# US 10,320,313 B2 · Arc free phase control alternatives for AC motor starters

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- Number: US 10,320,313 B2
- Document ID: US10320313B2
- Status: Granted
- Kind: B2
- Application number: 14/643,093
- Filed: 2015-03-10
- Published: 2016-09-15
- Granted: 2019-06-11
- Earliest claimed: 2015-03-10
- Applicants: Young Jun Kim
- Inventors: Young Jun Kim
- Web page: https://patentgrep.com/patent/US10320313B2

## CPC

- H02P 1/04: Means for controlling progress of starting sequence in dependence upon time or upon current, speed, or other motor parameter
- H02P 27/02: using supply voltage with constant frequency and variable amplitude
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

An arc-free phase control circuit for an AC motor that brings about an energy saving effect according to a load change and operates efficiently in terms of cost reduction while securing electrical stability by virtue of an overload protection function. The circuit includes a first relay, a TRIAC, a second relay, a voltage sensing unit, a current sensing unit, a speed voltage sensing unit, a zero-cross point detection unit, and a controller.

## Claims

### Claim 1

An arc-free phase control circuit for an AC motor, comprising:
a first relay for connecting a terminal of an AC power supply source to an AC motor;
a TRIAC for connecting another terminal of the AC power supply source to the AC motor according to a first output terminal signal;
a second relay connected in parallel to the TRIAC and for connecting another terminal of the AC power supply source to the AC motor according to a second output terminal signal;
a voltage sensing unit configured to sense a TRIAC trigger power supply voltage rectified from an output of an isolation transformer with a primary input of a power supply source and output a TRIAC trigger power supply voltage signal to a first input terminal;
a current sensing unit configured to sense a current applied by the AC power supply source and output an applied current signal to a second input terminal;
a zero-cross point detection unit configured to detect a zero-cross point of an AC power supply source and output the zero-cross point to a third input terminal; and
a controller configured to receive the TRIAC trigger power supply voltage, the applied current, the zero-cross point, and the induced voltage from the first to third input terminals, and to phase-control the TRIAC at every half cycle of a commercial frequency,
wherein, when the AC motor is started or stopped according to a stability of the TRIAC trigger power supply voltage of the first input terminal, in order to protect a peripheral circuit from a short circuit accident only at a first time a TRIAC trigger current is allowed, the controller memorizes a zero-crossing time point of an AC power supply voltage and then outputs an ON signal to a first output terminal after a lapse of a certain phase delay time greater than 135° and less than 180° to drive a TRIAC gate so as to apply the current to the TRIAC in a voltage-dropped state, senses the current of the TRIAC which is in a half-wave state through the second input terminal to calculate a circuit impedance and an allowable peak current, and immediately turns off, if a short circuit current is anticipated at a rated AC power supply voltage, so as to protect the peripheral circuit from the short circuit accident within a half cycle, and
wherein, while in a TRIAC mode, the controller receives a coil induced voltage through the third input terminal for a TRIAC-off time and calculates a speed of the AC motor and if the calculated speed is low, then adjusts phase-control a cycle to one third or one fifth of the commercial frequency according to the calculated speed of the AC motor.

### Claim 2 (depends on 1)

The arc-free phase control circuit of claim 1, wherein the arc-free phase control circuit is applied to a three-phase AC motor using:
a first relay combination comprising the first relay connected in series to a first-phase line, a first TRIAC connected in series to a second-phase line, and the second relay connected in parallel to the first TRIAC; and
a second relay combination comprising a third relay connected in series to the second-phase line, a second TRIAC connected in series to a third-phase line, and a fourth relay connected in parallel to the second TRIAC.