How to choose the right thermal relay?
Author: Shenzhen Yuan Zhi Electronics Co., Ltd.Time:2018-03-01 16:26:58Views:1020【SML】
How to properly select and use a thermal relay is an old topic.
However, many units have still occasioned the accidental burning of the
motor due to unreasonable selection or use of the thermal rela...
label:
How to properly select and use a thermal relay is an old topic.
However, many units have still occasioned the accidental burning of the
motor due to unreasonable selection or use of the thermal relay.
Thermal
relay bimetal, fusible alloy, thermistor, thermal magnetic and many
other kinds, are based on the use of current thermal effect of a
protective relay made, widely used in motor overload protection Therefore, the selection and use of thermal relays in addition to
comply with the general provisions, but also pay attention to the
following points:
1.
Star / delta start control circuit, the thermal relay installation
location is different, the selection of the thermal relay specifications
are not the same: the main circuit thermal relay string in the total
line when the current setting value should be protected motor rated
current The same value, the main circuit in the thermal relay string delta
running circuit in the setting value should be protected motor rated
current value of 1 / 1.732.
2. Thermal relays generally have manual reset and automatic reset two reset forms.
This
relay, thermal relay use two kinds of reset the form of conversion, by
adjusting the reset screw to complete the thermal relay factory, the
manufacturer generally set to automatically reset state. In
use, the thermal relay should be set to manual reset or automatic reset
state according to the specific circumstances of the control loop. Under normal circumstances, should follow the thermal relay protection
action even if the thermal relay automatically reset, be protected
relay, thermal relay motor selection should not be automatically
restarted principle, otherwise the thermal relay should be set to manual
reset state.
This is to prevent the motor from restarting the damaged equipment several times after the fault has not been cleared. (For example, pushbutton controlled manual start and manual stop
control circuits are usually used. The thermal relay can be set to auto
reset mode. The automatic start circuit with automatic component control
should set the thermal relay to manual reset mode.
3.
For thermal relays with different rated current levels but the same
thermal element adjustment range (for example, thermal relays of the
JR16 series have a thermal element setting of 14A-16A for both thermal
relays rated at 20A and 60A Adjustment range) of the selection, should check the thermal relay
used in the ambient temperature and the motor is protected ambient
temperature.
When
the thermal relay ambient temperature is higher than the protected
motor ambient temperature above 15 ℃, you should use relays, thermal
relays use larger rated current level thermal relay; when the thermal
relay ambient temperature is lower than the motor to be protected When the ambient temperature is below 15 ℃, use a smaller one rated current thermal relay.
4.
For repeated short-time work motor overload protection, the test should
be repeated in the field, relays, thermal relays used to adjust the
selection can be more reliable protection. The
first method is to set the thermal relay setting current slightly lower
than the rated current of the motor. If it is found to be constantly
operating during operation, gradually adjust the setting value of the
thermal relay until it meets the operation requirements.
2018-03-01
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