Dynamic Braking Option, Motor Protection; Installing An Electromagnetic Contactor (Mc) At Input Side Of Drive; Installing A Thermal Overload Relay On The Drive Output - YASKAWA GA700 Technical Manual

2.19

Dynamic Braking Option, Motor Protection

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Installing an Electromagnetic Contactor (MC) at Input Side of Drive

When the protective functions of the drive have been triggered, or when an emergency stop has occurred, and
according to the sequence, the main circuit power supply is to be shut off, an MC can be used instead of a molded-
case circuit breaker (MCCB). However, caution should be observed, since if an MC on the input side of the drive
(primary side) is used to forcefully stop the drive, regenerative braking will not operate, and a coast to stop will
occur.
NOTICE: Do not connect electromagnetic switches or MCs to the output motor circuits without proper sequencing. Improper
sequencing of output motor circuits could result in damage to the drive.
NOTICE: To extend the service life of the relay contacts and electrolytic capacitors inside the drive, the MC on the power source
side for turning the drive on (run) and off (stop) should be operated a maximum of one time in 30 minutes. Running and stopping
the motor should be done as much as possible via the run and stop operations of the drive. The drive can be run and stopped by
turning it on and off via the MC on the power source side, but if this is done frequently, it may cause the drive to fail. Improper
operation may shorten the service life of the relay contact and electrolytic capacitor.
NOTICE: Use a magnetic contactor (MC) to ensure that power to the drive can be completely shut off when necessary. The MC
should be wired so that it opens when a fault output terminal is triggered.
Note:
• When it is necessary to prevent machinery from restarting after recovery from a momentary power loss that occurred during run, an
MC can be installed at the input side of the drive, and a sequence that does not automatically set the start signal to ON after recovery of
power should be set up.
• When countermeasures for momentary power loss are required, such as when maintaining a circuit experiencing momentary power
loss, use a delayed release MC.
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Protection of Braking Resistor/Braking Resistor Unit
Use an MC on the input side (primary side) to protect the braking resistor/braking resistor unit.
WARNING! Fire Hazard. When using a braking unit, use a thermal relay on the braking resistors and configure a fault contact
output for the braking resistor unit to disconnect drive main power via an input contactor. Inadequate braking circuit protection
could result in death or serious injury by fire from overheating resistors.
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Installing a Thermal Overload Relay on the Drive Output

A thermal overload relays protect the motor by disconnecting power lines to the motor due to a motor overload
condition.
Install a thermal overload relay between the drive and motor in the following situations:
• When operating multiple motors on a single drive.
• When using a power line bypass to operate the motor directly from the power line.
It is not necessary to install a thermal overload relay when operating a single motor from a single drive. The drive
has electronic motor overload protection built into the drive software.
Note:
• When installing a thermal overload relay, set parameter L1-01 = 0 [Motor Overload Protection Select = Disabled].
• Set up a sequence for tripping 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
Consider the following application precautions when using motor thermal overload relays on the output of drives
to prevent nuisance trips or overheat of the motor at low speeds:
• Low speed motor operation
• When operating multiple motors on a single drive.
• Motor cable length
• Nuisance tripping due to a high drive carrier frequency
Low Speed Operation and Thermal Overload Relays
Generally, thermal overload relays are applied on general-purpose motors (standard motors). When general-
purpose motors are driven by drives, the motor current is approximately 5% to 10% greater than if driven by a
commercial power supply. In addition, the cooling capacity of a motor with a shaft-driven fan decreases when
operating at low speeds. Motor overheating may occur even when the load current is within the motor rated value.
For this reason, the electronic thermal protector inside the drive should be set so it is enabled whenever possible.
YASKAWA ELECTRIC SIEP C710617 01B YASKAWA AC Drive GA700 Technical Manual

2.19 Dynamic Braking Option, Motor Protection

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