COMPRESSOR VOLTAGE PROTECTION MODULE ENABLING BASED ON SOFT STARTER DETECTION

A heating ventilation and air-conditioning system is disclosed and includes: at least one analog-to-digital converter configured to sample a voltage signal on or across one or more power lines to provide samples, the one or more power lines supplying power to a compressor; a voltage-based protection module configured to execute one or more voltage-based protection algorithms to protect the compressor; and a soft starter detection module configured, based on the samples, to detect i) presence of a soft starter, and ii) activity of the soft starter ramping up current to the compressor, and to, based on detecting the presence of the soft starter and the activity of the soft starter, disable voltage-based protection provided by the voltage-based protection module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of Indian Patent Application No. 202221050278 filed Sep. 2, 2022. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure relates to voltage protection modules for compressors of heating, ventilation and air-conditioning (HVAC) systems.

BACKGROUND

Compressor protection modules in HVAC systems protect compressors from various faults. Some example compressor protection modules include a positive temperature coefficient (PTC) based motor protection module, a negative temperature coefficient (NTC) based scroll over temperature protection module, a reverse phase protection module, a single phasing protection module, over and under voltage protection modules, a phase imbalance protection module, frequency supply over and under range protection modules, and a compressor short cycling protection module. The PTC based motor protection module and the NTC based scroll over temperature protection module prevent compressor overheating events. The reverse phase protection module prevents reverse rotation of a compressor.

The single phasing protection module prevents the compressor from operating when a phase of the compressor is lost. The over and under voltage protection modules prevent the compressor from operating when voltages are above or below predetermined safe voltage operating ranges. The phase imbalance protection module prevents the compressor from operating when the phases of the compressor are unbalanced such that voltages of one phase are less than voltages of another phase. The frequency supply over and under range protection modules prevent the compressor from operating when the frequency of power supplied to the compressor is not within a predetermined safe operating range. The compressor short cycling protection module prevents the compressor from operating when a cooling cycle of the compressor is reduced causing the compressor to turn ON and OFF more often, which can degrade the compressor.

SUMMARY

A heating ventilation and air-conditioning system is disclosed and includes: at least one analog-to-digital converter configured to sample a voltage signal on or across one or more power lines to provide samples, the one or more power lines supplying power to a compressor; a voltage-based protection module configured to execute one or more voltage-based protection algorithms to protect the compressor; and a soft starter detection module configured, based on the samples, to detect i) presence of a soft starter, and ii) activity of the soft starter ramping up current to the compressor, and to, based on detecting the presence of the soft starter and the activity of the soft starter, disable voltage-based protection provided by the voltage-based protection module.

In other features, the soft starter detection module is configured to: disable the voltage-based protection provided by the voltage-based protection module during a soft start ramp up period; and enable the voltage-based protection provided by the voltage-based protection module in response to detecting an end of the soft start ramp up period.

In other features, the soft starter detection module is configured to: detect whether the voltage signal is a chopped voltage signal; in response to detecting that the voltage signal is a chopped voltage signal, determine that the soft starter is ramping up current to the compressor; and in response to detecting that the voltage signal is not a chopped voltage signal, determine that the soft starter is not ramping up current to the compressor.

In other features, the soft starter detection module is configured to: determine a first root mean square voltage of the voltage signal; determine a second root mean square voltage of the voltage signal; based on a difference between the first root mean square voltage and the second root mean square voltage, determine whether the soft starter is ramping up the current to the compressor; and disable the voltage-based protection provided by the voltage-based protection module in response to determining that the soft starter is ramping up the current to the compressor.

In other features, the soft starter detection module is configured to: determine the first root mean square voltage-based on a square root of an average sum of squares of the samples of the voltage signal; and determine the second root mean square voltage-based on a peak of the samples of the voltage signal divided by a square root of 2.

In other features, the soft starter detection module is configured to: track an amount of time during a startup of the compressor that the soft starter is ramping up current to the compressor; compare the amount of time to a maximum ramp time; and based on the comparison of the amount of time and the maximum ramp time, enable the voltage-based protection provided by the voltage-based protection module.

