MIL-DTL-2212K(SH)
Overload relays shall be constructed to trip within 3 hours when carrying rated relay current. The overload relay
ultimate trip current (see 6.8.102) rating shall be 115 to 125 percent of the motor identification plate current. The
overload relay rating for magnetic controllers shall change not more than 3 percent for each 18 °F change (10 °C
change) in ambient temperature in the range between 68 °F to 158 °F (20 °C and 70 °C). When specified (see 6.2),
direct temperature sensing overload protection systems shall be used to protect variable speed motors (either
variable voltage or variable voltage and frequency control systems) and motors where the duty cycle may be
worsened by operator control or by operational mode which exceeds motor thermal limits because of mechanical or
electrical characteristics of the motor or its load. Overload protection systems using temperature sensing devices in
the motor winding shall be compatible with the temperature sensors. This system shall energize an alarm or
de-energize the motor control. The system shall be fail-safe. Overload relays shall be calibrated for operation at the
122 °F (50 °C) ambient temperature. Overload relays shall meet the endurance requirements of 3.15.
3.16.5.1 Electronic overload protection. Electronic overload relays can be used to protect motors described in
3.16.5. Electronic overload relays shall have tripping characteristics falling within the acceptable band shown on
figure 1. Where overload values might exceed the limits of figure 1, adjustment and settings for the electronic
overload relay shall be in accordance with the manufacturer technical guidance. Electronic overload relay shall
provide means to incorporate a physical switch to allow disabling of the LVR mode of operation. The electronic
overload relay password protection method shall be acceptable to NAVSEA. Unless otherwise specified (see 6.2),
electronic overload relays shall include, but not be limited to the following protection features:
a.
Setup password protection (per Information Assurance (IA) instruction or approval by NAVSEA)
b.
Low voltage protection (LVP) (see 6.8.43)
c.
LVR
d.
Over current
e.
Under current
f.
Low voltage
g.
High voltage
h.
Single phasing
i.
Voltage unbalance
j.
Current unbalance
k.
Phase reversal
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