Hitachi 152SO, Installation & Operation Manual

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PN-152SO Switch Overload Relay
Copyright 2019 SM 5929 Rev. 23, March 2019 1-1
1. INTRODUCTION
1.1. Introduction
In the PN-150 line of relays the PN-150SO is the equivalent of the ORP-66 D.C. switch
overload relay. It is furnished primarily for the overload protection of high voltage D. C.
switch machines. This relay can be used also to protect low voltage D. C. switch
machines under the same current conditions. This relay, with a different thermal
resistor, can be furnished to match a motor with another D. C. current range.
The operating relay coil, paralleled by a thermal resistor, is in series with the motor.
When the motor current becomes excessive, the operating relay picks up. This picks up
the stick relay, which then releases the operating relay and deenergizes the switch
control relay, thereby opening the motor control circuit.
The thermal resistor has a high temperature coefficient of resistance, so that with
excessive motor current, its resistance will increase giving a longer cut-out time for a
lower current and a shorter cut-out time for a higher excessive motor current.
1.2. Shock Indicators
WARNING
Any relay showing shock indicator activation should be sent
to the shop for inspection before placing the relay into
service. Failure to assure proper function of this relay could
result in severe personal injury or death.
The shock indicator (P/N J680167-0012) shows red when the relay has been subjected
to shock in excess of a safe level (i.e., dropped) during shipment or transport. This is an
indication that the relay may have mechanical damage and may not meet electrical
specifications.
The relay should be opened and visually inspected for damage (i.e., kinked springs).
Mechanical settings should be checked, recalibrated, and tested according to
specifications by a qualified individual.