Control circuits for compressor motors including multiple capacitors
A compressor assembly includes a compressor motor having a main winding coupled with a line terminal to receive power from a line voltage source, and an auxiliary winding. The assembly includes first and second capacitors each coupled between the line terminal and the auxiliary winding, a first relay to selectively couple the first capacitor and the second capacitor in parallel, a second relay coupled to selectively inhibit the supply of power from the line voltage source to the auxiliary winding via the first capacitor, and a control circuit configured to close the first relay in response detection of excess load condition criteria, and to subsequently open the first relay in response to detection of normal load condition criteria. The excess load condition criteria and the normal load condition criteria each include at least one of a voltage of the main winding and a voltage of the auxiliary winding.
1. A compressor assembly comprising:
a compressor motor coupled to operate a compressor of a heating, ventilation and/or air-conditioning (HVAC) system, the compressor motor including a stator core having a stator yoke and a plurality of teeth extending from the stator yoke toward a central opening, the central opening extending from a first end of the stator core to a second end of the stator core opposite the first end, the plurality of teeth spaced apart from one another and defining a plurality of slots between the plurality of teeth, the compressor motor further including a main winding and an auxiliary winding located within the plurality of slots and wrapped around the plurality of teeth, the main winding coupled with a line terminal to receive power from a line voltage source;
a first capacitor coupled between the line terminal and the auxiliary winding to supply power to the auxiliary winding from the line voltage source;
a second capacitor coupled between the line terminal and the auxiliary winding to supply power to the auxiliary winding from the line voltage source;
a first relay coupled between the first capacitor and the second capacitor to selectively couple the first capacitor and the second capacitor in parallel;
a second relay coupled between the first capacitor and the auxiliary winding to selectively inhibit the supply of power from the line voltage source to the auxiliary winding via the first capacitor; and
a control circuit coupled to control switching operation of the first relay and the second relay, the control circuit configured to close the first relay in response to detection of excess load condition criteria, and to subsequently open the first relay in response to detection of normal load condition criteria, the excess load condition criteria and the normal load condition criteria each including at least one of a voltage of the main winding and a voltage of the auxiliary winding.
2. The compressor assembly of claim 1 , wherein the control circuit is configured to close the first relay during an initial startup time period of the compressor motor, and subsequently open the first relay in response to a detection of startup condition criteria, the startup condition criteria including at least one of an expiration of the initial startup time period, the voltage of the main winding and the voltage of the auxiliary winding.
3. The compressor assembly of claim 1 , wherein the control circuit is configured to, in response to the detection of the excess load condition criteria:
open the second relay to disconnect the first capacitor from the line terminal or the auxiliary winding prior to the closing the first relay;
subsequent to opening the second relay, wait a specified voltage balance time period before the closing of the first relay; and
after the closing of the first relay, close the second relay to connect the first capacitor and the second capacitor to the line terminal or the auxiliary winding, to supply power from the line terminal to the auxiliary winding via the first capacitor and the second capacitor.
4. The compressor assembly of claim 3 , further comprising a resistor coupled between the second relay and the second capacitor, wherein the second relay is coupled to connect the first capacitor with the second capacitor via the resistor when the second relay disconnects the first capacitor from the line terminal or the auxiliary winding.
5. The compressor assembly of claim 4 , further comprising a diode including a cathode and an anode, wherein the cathode is coupled with the resistor and the anode is coupled with the auxiliary winding.
6. The compressor assembly of claim 1 , further comprising a diode including a cathode and an anode, wherein the cathode is coupled with the first capacitor and the anode is coupled with the auxiliary winding.
7. The compressor assembly of claim 1 , wherein the control circuit is configured to receive a first current value indicative of a current through the main winding, receive a second current value indicative of a current through the auxiliary winding, and open the second relay in response to at least one of the first current value and the second current value exceeding a current overload threshold.
8. The compressor assembly of claim 1 , wherein a capacitance value of the first capacitor is equal to a capacitance value of the second capacitor.
9. The compressor assembly of claim 1 , wherein the compressor motor comprises a permanent split capacitor (PSC) motor.
10. The compressor assembly of claim 1 , further comprising:
a third capacitor coupled between the line terminal and the auxiliary winding to supply power to the auxiliary winding from the line voltage source; and
a third relay coupled between the first capacitor, the second capacitor and the third capacitor, to selectively couple the third capacitor in parallel with the first capacitor and the second capacitor, wherein the control circuit is coupled to control switching operation of the third relay.
11. The compressor assembly of claim 1 , wherein:
the first capacitor comprises a first capacitor film disposed in an integral multi-capacitor housing; and
the second capacitor comprises a second capacitor film disposed in the integral multi-capacitor housing.
12. The compressor assembly of claim 11 , wherein the integral multi-capacitor housing includes a third capacitor film adapted to couple between the line voltage source and a fan motor for a condenser unit of the heating, ventilation and/or air-conditioning (HVAC) system.
13. The compressor assembly of claim 1 , wherein the control circuit is configured to determine at least one of a rotational speed of the motor and a load of the motor according to a polynomial equation having specified coefficients, and wherein the voltage of the main winding and the voltage of the auxiliary winding comprise inputs to the polynomial equation.
