Method of limiting motor power output

Claim 1

A method of controlling the power output of a variable speed motor operating to drive a device under variable load conditions comprising the steps of: (a) driving a representative device by operating said representative motor over a range of speeds and sensing parameters to determine the relationship of representative motor speed to work output of said representative device; (b) driving said representative device with said motor operating at maximum power conditions over a range of variable load conditions, and sensing parameters to determine the work outputs and the corresponding speeds and power outputs of said representative motor over said range; (c) establishing a particular power output limit for the motor; (d) using the above determinations to calculate the maximum allowable motor speeds corresponding to said power output limit over said range of variable load conditions; (e) sensing the actual speed of the variable speed motor driving the device under variable load conditions; and (f) limiting said actual speed to said maximum allowable motor speeds while operating within said range of variable load conditions.

Claim 2

A method of controlling the power output of a variable speed motor operating to drive a device under variable load conditions comprising the steps of: (a) driving a representative device by operating said representative motor over a range of speeds and sensing parameters to determine the relationship of representative motor speed to work output of said representative device; (b) driving said representative device with said motor operating at maximum power conditions over a range of variable load conditions, and sensing parameters to determine the work outputs and the corresponding speeds and power outputs of said representative motor over said range; (c) establishing a particular power output limit for the motor; (d) using the above determinations to calculate the maximum allowable motor speeds corresponding to said power output limit over said range of variable load conditions; (e) sensing the actual speed of the variable speed motor driving the device under variable load conditions; and (f) limiting said actual speed to said maximum allowable motor speeds while operating within said range of variable load conditions.

Claim 8

A method of limiting the power output of a variable speed motor which is applied to drive a fan comprising the steps of: (a) operating a representative motor and fan combination and sensing parameters to determine the volume flow rates of said representative fan as a function of said representative motor speeds; (b) operating said representative motor and fan combination and sensing parameters to determine, for various static pressure conditions of said representative fan, with said representative motor operating under maximum power conditions, the volume flow rate of said representative fan and the corresponding speeds and power outputs of said representative motor; (c) establishing a particular power output limit for the motor; (d) using the known fan law relationship of motor speed and power output, determining the maximum motor speeds corresponding to said power output limit for each of said various static pressure conditions; (e) using the volume flow rates and motor speeds obtained in step (a) and using the known fan law relationship of speed versus volume flow rate, determining reference speeds for each of said various static pressure conditions; (f) using the maximum motor speeds and the reference speeds obtained in respective steps (d) and (e), establishing a best fit straight line equation to express the maximum allowable motor speeds as a function of said reference speeds; (g) sensing the actual speed of the variable speed motor driving the fan; and (h) limiting said control speeds to said maximum allowable motor speeds found in step (f).

Claim 9

A method of limiting the power output of a variable speed motor which is applied to drive a fan comprising the steps of: (a) operating a representative motor and fan combination and sensing parameters to determine the volume flow rates of said representative fan as a function of said representative motor speeds; (b) operating said representative motor and fan combination and sensing parameters to determine, for various static pressure conditions of said representative fan, with said representative motor operating under maximum power conditions, the volume flow rate of said representative fan and the corresponding speeds and power outputs of said representative motor; (c) establishing a particular power output limit for the motor; (d) using the known fan law relationship of motor speed and power output, determining the maximum motor speeds corresponding to said power output limit for each of said various static pressure conditions; (e) using the volume flow rates and motor speeds obtained in step (a) and using the known fan law relationship of speed versus volume flow rate, determining reference speeds for each of said various static pressure conditions; (f) using the maximum motor speeds and the reference speeds obtained in respective steps (d) and (e), establishing a best fit straight line equation to express the maximum allowable motor speeds as a function of said reference speeds; (g) sensing the actual speed of the variable speed motor driving the fan; and (h) limiting said control speeds to said maximum allowable motor speeds found in step (f).