Hitachi 152SO, Installation & Operation Manual, Page: 19 / 36

PN-152SO Switch Overload Relay
Copyright 2019 SM 5929 Rev. 23, March 2019 4-5
4.1.6. Service Recommendations
Relays should be checked periodically in service to assure they give the desired delay
times. This may be done by obstructing the switch points, measuring the current at
which the clutch slips and noting the time it takes for the relay to function.
For accurate measurement of time for the relay to operate, about five minutes should be
allowed for the thermal resistor to cool. In no case should another operation be tried
with less than six seconds cooling time or the relay may not have sufficient motor surge
current protection.
When adjusting or working on a switch machine, apply a jumper between terminals HV+
and HV- to shunt out the thermal resistor. Of course, the jumper must be removed for
normal circuit functioning.
Switch machine clutch slippage should be maintained at approximately 13 amperes. It
the clutch slippage current is excessively low, the overload relay will not function and
might be damaged.
Table 4-2. Final Calibration Values
Relay P/N
Thermal Resistor Operating Time
P/N Nom. Ohms @Amps Sec. @Amps Sec.
N322522-802 N436521 .046 13 5 15 3
N322522-001 N398311 .030 13 10 15 6