14. The compressor assembly of claim 13 , wherein:
the control circuit is configured to calculate a phase difference between the voltage of the main winding and the voltage of the auxiliary winding;
the phase difference comprises one or more inputs to the polynomial equation;
the polynomial equation has a form of rotational speed or load=p 0 +p 1 x+p 2 y+p 3 z+p 4 x 2 +p 5 xy+p 6 xz+p 7 y 2 +p 8 yz+p 9 z 2 +p 10 x 3 +p 11 x 2 y+p 12 x 2 z+p 13 xy 2 +p 14 y 3 +p 15 y 2 z+p 16 xz 2 +p 17 yz 2 +p 18 z 3 +p 19 xyz;
x is the voltage of the main winding;
y is the voltage of the auxiliary winding;
z is the phase difference; and
p 0 -p 19 are the specified coefficients.
15. The compressor assembly of claim 1 , further comprising a thyristor electrically coupled with the second relay.
16. A compressor apparatus comprising:
a compression unit; and
the compressor assembly of claim 1 coupled to drive the compression unit.
17. The compressor apparatus of claim 16 , wherein the compression unit comprises a scroll compressor.
18. The compressor assembly of claim 1 , wherein the control circuit is configured to calculate a phase difference between the voltage of the main winding and the voltage of the auxiliary winding by:
tracking a waveform of the voltage of the main winding to generate a main winding phase angle;
tracking another waveform of the voltage of the auxiliary winding to generate an auxiliary winding phase angle; and
determining the phase difference according to the main winding phase angle and the auxiliary winding phase angle.
19. The compressor assembly of claim 18 , wherein the control circuit is configured to determine at least one of a rotational speed of the motor and a load of the motor according to the calculated phase difference, the voltage of the main winding and the voltage of the auxiliary winding.
20. The compressor assembly of claim 1 , wherein the control circuit comprises a digital microprocessor.
21. The compressor assembly of claim 1 , wherein the thyristor is a first thyristor, and the assembly further comprises a second thyristor electrically coupled with the second capacitor.
22. A compressor assembly comprising:
a compressor motor coupled to operate a compressor of a heating, ventilation and/or air-conditioning (HVAC) system, the compressor motor including a stator core having a stator yoke and a plurality of teeth extending from the stator yoke toward a central opening, the central opening extending from a first end of the stator core to a second end of the stator core opposite the first end, the plurality of teeth spaced apart from one another and defining a plurality of slots between the plurality of teeth, the compressor motor further including a main winding and an auxiliary winding located within the plurality of slots and wrapped around the plurality of teeth, the main winding coupled to a line terminal to receive power from a line voltage source;
a first capacitor coupled between the line terminal and the auxiliary winding to supply power to the auxiliary winding from the line voltage source;
a second capacitor coupled between the line terminal and the auxiliary winding to supply power to the auxiliary winding from the line voltage source;
a relay coupled between the first capacitor and the line terminal or the auxiliary winding to selectively inhibit the supply of power from the line voltage source to the auxiliary winding via the first capacitor; and
a control circuit coupled to control switching operation of the relay, the control circuit configured to receive at least one of a voltage of the main winding and a voltage of the auxiliary winding, close the relay during an initial startup time period of the compressor motor, subsequently open the relay in response to detection of startup condition criteria, and close the relay in response to detection of excess load condition criteria, the excess load condition criteria including at least one of the received voltages of the main winding and the auxiliary winding.
23. The compressor assembly of claim 22 , wherein the control circuit is configured to, subsequent to closing the relay in response to the detection of the excess load condition criteria, open the relay in response to detection of normal load condition criteria, the normal load condition criteria including at least one of the received voltages of the main winding and the auxiliary winding.
24. The compressor assembly of claim 22 , wherein the control circuit is configured to receive a first current value indicative of a current through the main winding, receive a second current value indicative of a current through the auxiliary winding, and open the relay in response to at least one of the first current value and the second current value exceeding a current overload threshold.
25. The compressor assembly of claim 22 , wherein:
the first capacitor comprises a first capacitor film disposed in an integral multi- capacitor housing; and
the second capacitor comprises a second capacitor film disposed in the integral multi-capacitor housing.
26. A method of controlling a compressor motor assembly, the assembly including a compressor motor having a stator yoke and a plurality of teeth extending from the stator yoke toward a central opening, the central opening extending from a first end of the stator core to a second end of the stator core opposite the first end, the plurality of teeth spaced apart from one another and defining a plurality of slots between the plurality of teeth, the compressor motor further including a main winding and an auxiliary winding located within the plurality of slots and wrapped around the plurality of teeth, the main winding coupled to a line terminal to receive power from a line voltage source, the assembly further including a first capacitor coupled between a line terminal and the auxiliary winding, a second capacitor coupled between the line terminal and the auxiliary winding, a first relay coupled between the first capacitor and the second capacitor, and a second relay coupled between the first capacitor and the auxiliary winding, the method comprising:
opening the first relay and closing the second relay during a run time period of the compressor motor;
receiving a voltage of at least one of the main winding and the auxiliary winding; and
in response to detection of excess load condition criteria including at least the received voltage:
opening the second relay to disconnect the first capacitor from the line terminal or the auxiliary winding;
after a specified voltage balance time period, closing the first relay to couple the first capacitor and the second capacitor in parallel; and
closing the second relay to connect the first capacitor and the second capacitor to the line terminal or the auxiliary winding, to supply power from the line terminal to the auxiliary winding via the first capacitor and the second capacitor.
27. The method of claim 26 , further comprising:
closing the first relay during an initial startup time period of the compressor motor; and
in response to detection of startup condition criteria including at least one of the received voltage and an expiration of the initial startup time period, opening the first relay.
28. The method of claim 26 , further comprising:
receiving a first current value indicative of a current through the main winding;
receiving a second current value indicative of a current through the auxiliary winding; and
opening the second relay in response to at least one of the first current value and the second current value exceeding a current overload threshold.