Control apparatus for two-speed compressor
AssigneeLennox Industries Inc.
InventorsDavid M. Pfarrer, Sidney A. Parker
Life of this patent
Estimating the term…
Abstract
The disclosure describes a refrigerant compressor of the type driven by a motor capable of operating at a low speed and a high speed, the motor including first, second and third stator coils. First, second and third temperature sensors are located adjacent the first, second and third stator coils, respectively, for detecting any change in temperature of the coils. If the temperature of any of the stator coils exceeds a perdetermined value, a control device operates a switch in a pilot circuit that turns off the motor before damage from excessive heat can occur. A unique contactor assembly utilizing both electrical and mechanical interlocks interconnects the stator coils to provide two speed operation.
Claims4
In a refrigerant compressor of the type having a compression mechanism for receiving refrigerant gas from a suction line, compressing the refrigerant gas and discharging the compressed refrigerant gas through a discharge line, and a motor for rotating drive shaft means in the compression mechanism at low speed and at high speed, said motor including a single stator coil assembly comprising first, second and third stator coils, each stator coil having an inner end point connected to a common conductor and also having an outer end point, improved apparatus for controlling the operation of the motor from a source of electrical power comprising:
- a fourth stator coil having a first end point connected to the outer end point of the first stator coil;
- a fifth stator coil having a first end point connected to the outer end of the second stator coil;
- a sixth stator coil having a first end point connected to the outer end point of the third stator coil;
- a tying relay coil for operating tying relay contacts that switch the stator coils between a high speed interconnection and a low speed interconnection;
- a low speed relay coil for operating low speed relay contacts that apply power from the source to the stator coils after the stator coils have been switched to the low speed interconnection to achieve low speed operation so that damaging surge voltages and currents in the stator coils are prevented;
- a high speed relay coil for operating high speed contacts that apply power from the source to the stator coils after the stator coils have been switched to the high speed interconnection to achieve high speed operation so that damaging surge voltages and currents in the stator coils are prevented;
- a control circuit including a first branch for controlling the high speed relay coil and a second branch for controlling the low speed relay coil;
- electrical interlock means in the control circuit for preventing the simultaneous operation of the low speed relay coil and the high speed relay coil;
- mechanical interlock means to prevent the simultaneous operation of the low speed relay contacts and the high speed relay contacts;
- first sensor means located adjacent the first stator coil for indicating a change in temperature of the first stator coil;
- second sensor means located adjacent the second stator coil for indicating a change in temperature of the second stator coil;
- third sensor means located adjacent the third stator coil for indicating a change in temperature of the third stator coil;
- and
- control means for interrupting the flow of current in the first and second branches in response to an indication from any of said sensors that the temperature of any of said stator coils exceeds a predetermined value, so that the control circuit is prevented from operating the tying relay coil, low speed relay coil, or high speed relay coil.
Dependencies are inferred from the claim text.