Refrigerator Apparatus Including Motor Cooling Means

Abstract

The open drive motor for a refrigeration apparatus is mounted in a hermetic casing containing a quantity of a mixture consisting of a refrigerant and a lubricating oil. A passage extends from the upper portion of the casing to an auxiliary condenser, and a second passage returns condensed mixture to the motor casing. The auxiliary condenser is cooled by a metered flow of refrigerant from the condenser of the apparatus. The flow is metered to supply the condensed mixture in sufficient quantity to effectively cool the motor during continuous operation of the motor at full load.

Description

BACKGROUND OF THE INVENTION

In certain refrigeration systems the compressor is operated by an open drive motor. The open drive motor is mounted externally of, and separate from, the compressor, as distinguished from an enclosed drive wherein the motor is mounted in the compressor housing. The advantages of an open drive motor are well known, especially in that the motor can be quickly and conveniently serviced and replaced if necessary. Also, if desired, the motor can be replaced by a turbine or other primer mover. The advantage of a refrigerant cooled motor is also well known. The main advantage being in that the rating of the motor may be reduced 25 percent or more. This effects a saving of several thousand dollars in motor costs for a motor drive on large tonnage refrigeration apparatus.

Various arrangements have been proposed to cool open drive motors by refrigeration. In one arrangement, there is provided an auxiliary compressor and condenser. The refrigerant vapor is passed from the motor casing to the inlet of the compressor and the liquid refrigerant is conveyed from the auxiliary condenser to the motor casing. In that arrangement, a separate lubricating system is necessary to provide oil to the motor bearings. The motor bearings are sealed off to prevent the leakage of oil from the bearings into the refrigerant in the motor casing. It is necessary to periodically inspect the seals to make certain that the oil is not leaking into the refrigerant, especially where the compressor is of the reciprocating piston type. Also, a separate compressor has to be operated and maintained. In another arrangement, the refrigerant is passed directly from the main refrigerating apparatus to the motor casing. That arrangement has the same disadvantage in regard to supplying the lubricant to the motor bearings.

SUMMARY OF THE INVENTION

In this invention, the hermetically sealed motor casing is provided with the supply of mixture containing refrigerant and lubricating oil. A passage extends from the upper portion of the motor casing to the auxiliary condenser, and a passage from the condenser to the motor casing for the return of liquid refrigerant. Means is provided for maintaining the refrigerant oil mixture in the motor casing at a selected level. There is a flow metering means in a line extending from the main condenser to the cooling coil in the auxiliary condenser and is arranged to meter the refrigerant through the coil so as to maintain a flow of liquid refrigerant and oil mixtures from the auxiliary condenser to the motor casing sufficient to properly cool the motor when operated consistently under full load.

BRIEF DESCRIPTION OF THE DRAWING

The drawing discloses a schematic view of a refrigeration system, the compressor of which is driven by a motor embodying my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The refrigeration system disclosed in the drawing includes a centrifugal type compressor 10 operable to draw refrigerant vapor from the cooler 11 through a passageway 12. The compressed vapor is discharged from the compressor through a line 13 to a condenser 14.

The condenser is provided with a refrigerant sump 20 containing a flow control metering valve 21 for the discharge of liquid refrigerant through line 23 to the lower portion of the cooler 11.

The motor for driving the compressor 10 includes a stator 25 and a rotor 27. The rotor 27 is journaled for rotation in bearigs 30, 31 mounted in the end walls 33, 35 of the hermetically sealed casing 37.

A first passageway 40 extends from the upper portion of the casing 37 to an auxiliary condenser 41. A heat exchanging coil 43 is mounted in the condenser 41 and is supplied with liquid refrigerant from the main condenser 14 through a line 44 which includes a flow control device 45. Refrigerant is returned from the heat exchanger 43 to the cooler. As shown in the drawing, the return line from the heat exchanger 43 is connected in line 23.

Liquid refrigerant is conveyed from the auxiliary condenser 41 to the motor casing 37 by line 47. A supply of a mixture containing a refrigerant and a lubricating oil is maintained in the lower portion of the motor casing 37. The refrigerant vapor passing through the passage 40 to the auxiliary condenser contains a quantity of the lubricating oil entrained therein. The refrigerant vapor is condensed in the condenser 41 and returned through the passage 47, together with the oil entrained in the vapor. The mixture is maintained at a predetermined level indicated at 50 by a metering valve 51 operated by a float 52. The valve 51 is mounted in a chamber 53.

A pump 55 driven by a motor 56 operates to pump the mixture from the motor casing 37 through a line 57 for discharge onto the bearing 30 and against the confronting end of the rotor 27. The mixture is also pumped through line 60 to the bearing 31 and to the shaft seal 62.

Inasmuch as the auxiliary condenser 41 is cooled with refrigerant from the main condenser 14, the mixture flowing through the return passage 47 to the motor casing is at an exceptionally low temperature. The motor is cooled to a temperature substantially equal to the temperature in the cooler 11. This results in maintaining the oil in the mixture at high viscosity to provide good lubrication. This arrangement has the advantage of permitting the use of a refrigerant in the mixture different from the refrigerant in the refrigeration apparatus.

The meter device 45 may be in the form of a fixed orifice or an adjustable valve. In any event, the flow through the return passage 47 is such as to provide proper cooling of the motor when operated consistently at full load. Employing refrigerants conventionally used and conventional types of lubricating oils, the mixture may consist of 40 -- 50 percent oil and 50 -- 60 percent refrigerant.

While I have described the preferred embodiments of my invention, it is to be understood that the invention is not limited thereto, but may be otherwise embodied within the scope of the following claims.

Claims

I claim:

1. A refrigeration system including a compressor, a condenser and a cooler, a motor operatively connected to the compressor for operating the same, said motor being mounted in a hermetically sealed casing, a quantity of mixture of a refrigerant and a lubricating oil in the motor casing, a passage extending from the upper portion of the motor casing to an auxiliary condenser and a second passage extending from the auxiliary condenser to the motor casing, means for maintaining said mixture at a selected level in the motor casing, a heat exchanging coil mounted in said auxiliary condenser, a refrigerant line extending from the apparatus condenser to said heat exchanger and a return line extending from the heat exchanger to the cooler of the apparatus, a flow metering device in said line from said apparatus condenser to said heat exchanger and operable to meter a flow of refrigerant from the apparatus condenser to said heat exchanger, said flow being sufficient to effectively cool the motor operating under maximum load, a pump operable to circulate the mixture in said motor casing and discharging the same to the bearings of said motor and against said motor components.

2. Apparatus as set forth in claim 1 wherein the mixture in said motor casing consists of 50 percent refrigerant and 50 percent lubricating oil.