In other features, the soft starter detection module is configured to: in response to the amount of time being longer than the maximum ramp time, enable the voltage-based protection provided by the voltage-based protection module; and in response to the amount of time being less than or equal to the maximum ramp time, maintaining the voltage-based protection module in a disabled state.

In other features, the soft starter detection module is configured to: determine a peak voltage of the samples; determine a present partial sum of the samples; determine an accumulated partial sum based on the present partial sum; determine a first voltage-based on the accumulated partial sum; determine a second voltage-based on the peak voltage; and based on the first voltage and the second voltage, detect at least one of i) the presence of a soft starter, and ii) the activity of the soft starter ramping up current to the compressor.

In other features, the soft starter detection module is configured to: determine a first voltage-based on a square root of an averaged sum of squares of the samples; determine a second voltage-based on a peak voltage of the samples; and based on the first voltage and the second voltage, detect at least one of i) the presence of a soft starter, and ii) the activity of the soft starter ramping up current to the compressor.

In other features, the heating ventilation and air-conditioning system further includes: the soft starter; the compressor; a contactor connected between the soft starter and the compressor; and a control module configured to close the contactor to supply current from the soft starter to the compressor.

In other features, the control module is configured to enable the at least one analog-to-digital converter to sample the voltage signal subsequent to closing the contactor.

In other features, the one or more power lines are either i) supplying power from the soft starter to the contactor, or ii) supplying power from the contactor to the compressor.

In other features, a soft starter detection method for a heating ventilation and air-conditioning system is disclosed. The heating ventilation and air-conditioning system includes a voltage-based protection module configured to execute one or more voltage-based protection algorithms to protect a compressor. The method includes: sampling a voltage signal on or across one or more power lines to provide samples, the one or more power lines supplying power to the compressor; based on the samples, i) detecting presence of a soft starter supplying the power to the compressor, and ii) detecting activity of the soft starter ramping up current to the compressor; and based on detecting the presence of the soft starter and the activity of the soft starter, disabling voltage-based protection provided by the voltage-based protection module.

In other features, the soft starter detection method further includes: disabling the voltage-based protection provided by the voltage-based protection module during a soft start ramp up period; and enabling the voltage-based protection provided by the voltage-based protection module in response to detecting an end of the soft start ramp up period.

In other features, the soft starter detection method further includes: detecting whether the voltage signal is a chopped voltage signal; in response to detecting that the voltage signal is a chopped voltage signal, determining that the soft starter is ramping up current to the compressor; and in response to detecting that the voltage signal is not a chopped voltage signal, determining that the soft starter is not ramping up current to the compressor.

In other features, the soft starter detection method further includes: determining a first root mean square voltage of the voltage signal; determining a second root mean square voltage of the voltage signal; based on a difference between the first root mean square voltage and the second root mean square voltage, determining whether the soft starter is ramping up the current to the compressor; and disabling the voltage-based protection provided by the voltage-based protection module in response to determining that the soft starter is ramping up the current to the compressor.

In other features, the soft starter detection method further includes: determining the first root mean square voltage-based on a square root of an average sum of squares of the samples of the voltage signal; and determining the second root mean square voltage-based on a peak of the samples of the voltage signal divided by a square root of 2.

In other features, the soft starter detection method further includes: tracking an amount of time during a startup of the compressor that the soft starter is ramping up current to the compressor; comparing the amount of time to a maximum ramp time; and based on the comparison of the amount of time and the maximum ramp time, enabling the voltage-based protection provided by the voltage-based protection module.

In other features, the soft starter detection method further includes: in response to the amount of time being longer than the maximum ramp time, enabling the voltage-based protection provided by the voltage-based protection module; and in response to the amount of time being less than or equal to the maximum ramp time, maintaining the voltage-based protection module in a disabled state.

