Part
12470
Rev. 2 3/25/99
11
5.
Test
The motor overload relay should be subjected to a simulated overload and the tripping time
measured. This should be compared to the manufacturer's specifications or the relay's time
curves to make certain that the relay is operating properly. A tolerance of + 15% is usually
acceptable. If the relay's curves or specifications are not available, it is suggested that the
Heat Damage Curve of the motor be used as a guide for maximum trip time at 300% of
motor full load current. TIME DELAY OF MOTOR OVERLOAD RELAYS
TIME DELAY
1.
Set-up CB-832 with:
a.
POWER ON/OFF Switch in OFF position (instrument displays off).
b.
OUTPUT CONTROL knob at minimum
`0'
position.
c.
OUTPUT MODE Switch in center OFF position.
2.
Connect one end of a high-current lead to one side of thermal element or current coil
in overload relay. Connect other end of this lead to the COMMON terminal of test
set.
3.
Connect one end of second high-current lead to other side of thermal element or
current coil in overload relay. Connect other end of this lead to the appropriate
output terminal (see SELECTION OF OUTPUT TERMINAL).
4.
Connect test set to suitable single-phase power supply.
5.
Turn test set on with POWER ON/OFF Switch (instrument displays should light).
6.
Use RANGE Switch to select ammeter range so test current will be near full scale
and no less than 10% of full scale.
7.
Put ammeter DISPLAY MODE Switch in MEMORY position.
8.
Connect a pair of light leads (timer leads) from Normally Closed Contacts or
Normally Open Contacts of overload relay to binding posts of test set labeled
CONTACTS.
9.
Select appropriate timer STOP MODE.
10.
Select desired timer display mode and range.
11.
Rotate OUTPUT CONTROL knob clockwise and momentarily press OUTPUT
MODE Switch in MOMENTARY and release. Observe current reading retained by
ammeter.
12.
Continue to rotate OUTPUT CONTROL knob clockwise while jogging (repeatedly
moving to MOMENTARY position and releasing) OUTPUT MODE Switch until
desired test current is reached. Suggested test current is three times (3x) the rating of
thermal relays or three times (3x) the pick-up current of magnetic relays.
If the relay utilizes a high impedance thermal element or operating coil and the
