Other

Allen-bradley Company, LLC

Buehler Gmbh

Alan W Wilkerson

Thomas A Linke

Troy William Livingston

Issa R Dandan

Ashok K Parida

A drive for controlling the speed of an AC induction motor from an inverter. The inverter applies a voltage to the stator winding of the motor in accordance with the magnitude of a first input signal. The inverter causes the voltage to be applied at a frequency determined by the magnitude of a second input signal to the inverter. The drive includes motor speed sensor and a motor speed reference signal source coupled to a speed regulating amplifier. A slip detector determines the slip of the motor from the speed of the rotor and the energization frequency of the stator winding. A slip regulating amplifier receives the output signal from the speed regulating amplifier and the slip signal and provides an output to a summing amplifier. The summing amplifier also receives a motor speed signal and provides an output. The output comprises the second input signal to the inverter. The output may be supplied through an absolute value circuit as the first input signal to the inverter. Low speed boost and load boost signals may be provided to the first input signal to the inverter. Alternatively, the output of the slip regulating amplifier may be employed as the second input signal to the inverter and to form the first input signal to the inverter.

AC inverter drive

A speed control for controlling the speed of a DC motor provides improved speed regulation during transient loading conditions. The control includes a regulating circuit having an output for controlling the armature voltage to the motor, An input speed reference signal corresponding to the desired speed is provided to the regulating circuit. A feedback signal proportional to armature voltage is also provided to the regulating circuit to establish an error signal for operating the control to regulate the voltage to the motor and therefore the motor speed, An IR compensating circuit provides increased motor voltage when the load increases. The voltage drop due to the armature circuit inductance is measured directly and also utilized to alter the output of the regulator to compensate for the inductive voltage drop occurring under transient loading conditions in a manner tending to establish the speed at the desired speed corresponding to the speed reference signal, during such conditions.

Speed control for controlling the speed of a DC motor

An apparatus and method controls the speed of an AC induction motor by varying the frequency and current to the motor from an inverter power supply. A Counter EMF regulator receives a reference signal corresponding to the desired speed, and a signal proportional to CEMF for feedback. The output of the CEMF regulator is provided to the power supply to control the current to the motor. The CEMF feedback signal is also utilized to vary the output frequency of the power supply in accordance with the magnitude of the CEMF. This maintains the magnetizing component of stator winding current at a constant value for all operating frequencies of the motor. A signal corresponding to the load current component of the stator winding adds to the speed reference signal to the CEMF regulator to increase CEMF and frequency with increasing load, thereby to compensate for increased slip and maintain constant speed. The voltage on a DC bus in the inverter power supply is compared to a reference signal, the magnitude of which corresponds to the voltage on the bus when the motor is operating at synchronous speed. If the bus voltage is less than the reference voltage, the motor is in the motoring condition and the frequency of the power supply is determined by the CEMF. If the bus voltage is greater than the reference voltage, the motor is regenerating, and the frequency of the power supply is increased to prevent regeneration, and to avoid the need for the power supply to absorb regenerative energy.

Speed control for induction motor having improved sensing of motor

An apparatus and method controls the speed of an AC induction motor by varying the frequency and current to the motor from an inverter power supply. A Counter EMF regulator receives a reference signal corresponding to the desired speed, and a signal proportional to CEMF for feedback. The output of the CEMF regulator is provided to the power supply to control the current to the motor. The CEMF feedback signal is also utilized to vary the output frequency of the power supply in accordance with the magnitude of the CEMF. This maintains the magnetizing component of stator winding current at a constant value for all operating frequencies of the motor. A signal corresponding to the load current component of the stator winding adds to the speed reference signal to the CEMF regulator to increase CEMF and frequency with increasing load, thereby to compensate for increased slip and maintain constant speed. The phase displacement between CEMF and stator winding current is determined. If the phase displacement is less than 90.degree., the motor is in the motoring condition and the frequency of the power supply is determined solely by the CEMF. If the phase displacement is greater than 90.degree., the motor is regenerating, and the frequency of the power supply is increased to prevent regeneration, and to avoid the need for the power supply to absorb regenerative energy.

Induction motor speed control having improved sensing of motor operative

A motor control for a treadmill has an improved, inexpensive, and simple set of power supplies, derived from the bus voltages of the DC busses with simple voltage dividers, to supply operational amplifiers connected to the positive DC voltage bus with a dual voltage supply and a common or neutral, and to provide a single voltage power supply connected to the negative bus for the driving circuitry of a motor energization switching controlling element. The dual power supply for the operational amplifiers comprises a voltage divider containing two, series connected zener diodes in series with a resistor. The one of the series connected zener diodes is connected to the positive DC voltage bus, and the resistor is connected to the negative DC voltage bus. A common connection between the two zener diodes becomes the neutral or common voltage for the operational amplifiers, and the zener diode voltages become the positive and negative supply voltages for the amplifiers. The power supply for the driving circuitry of the switch element is structured with a voltage divider comprising one zener diode and a series connected resistor. In this case, the zener diode is connected to the negative bus and the resistor to the positive bus. Isolation between the two power supplies is accomplished with optical, capacitive, or transformer isolation. The regulating circuit of the motor control may include circuitry for compensation for the inductance voltage drop in the armature circuit of the motor.

Motor control for a treadmill having improved power supply and improved

A control for energizing a DC motor to provide improved speed regulation to the motor under transient conditions. The control includes a regulating circuit having an output signal controlling the armature voltage applied to the motor. An input speed reference signal corresponding to the desired speed of said motor is provided to the regulating circuit. An input armature voltage feedback signal is also provided to the regulating circuit to produce an error signal for operating said regulating circuit to establish the armature voltage, and hence the speed of said motor. The armature current of the motor is sensed and a signal corresponding to the voltage drop resulting from the inductance of the armature circuit provided to the regulating circuit for altering the output of the regulating circuit in a manner tending to establish the speed of said motor at that established by said speed reference signal. An IR compensating circuit provides an IR compensating signal to the regulating circuit.