In other features, the soft starter detection method further includes: determining a peak voltage of the samples; determining a present partial sum of the samples; determining an accumulated partial sum based on the present partial sum; determining a first voltage-based on the accumulated partial sum; determining a second voltage-based on the peak voltage; and based on the first voltage and the second voltage, detecting at least one of i) the presence of a soft starter, and ii) the activity of the soft starter ramping up current to the compressor.

In other features, the soft starter detection method further includes: determining a first voltage-based on a square root of an averaged sum of squares of the samples; determining a second voltage-based on a peak voltage of the samples; and based on the first voltage and the second voltage, detecting at least one of i) the presence of a soft starter, and ii) the activity of the soft starter ramping up current to the compressor.

In other features, the soft starter detection method further includes: closing a contactor to supply current from the soft starter to the compressor; and enabling sampling of the voltage signal subsequent to closing the contactor.

In other features, the one or more power lines either i) supply power from the soft starter to the contactor, or ii) supply power from the contactor to the compressor.

DETAILED DESCRIPTION

In HVAC systems, compressors are often driven with soft starters to minimize the amount of inrush current experienced by the compressors during startup. Soft starters are also used to minimize voltage flickering on power lines supplying power to the compressors. A soft starter produces a chopped waveform, as shown inFIG.1, while ramping up current during a startup of a compressor.FIG.1shows a voltage signal100out of a soft starter having a chopped waveform including irregular portions102. The soft starter may provide a 3-phase output with three voltage signals or a single-phase output with a single voltage signal, depending on the type of compressor (i.e., 3-phase or single-phase compressor). One or more of the voltage signals may have a chopped (or distorted) waveform. The voltage signal100ofFIG.1may represent, for example, the output of a single-phase soft starter, one or more phases of a 3-phase soft starter, or a voltage measured across two phases of an output of a 3-phase soft starter.

Due to a chopped waveform of a voltage signal, a voltage-based protection module monitoring the voltage signal may generate one or more nuisance faults. Example nuisance faults (or false positives) are a missing phase fault, a reverse phase fault, an undervoltage fault, a supply frequency out of range fault, etc. This is because different points of the voltage signals are sampled. Due to the chopped or irregular nature of the corresponding waveforms of the voltage signals, the voltage-based protection module can behave inappropriately and generate the nuisance faults. As an example, chopped voltage signals having irregular portions may be sampled. The samples may then be evaluated by voltage-based protection algorithms executed by the voltage-based protection module. The calculations performed by these algorithms are based on the samples, which can result in false positives with regards to detecting faults. For example, if there is a 25% phase-to-phase deviation between samples of different phase voltage signals, then a corresponding voltage-based protection module may detect a fault due to the sampling of chopped (or irregular) portions of the voltage signals. The voltage-based protection module, based on the fault, may then shut OFF the corresponding compressor.

The examples set forth herein include an HVAC system that includes a protection module including a voltage-based protection module and a soft starter detection module. The soft starter detection module detects active presence (or ramping activity) of a soft starter and absence of the soft starter during startup periods of a compressor. The soft starter detection module enables and disables the voltage-based protection module based on the active presence and absence of the soft starter. This prevents false positives during startup. The soft starter detection module disables the voltage-based protection module for the period of time when the soft starter is ramping up current to the compressor.

The ramp up time of a compressor is not consistent and thus can vary.FIG.2shows a stepped waveform illustrating example OFF and ON periods of a compressor including actual ramp up periods during startup of the compressor. A first compressor ON period200is shown having a first ramp up period202. The compressor is turned OFF and then turned back ON. A second compressor ON period204is shown having a second ramp up period206. The second ramp up period206is shorter than the first ramp up period202. In order to disable the voltage-based protection module for the duration of any ramp up period, the voltage-based protection module may be disabled for a maximum ramp up period during each startup, where each ramp up period has the same or a shorter duration than the maximum ramp up period. However, if voltage-based protection is disabled for the maximum ramp up period, then as can be seen inFIG.2, there are intermediate unprotected periods210,212during which the current of the compressor is up (e.g., above a predetermined level) and/or no longer increasing and voltage-based protection is disabled. This occurs between i) the current ramped up periods and ii) the points in time when the maximum ramp up periods end and voltage-based protection is enabled. Voltage-based protection is not provided during the intermediate unprotected periods210,212.

