
Be sure to operate the motor within the specified permissible limit of overhung load. Operating it under an excessive
overhung load may damage the motor bearings (ball bearings).
• Operate the motor with a surface temperature not exceeding 100°C (212°F).
The driver has an overheat-protection function, but the motor has no such feature. The motor case's surface
temperature may exceed 100°C (212°F) under certain conditions (ambient temperature, operating speed, duty cycle,
etc.). Keeping the surface temperature of the motor casing below 100°C (212°F) will also maximize the life of the motor
bearings (ball bearings).
• About maximum static torque at excitation
Maximum static torque at excitation represents a value obtained when the motor is excited using a rated current. When
combined with a dedicated driver and while the motor is stopped motor-temperature increases are suppressed due to
a current-reduction of approximately 50% by the current-cutback function. Acceleration and operation at the maximum
static torque at excitation is possible in start-up, but it has approximately 50% holding power after it has stopped. When
selecting a motor for your application, consider the fact that the holding power will be reduced to approximately 50%
after the motor has stopped.
• Use an electromagnetic-brake type for an application involving up/down travel.
When the motor is used in an application involving up/down travel, such as a lifter, use an electromagnetic-brake type
to hold the load in position. To hold the load in position, apply the electromagnetic brake only after the motor has
stopped.
Do not use the brake to bring the moving motor to a halt. Repeated braking for such a purpose will wear the brake hub
excessively, causing its holding ability to drop.
Since the electromagnetic brake is of the non-excitation type, it can also be used to hold the load in position upon the
occurrence of a power failure. However, this is not a secure means of holding the load.
Do not use the electromagnetic brake as a safety brake.
When the driver-protection function is triggered, the motor stops as the current is turned off. The user must set a
controller sequence that will cut off the power to the electromagnetic brake and hold the load in position upon detecting
an "OFF" ALARM output.
• Connecting an electromagnetic-brake type
Be sure to use a junction cable (sold separately) for connection of an electromagnetic-brake type and driver. Direct
connection of the motor cable to the driver will not provide the electromagnetic brake function.
The electromagnetic brake operates via the ON/OFF status of the DC power supply. When connecting the lead wires
of the electromagnetic brake extending from the junction cable, observe the correct polarity. Be sure to connect the
supplied varistor (non-polarized) to protect the switch contacts and prevent noise.
• Install the driver in a vertical orientation.
The driver's heat-dissipation function is designed according to vertical orientation. Installing the driver in any other
orientation may shorten the life of electronic parts due to temperature increases within the driver.
• Preventing leakage current
Stray capacitance exists between the driver's current-carrying line and other current-carrying lines, the earth and the
motor, respectively. A high-frequency current may leak out through such capacitance, having a detrimental effect on the
surrounding equipment. The actual leakage current depends on the driver's switching frequency, the length of wiring
between the driver and motor, and so on.
When providing a leakage current breaker, use the following products, for instance, which have high-frequency signal
protection:
Mitsubishi Electric: NV series
Fuji Electric: EG and SG series
6
AS series.