Nonvolatile Thermal Memory Method And Apparatus For Electronic Overload Relay
First Claim
1. A method of protecting a motor with an electronic overload relay, the overload relay including a power supply having a capacitor and a microcontroller having a volatile memory, the method comprising:
- during an initial powered state of the motor, using the microcontroller for(a) monitoring a supply voltage to the capacitor, and(b) storing in the volatile memory an initial value of a motor thermal model;
in response to the motor entering an unpowered state, discontinuing the monitoring of the supply voltage to the capacitor; and
upon entering a subsequent powered state of the motor, using the microcontroller for(c) determining a change in capacitor voltage,(d) retrieving the stored value from the volatile memory and(e) based in part on the change in capacitor voltage, adjusting the stored value to a modified value of the thermal model.
1 Assignment
0 Petitions
Accused Products
Abstract
An electronic overload relay includes a microcontroller having an internal random-access memory (RAM) in which a motor thermal model is stored. The microcontroller is coupled to a power supply having a bulk storage capacitor. In response to a trip or stop condition of a protected motor, the thermal model is maintained in the RAM with no timing or decrementing. When the motor restarts, the microcontroller calculates a change in capacitor voltage to estimate the motor stop duration. The thermal model is decremented based on the estimated duration.
7 Citations
20 Claims
-
1. A method of protecting a motor with an electronic overload relay, the overload relay including a power supply having a capacitor and a microcontroller having a volatile memory, the method comprising:
-
during an initial powered state of the motor, using the microcontroller for (a) monitoring a supply voltage to the capacitor, and (b) storing in the volatile memory an initial value of a motor thermal model; in response to the motor entering an unpowered state, discontinuing the monitoring of the supply voltage to the capacitor; and upon entering a subsequent powered state of the motor, using the microcontroller for (c) determining a change in capacitor voltage, (d) retrieving the stored value from the volatile memory and (e) based in part on the change in capacitor voltage, adjusting the stored value to a modified value of the thermal model. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. An electronic overload relay for monitoring a motor thermal model, the overload relay comprising:
-
a current transformer having an overvoltage protection circuit and a power supply with a capacitor; a processor; and a volatile memory device storing instructions that, when executed by the processor, cause the electronic overload relay to monitor a supply voltage to the capacitor during a powered state, store an initial value of a motor thermal model, discontinue, in response to entering an unpowered state, to monitor the supply voltage to the capacitor, and upon resuming the powered state, adjust the initial value to a modified value based in part on a change in capacitor voltage. - View Dependent Claims (11, 12, 13, 14, 15)
-
-
16. A computer program product, comprising one or more non-transitory tangible media having a computer readable program logic embodied therein, the computer readable program logic configured to be executed to implement a method for protecting a motor with an electronic overload relay, the overload relay including a power supply with a capacitor and a microcontroller having a volatile memory, the method comprising:
-
monitoring a supply voltage to the capacitor during a first powered state of the motor; storing an initial thermal value of a motor thermal model and an initial capacitor voltage; in response to the motor entering an unpowered state, discontinuing the monitoring of the supply voltage to the capacitor; and in response to the motor entering a second powered state, subsequent to the unpowered state, determining (a) a change in capacitor voltage between the first powered state and the second powered state and (b) a discharge rate of the capacitor, calculating duration of the unpowered state based on the change in capacitor voltage and on the discharge rate of the capacitor, and adjusting the initial thermal value to a modified thermal value based on the duration. - View Dependent Claims (17, 18, 19, 20)
-
Specification