Maintaining the disablement of voltage-based protection for a maximum soft start ramp time can also result in erratic behavior by a protection module executing voltage-based protection algorithms. This may occur, for example, when a system operator sets a soft starter ramp time to be greater than the maximum soft start ramp time. In this situation, a period exists when the current to the compressor is still being ramped up and thus a soft starter is still providing a chopped waveform and voltage-based protection is enabled. As another example, due to load variations, a soft starter ramp time may be less than the maximum soft starter ramp time. As a result, the voltage-based protection algorithms remain inactive for the maximum soft starter ramp time and an intermediate unprotected period exists, which can negatively affect life of motor windings in case of a voltage-based fault occurring during the unprotected intermediate period.

In order to eliminate the described intermediate unprotected periods210,212, the soft starter detection module may not disable the voltage-based protection module for a maximum amount of ramp time, but rather for an actual amount of ramp time. The soft starter detection module detects (i) when the soft starter is actively ramping up the current and thus is providing a chopped voltage signal output, and (ii) when the soft starter stops actively ramping up the current and thus provides a voltage signal output that is not chopped. The soft starter detection module disables voltage protection during the ramp up period and enables voltage protection at the end of the ramp up period.

FIG.3shows a HVAC system300including a soft starter module302, a contactor304, a compressor306and a HVAC control module308. The soft starter module302may be referred to as a soft starter and receives utility power. The utility power may be in the form of 3-phase power provided via lines L1, L2, L3. The soft starter302supplies the 3-phase voltage output signals represented by lines310to the contactor304. Although the soft starter302is shown as a 3-phase soft starter, the soft starter302may be implemented as a single-phase soft starter and output a single phase voltage signal instead of 3-phase voltage signals. During startup of the compressor306, the soft starter302ramps up current supplied to the contactor304via the lines310. Startup of the compressor306refers to when the compressor306is turned ON and current to the compressor306is ramped up from zero current to a predetermined current level.

The contactor304may be implemented as a relay and include a coil320that is energized to close the contactor304and transfer power from the lines310to lines322, which supply power to the compressor306. The power supplied via the lines322may be provided to a motor330of the compressor306. The compressor306may further include sensors332and a compressor control module334. The compressor control module334may operate the motor330based on outputs of the sensors332. The sensors332may include voltage sensors, current sensors, temperature sensors, and/or other sensors.

The HVAC control module308controls operation of the contactor304and the compressor306. The HVAC control module308may include analog-to-digital (A/D) converters340,342,344and a protection module346. The protection module346controls state of the coil320and as a result ON and OFF states of the contactor304and ON and OFF states of the motor330of the compressor306. The protection module346may include a voltage-based protection module350, a soft starter detection module352, a NTC based scroll protection module354and a PTC based motor protection module356. The A/D converters340,342,344convert analog voltage signals to digital voltage signals. The analog voltage signals may be the voltage signals on the lines322, as shown, or may be voltage signals on lines310. The A/D converters340,342,344sample the analog voltage signals and provide the samples to the modules350,352. The modules354,356may operate based on outputs of the sensors332.

The soft starter detection module352enables and disables the voltage-based protection module350based on detection of active ramping up of current by the soft starter302to the compressor306. The soft starter detection module352detects the installation (or presence) of the soft starter302and whether the soft starter302is actively ramping up current based on the samples from the A/D converters340,342,344. This allows the soft starter detection module352and the protection modules350,354,356to be compatible with HVAC systems that do include a soft starter and HVAC systems that do not include a soft starter. The modules350,354,356implement corresponding protective algorithms362, which may be stored in memory360, such as a reverse phase protection algorithm, a single phasing protection algorithm, over and under voltage protection algorithms, a phase imbalance protection algorithm, a frequency supply over and under range protection algorithms, a compressor short cycling protection algorithm, a PTC based motor protection algorithm, and a NTC based scroll over temperature protection algorithm. The memory may also store a soft starter algorithm364that is implemented by the soft starter detection module352for detecting ramping up of current to the compressor306and disabling and enabling the voltage-based protection based on this detection. The soft starter algorithm364does not conflict with the protective algorithms362and hence the protection module346does not perform erratically.

