Dynamic Braking Option, Motor Protection - Omron Q2A Series Technical Manual

3.11

Dynamic Braking Option, Motor Protection

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Install an Electromagnetic Contactor (MC) at the Input Side of the Drive
You can use an MC as an alternative to a molded case circuit breaker (MCCB) when:
• The protective functions of the drive have been triggered
• An emergency stop occurred, and the sequence de-energizes the drive.
If an MC on the input side of the drive (primary side) stops the drive, regenerative braking will not operate, and
the drive will coast to stop.
NOTICE: Do not connect electromagnetic switches or MCs to the output motor circuits without correct sequencing. Incorrect
sequencing of output motor circuits could cause damage to the drive.
NOTICE: Turn the drive ON (Run) and OFF (Stop) a maximum of one time each 30 minutes with the MC on the power source
side to extend the service life of the relay contacts and electrolytic capacitors in the drive. Run and Stop the motor as much as
possible with the drive. The drive can fail if users frequently turn the drive ON and OFF with the MC on the power source side to
Run and Stop the drive. Incorrect operation can decrease the service life of the relay contacts and electrolytic capacitors.
NOTICE: Use an MC to make sure that you can fully remove power to the drive when necessary. Wire the MC to open when a
fault output terminal is triggered.
Note:
• When machinery must not restart after recovery from a momentary power loss that occurred during run, install an MC at the input side
of the drive and set a sequence that does not automatically set the start signal to ON after recovery of power.
• When it is necessary to stop momentary power loss, for example to maintain a circuit that has momentary power loss, use a delayed-
release MC.
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Protect the Braking Resistor/Braking Resistor Unit
Use an MC on the input side (primary side) to prevent damage to the braking resistor/braking resistor unit.
WARNING! Fire Hazard. When you use a braking unit, use a thermal relay on the braking resistors and set a fault contact
output for the braking resistor unit to disconnect drive main power through an input contactor. Incorrect braking circuit
protection can overheat the resistors and cause death or serious injury by fire.
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Install a Thermal Overload Relay on the Drive Output
A thermal overload relay disconnects the power line to the motor during a motor overload condition to prevent
damage to the motor.
Install a thermal overload relay between the drive and motor in these conditions:
• When operating more than one motor from one drive.
• When operating the motor directly from the power line with a power line bypass.
When operating one motor from one drive, it is not necessary to install a thermal overload relay. The drive has
electronic motor overload protection in the drive software.
Note:
• When you install a thermal overload relay, set parameter L1-01 = 0 [Motor Cool Type for OL1 Calc = Disabled].
• Set up a sequence that will trip an external fault (coast to stop) for the contacts of the thermal overload relay.
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General Precautions When Using Thermal Overload Relays
When you use a motor thermal overload relay on the drive output to prevent nuisance trips and overheating of the
motor at low speeds, be sure to think about these application precautions:
• Operation of a low speed motor
Usually, you use thermal overload relays on general-purpose motors (standard motors). When a drive drives a
general-purpose motor, the motor current is approximately 5% to 10% more than with a commercial power
supply. When a motor with a shaft-driven fan operates at low speeds, the cooling capacity decreases. This can
cause the motor to overheat when the load current is in the motor rated value. Enable the electronic thermal
protection in the drive when possible to prevent this problem.
The electronic thermal overload function uses the relation between the speed and heat characteristics in the
variable speed control range to simulate the cooling ability of general-purpose motors and forced-vented motors
to prevent damage to the motor.
• Operating more than one motor from one drive
To disable the overload protection function of the electronic thermal protector of the drive, set L1-01 = 0
[Motor Cool Type for OL1 Calc = Disabled].
SIEPYEUOQ2A01A AC Drive Q2A Technical Manual

3.11 Dynamic Braking Option, Motor Protection

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