Motor control having improved speed regulation under intermittent loading

A controller for controlling currents in an AC line connected to the controller is capable of causing the controlled current to assume any pre-determined magnitude and wave form. The pre-determined AC magnitude and wave form need not be of the same frequency or wave form existing at AC power lines connected to the controller. The controller uses the voltage at the AC power lines and an additional DC voltage as two sources of power to control the current in an inductor connected in series with the AC lines. A plurality of electronic switches are arranged so that at any instant in time, closing of appropriate switches will apply either the line voltage, or the sum of the line voltage and the DC voltage, or the difference between the line voltage and the DC voltage to the inductor. This causes the current of the inductor to increase or decrease at a rate determined by the net applied voltage. Because of the two sources of power, either a positive or negative voltage is available at any time for connection to the inductor. Modulation of the switches provides a time varying average voltage across the inductor that results in the desired time varying inductor current which, due to its series connection is also the AC line current. Applications of the controller include control of power factor, at unity or any desired lagging or leading level, neutralizing of harmonic line currents, and recovery of power generating externally of the controller by feeding regenerative current back to the AC power lines.

AC line current controller utilizing line connected inductance and DC

A saw apparatus comprises an operatable saw blade and a holding arm for gripping an object to be sawed, plus means for moving the saw blade and holding arm together to cause the saw blade to engage the object for sawing under controlled-pressure conditions. The saw blade is carried by strain gauge means, the strain gauge means being part of electronic means for sensing the load of the operatable saw blade on the strain gauge means. Thus, pressure of the object for sawing against the top of the saw blade causes an increase in the load sensed by the strain gauge. The electronic signal generated thereby may be used in a feedback system to control the pressure of the workpiece against the saw blade.

Precision cutter with automated pressure control

A non-contact ammeter for measuring direct current in a conductor has a core capable of carrying a magnetic flux. The core surrounds the conductor so that the latter serves as a primary winding for the core. A second winding on the core is inductively coupled to the conductor. A current indicator is connected to the second winding. A control establishes the voltage on the second winding and flux changes in the core to avoid or limit saturation of the core. The control may be responsive to the flux condition of the core.

Non-contact ammeter

Apparatus for polishing or grinding specimens in which the pressure between the sample and the platen against which it presses for grinding or polishing is controlled by a feedback system, which includes a strain gauge from which the sample-holding grinding shaft is suspended.

Polishing apparatus

A direct current motor control circuitry provides linearity between an input signal to the circuitry and torque developed in the motor energized by the circuitry. A signal divider algebraically divides a numerator signal by a denominator signal and provides a quotient signal as the output. The input signal is provided to the signal divider as the numerator signal. A field circuit energizes the field winding of the motor. An armature circuit energizes the armature winding. One of the field or armature circuit provides a signal proportional to the respective one of field current or armature current to the denominator input of the signal divider. The signal divider is connected to the other of the field circuit or armature circuit for establishing the field current or armature current in accordance with the output quotient signal.

Motor torque control with improved linearity

An energy utilization circuit and method energizes a.c. loads with a.c. power of conventional voltage and frequency characteristics. A coverter responsive to an energy source, typically a wind or solar driven generator, converts the energy to d.c. electrical power. An inverter alters the d.c. power to a.c. power. An a.c. wave generator, such as an alternator, is connected to the output of the inverter. The alternator is operated to impress its voltage and frequency on the output of the inverter so as to lend conventional characteristics to this output. Excess power from the inverter maintains the operation of the alternator.

Energy utilization circuit and method

A power maximization circuit periodically samples the output power of a power supply to regulate output voltage or current toward that resulting in maximum output power. Power increasing variations in voltage or current are continued until maximum power is reached and exceeded, at which time the direction of variation is reversed until operation becomes stabilized at maximum power conditions. The circuit includes a sampling means for periodically sampling the output power. The sampling means is connected to a comparison means providing an output signal, the condition of which is indicative of whether the power at any given sampling period is greater or less than the previous sampling period. Means are provided for detecting on a coincidence basis, the condition of the comparison means output signal and for altering the magnitude of the current or voltage of the power supply toward that which obtains maximum power.

Power maximization circuit

A watt meter circuit capable of providing an electrical signal indicative of power includes a signal forming means for providing a pair of signals proportional to current. The signals are equal to each other in magnitude but opposite in polarity and are provided in parallel through a switch to filter which provides the electrical power signal. The switch is operated by a signal generating means which generates a triangular wave form. The voltage to the watt meter is compared with the triangular wave form to vary the duty cycle of the switch and the magnitude and polarity of the output signal in accordance with the algebraic product of voltage and current.

Watt meter providing electrical signal proportional to power

A switching circuit, typically a thyristor bridge, is connected to a source of waste energy. The source can be waste energy occurring as a by-product of man's activities such as waste heat energy, stored water, or the potential mechanical energy of elevated objects. The source provides d.c. power either directly or through conversion. The switching circuit is also connected to an a.c. load and across a.c. power mains energizing the load. The switching circuit is operable to periodically connect the waste energy source to the a.c. load in a power supplying manner. The a.c. mains impart suitable voltage and frequency characteristics to the electrical power so supplied. In the event the supplied power exceeds the power required by the a.c. load, the difference is taken by the a.c. power mains.

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Cedarburg, WI, United States of America

Alan W Wilkerson