The protection module346and/or the soft starter detection module352may include counters370, such as a soft starter present counter and a soft starter absent counter. The soft starter present counter is used to confirm, during a startup event of the compressor306, that the soft starter302is actively ramping up current. The soft starter absent counter is used to confirm, during a startup event of the compressor306, that the soft starter has completed ramping up the current. The protection module346and/or the soft starter detection module352may also include a soft starter ramp timer372. The soft starter ramp timer372is used to determine ramp time of the soft starter. If the ramp time exceeds a set amount of time (e.g., 0.5-2.0 seconds), the soft starter detection module352and/or the protection module346may override operation of the soft starter detection module352and enable the voltage-based protection module350. This assures that the voltage-based protection modules350and implementation of the corresponding stated algorithms are not disabled for too long and/or an indefinite amount of time.

When the protection module346detects a fault, for example, via one or more of the modules350,354,356and/or via one or more of the algorithms implemented by the modules350,354,356, the protection module346de-energizes (or opens) the contactor304. When voltage-based protection is disabled during an initial startup period, the protection module346may de-energize the contactor304if one or more of the modules354,356detects a fault. The protection module346may not de-energize the contactor304if the voltage-based protection module350is not completely disabled and detects a fault during the initial startup period when voltage-based protection is disabled. If a soft starter is not incorporated in the HVAC system300, then voltage-based protection is enabled during startup of the compressor306.

FIG.4shows a plot of compressor ON and OFF periods including actual ramp up periods during startup of the compressor. A first compressor ON period400is shown having a first ramp up period402. The compressor is turned OFF and then turned back ON. A second compressor ON period404is shown having a second ramp up period406. The second ramp up period406is shorter than the first ramp up period402. Voltage-based protection is disabled for the ramp up periods402,406and is enabled when the ramp up periods402,406are over. As can be seen, voltage-based protection is disabled for shorter periods of time than a maximum ramp up time. The voltage-based protection may be disabled for the maximum ramp up time if the actual ramp up period extends to the end of the maximum ramp up period. This minimizes the periods of time for which compressor protection algorithms are disabled. The disabled periods are the shorter of i) the periods of soft starter ramp up activity, and ii) the maximum ramp up period.

The soft starter detection module352ofFIG.3may monitor a three-phase voltage signal at each powerup of the compressor306. The three-phase voltage signal refers to collectively the voltage signals on the lines310or322, which each carry a respective single phase voltage signal. The soft starter302produces a chopped voltage signal waveform on one or more phases of the three-phase voltage signal to reduce inrush current during initial start periods of the compressor. Any of the three phase voltage signals may be monitored. The lines310may be referred to as L1′, L2′ and L3′, respectively. The lines322may be referred to as L1″, L2″, and L3″, respectively. In addition, or alternatively, voltages between the three phase voltage signals may be monitored and sampled by the A/D converters340,342,344. For example, a L1′-L2′ voltage, a L2′-L3′ voltage, a L1′-L3′ voltage, a L1″-L2″ voltage, a L2″-L3″ voltage, and/or a L1″-L3″ voltage may be monitored and sampled.

FIGS.5A and5B(collectivelyFIG.5) shows a soft starter detection method. The method may be performed by the HVAC control module308and the modules and devices thereof. This method may be implemented each time a compressor is being started (or turned ON). The HVAC control module308ofFIG.3may control the turning ON of the compressor306and may signal the soft starter when the compressor is to be turned ON. The HVAC control module308may also control timing of when the soft starter is to provide a chopped waveform to ramp up current to the compressor. At500, the HVAC control module308may turn ON the protection module346.

At502, the protection module346may determine whether the contactor304is in a closed (or ON) state (e.g., the coil320is energized). If yes, operation504is performed. At powerup, the protection module346turns ON the contactor304. At504, the protection module346enables the soft starter detection module352.

