Generator power management
AssigneeCarrier Corporation
InventorsJohn Robert Reason, Joao Eduardo Navarro de Andrade
Life of this patent
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Abstract
A system and method for monitoring and controlling an electrically driven transport refrigeration unit under varying operating conditions while maintain the system generator within its electric current and temperature limitations is disclosed. Specifically, the present invention the management of generator power through the combined use of controls for a suction modulation valve (an “SMV”), for diesel engine speed control, and for electronic expansion valve (“EXV”) superheat settings.
Claims6
A process for controlling generator power in an electrical transport refrigeration unit and for maximizing capacity for said refrigeration unit, said refrigeration unit being controlled by a microprocessor controller, said process comprising the steps of:
- i. monitoring generator current for said refrigeration unit;
- ii. comparing said generator current to a predetermined value stored in the microprocessor controlling said refrigeration unit;
- and
- iii. sending a signal from said microprocessor to a suction modulation valve, thereby altering the mass flow within the refrigeration unit;
- whereby the current draw resulting from the altered mass flow corresponds approximately to the predetermined value stored in the microprocessor.
A process for limiting the temperature of a generator in an electrical transport refrigeration unit, said refrigeration unit being controlled by a microprocessor controller, said process comprising the steps of:
- i. monitoring the generator temperature for said refrigeration unit;
- ii. comparing said generator temperature to a predetermined value stored in the microprocessor controlling said refrigeration unit;
- and
- iii. selectively sending a signal from said microprocessor to restrict a suction modulation valve, thereby reducing the mass flow within the refrigeration unit when said generator temperature exceeds the predetermined value;
- whereby the reduced mass flow lowers the generator temperature below the predetermined value stored in the microprocessor
A process for accommodating a change in speed from high to low engine speed conditions for a multispeed engine on an electrical transport refrigeration unit, said refrigeration unit being controlled by a microprocessor, said process comprising the steps of:
- i. receiving one or more operating parameters;
- ii. analyzing said operating parameters to determine whether low engine speed conditions are present;
- iii. selectively actuating a suction modulation valve in response to the presence of said low engine speed conditions, thereby reducing the current draw below a predetermined current draw limit corresponding to low engine speed conditions, said predetermined current draw limit being stored in said microprocessor;
- and
- iv. delaying the actual speed reduction of said engine until the current draw of said transport refrigeration unit does not exceed said predetermined current draw limit.
A process for accommodating an increase in the refrigerant pumping capacity of a compressor in an electrical transport refrigeration unit, said refrigeration unit being controlled by a microprocessor, said process comprising the steps of :
- i. increasing the restriction of an electronic expansion valve, thereby reducing the mass flow rate and the current draw of the transport refrigeration unit;
- ii. subsequently de-energizing an unloader, thereby increasing the mass flow and current draw of said transport refrigeration unit;
- iii. gradually removing the increased restriction of said electronic expansion valve after said unloader has been de-energized, thereby maintaining the current draw of said transport refrigeration unit below a preselected limit.
A process for accommodating an increase in the refrigerant pumping capacity of a compressor in an electrical transport refrigeration unit through manipulation of superheat levels so as to avoid undue increases in current draw and instability in superheat control, said refrigeration unit being controlled by a microprocessor, said process comprising the steps of:
- i. increasing the desired superheat level by a fixed, predetermined offset, thereby increasing the restriction of the electronic expansion valve so as to reduce the mass flow rate and the current draw of the transport refrigeration unit;
- ii subsequently de-energizing an unloader, thereby increasing the mass flow and current draw of said transport refrigeration unit;
- and
- iii gradually reducing the desired superheat level by said fixed, predetermined offset,
- whereby the manipulation of the superheat level prevents the net increase in the current draw of the refrigeration unit.
A process for accommodating an increase in the refrigerant pumping capacity of a compressor in a transport refrigeration unit through manipulation of superheat levels so as to avoid undue increases in current draw, said refrigeration unit being controlled by a microprocessor, said process comprising the steps of:
- i. increasing the desired superheat level by a fixed, predetermined offset, thereby increasing the restriction of the electronic expansion valve so as to reduce the mass flow rate and the current draw of the transport refrigeration unit;
- ii subsequently de-energizing an unloader, thereby increasing the mass flow and current draw of said transport refrigeration unit;
- and
- iii gradually reducing the desired superheat level by said fixed, predetermined offset,
- whereby the manipulation of the superheat level prevents the net increase in the current draw of the refrigeration unit.
Dependencies are inferred from the claim text.