At506, the protection module346and/or the soft starter detection module352starts the soft starter ramp timer372. At508, the soft starter detection module352may initialize and/or set a partial sum, a partial sum counter, a present partial sum, a soft starter present counter, and a soft starter absent counter equal to zero.

At510, the soft starter detection module352obtains a predetermined number of instantaneous voltage samples of one or more power line signals from one or more A/D converters (e.g., one or more of the A/D converters340,342,344). In one embodiment, a single phase or a voltage across two phases is monitored. In another embodiment, two phases or two voltages across two pairs of phases are monitored. As an example, one of the voltage signals on one of the lines322may be monitored and 25 microseconds (μs) of samples of the one of the voltage signals may be collected. This may include collecting 80 samples over the 25 μs period.

At512, the soft starter detection module352may calculate a peak voltage of the voltage signal based on the predetermined number of samples and store the peak voltage in a memory (e.g., the memory360) or other storage device (e.g., a register or a buffer of the soft starter detection module352). As an example, the peak voltage VPmay be determined according to equation 1, where S1-SN are the samples, and N is the number of samples.

At514, the soft starter detection module352may calculate the present partial sum PPS. This may be done according to equation 2.

At516, the soft starter detection module352may determine whether the partial sum counter is equal to a predetermined value (e.g., 50). If not, operation518may be performed, otherwise operation522may be performed.

At518, the soft starter detection module352may calculate an accumulated partial sum, which may be equal to a sum of the present partial sum PPS and the partial sum PS (or last accumulated partial sum value). At520, the soft starter detection module352may increment the partial sum counter. For example, the partial sum counter value may be set equal to the partial sum counter value plus one. Operation510may be performed subsequent to performing operation520.

At522, the soft starter detection module352may calculate a first root mean square (RMS) voltage RMS1based on the accumulated partial sum PS. For example, RMS1may be calculated using equation 3.

By performing operations510,512,514,516,518,520, RMS1is calculated every predetermined period of time (e.g., 100 milliseconds (ms)=80×50×25 μs), where 80 is the number of samples obtained for each of 50 iterations.

At524, the soft starter detection module352may reset the partial sum (or accumulated partial sum), partial sum counter, and the present partial sum to zero. Operation526is performed subsequent to operation524.

At526, the soft starter detection module352may calculate a second RMS voltage RMS2based on the peak voltage. This peak voltage may be a peak voltage determined during a last iteration of operation512or may be a peak of the peak voltages determined during the last set of iterations of operations510,512,514,516,518,520. For example, the peak voltage may be the greatest of the 51 iterations of peak voltages determined during iterations of operations510,512,514,516,518,520, when the predetermined iteration value is equal to 50. RMS2may be calculated using equation 4. In one embodiment, at least operations512,522and526are repeated for a predetermined period of time each time the compressor306is turned ON. The predetermined period may be 5 seconds or less. As an example, the predetermined period may be 400 ms.

At528, the soft starter detection module352may determine whether an absolute difference between RMS1and RMS2is less than a predefined value (e.g., 5 V). The predefined value may be referred to as an empirical offset value. If yes, operation530may be performed, otherwise operation540may be performed. In an embodiment, soft starter absence is detected when RMS2is less than or equal to a sum of RMS1and the predetermined empirical offset value. These determinations may be made to determine if a waveshape of the voltage signal being monitored is sinusoidal. When the voltage signal is sinusoidal and not chopped, absence of soft starter activity to ramp up current is detected.

At530, the soft starter detection module352may increment the soft starter absent counter. At532, the soft starter detection module352may determine whether the soft starter absent counter is equal to a first predetermined threshold (e.g., 4) or other predetermined threshold. In an embodiment the first predetermined threshold is greater than or equal to 1. If no, operation510may be performed, otherwise operation534may be performed.

At534, the soft starter detection module352may set a flag in memory indicating that soft starter absence is confirmed. Soft starter absence may refer to a soft starter not being incorporated in the HVAC system300and/or the soft starter302not ramping up current to the compressor306. This indicates that the soft starter302has finished ramping up current to the compressor306. In one embodiment, soft starter absence is determined when RMS1is equal to RMS2. In another embodiment, soft starter absence is determined when the absolute difference between RMS1and RMS2is less than or equal to the predetermined empirical offset value. At536, the soft starter detection module352may reset the soft starter absent counter to zero.

At538, the soft starter detection module352may enable the voltage-based protection module350and/or implementation of voltage-based protection algorithms, such as the reverse phase protection algorithm, single phasing protection algorithm, over and under voltage protection algorithms, phase imbalance protection algorithm, frequency supply over and under range protection algorithms, and compressor short cycling protection algorithm. This may include allowing the voltage-based protection module350to turn OFF the compressor when one or more of the voltage-based protection algorithms detect a fault. In one embodiment, as soon as the soft start period of ramping up current to the compressor306is over, the soft starter detection module352enables the voltage-based protection.

At540, the soft starter detection module352may determine whether RMS2is greater than a sum of RMS1and the predefined value (e.g., 5V). If no, operation542may be performed, otherwise operation546may be performed. This determination is made to determine if a waveshape of the voltage signal being monitored is chopped for an initial portion of a startup period. When the voltage signal is chopped, presence of soft starter activity to ramp up current is detected.

At542, the soft starter detection module352may determine whether RMS1is greater than a sum of RMS2and the predefined value (e.g., 5V). In one embodiment, the predefined value is 0V. In another embodiment, the predetermined value is less than 5V. If yes, operation544is performed.

At544, the soft starter detection module352may set a flag indicating a calculation error has occurred. In the event of a calculation error, the values of RMS1and RMS2may be discarded. Operation554may be performed subsequent to operation544.

At546, the soft starter detection module352may increment the soft starter present counter. At548, the soft starter detection module352may determine whether the soft starter present counter is equal to a second predetermined threshold (e.g., 4) or other predetermined threshold. In an embodiment, the second predetermined threshold is greater than or equal to 1. The second predetermined threshold may be the same or different than the first predetermined threshold. If no, operation510may be performed, otherwise operation550may be performed. By performing operations532and548, RMS1and RMS2are confirmed every predetermined period of time (e.g., 4×100 ms or 400 ms, where 4 is the first and/or second predetermined threshold). In an embodiment, the second predetermined threshold is different than the first predetermined threshold.

At550, the soft starter detection module352may set a flag indicating soft starter presence is confirmed and disable voltage-based protection. Soft starter presence may refer to the HVAC system300including the soft starter302and the soft starter302ramping up current to the compressor306. This may include disabling the voltage-based protection module350and/or preventing voltage-based protection operations from being performed. Execution of voltage-based protection algorithms may be prevented. At552, the soft starter detection module352may reset the soft starter present counter to zero.

At554, the soft starter detection module352may determine whether the soft starter ramp time is greater than the maximum ramp time. The max ramp time may be set based on a type of load and/or size of the compressor306. In one embodiment, the maximum ramp time is not more than 10 seconds. If yes, operation556may be performed, otherwise operation510may be performed. The soft starter ramp time is the current amount of time that the soft starter302has been ramping up current to the compressor306from the point in time when the compressor was last turned ON.

At556, the soft starter detection module352may set a flag indicating a soft starter ramp timeout has occurred. Operation538may be performed subsequent to performing operation554. The method may end subsequent to performing operation538.

The above-described examples include enabling protection modules and implementation of protection algorithms when soft starter action of ramping up current to a compressor is over, thereby avoiding exposure of compressor motor windings to high current levels due to faults, such as high current level experienced during a single phasing fault. The soft starter algorithm implemented by performing the above-described method is used to detect the end of a ramp up period regardless of a length of the ramp up period. The examples disclosed herein are implementable independent of soft starter current rating and regardless of soft starter make or model. The voltage-based protection is disabled independent of maximum ramp period, which may be set by a system operator.