# US 8,542,506 B2 · Method and apparatus for controlling the power of a transformer using a soft start circuit

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- Number: US 8,542,506 B2
- Document ID: US8542506B2
- Status: Granted
- Kind: B2
- Application number: 12/590,911
- Filed: 2009-11-16
- Published: 2011-05-19
- Granted: 2013-09-24
- Earliest claimed: 2009-11-16
- Assignees: Middle Atlantic Products, Inc.
- Applicants: Robert Schluter; Bernard P. O'Kane; Brendan K. Walsh; Steve Kaufer
- Inventors: Robert Schluter; Bernard P. O'Kane; Brendan K. Walsh; Steve Kaufer
- Web page: https://patentgrep.com/patent/US8542506B2

## CPC

- H02M 1/36: Means for starting or stopping converters
- H02H 3/08: responsive to excess current (responsive to abnormal temperature caused by excess current H02H5/04)
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)

## Abstract

A power isolation system and method is disclosed. The system includes a transformer suitable for use in the power isolation system, and a semiconductor device electrically connected to the transformer to provide a reduction of the inrush current associated with powering the transformer, wherein the semiconductor device is activated upon power up based upon the previous shutdown state of the power isolation system to provide a soft start to the transformer, and after activation of the transformer, the semiconductor device is shorted in the system.

## Claims

### Claim 1

A power isolation system, said system comprising:
a transformer suitable for use in the power isolation system;
a semiconductor device electrically connected to said transformer to provide a reduction of the inrush current associated with powering said transformer,
wherein said semiconductor device is activated upon power up of the power isolation system to provide a soft start to said transformer, and after activation of said transformer said semiconductor device is shorted in the system; and
a microcontroller for controlling the firing of the transformer to reduce the inrush current upon power up,
wherein said microcontroller monitors the phase angle of the incoming power signal and stores the phase angle at shutdown, and wherein the microcontroller makes a fire determination when the phase angle is approximately at the stored shutdown angle or if there is no stored shutdown angle at about 90 degrees.

### Claim 2 (depends on 1)

The system of claim 1, wherein said semiconductor device is a triac.

### Claim 3 (depends on 2)

The circuit of claim 2, wherein said triac comprises an alternistor.

### Claim 4 (depends on 1)

The system of claim 1, wherein shorting of the semiconductor device occurs by using a shorting relay.

### Claim 5 (depends on 1)

The system of claim 1, further comprising a protection for downstream devices.

### Claim 6 (depends on 5)

The system of claim 5, wherein said protection comprises a control relay that is opened for said protecting.

### Claim 7 (depends on 1)

The system of claim 1, wherein said microcontroller controls a shorting relay designed to short said semiconductor device from the circuit.

### Claim 8 (depends on 1)

. The system of claim 1, wherein said microcontroller controls a control relay designed to protect downstream devices during power up.

### Claim 9 (depends on 1)

The circuit of claim 1, wherein said transformer is a toroidal transformer.

### Claim 10 (depends on 1)

The circuit of claim 1, wherein said semiconductor device comprises a false trigger prevention circuit.

### Claim 11 (depends on 10)

The circuit of claim 10, wherein said false trigger prevention circuit includes at least one resistor.

### Claim 12 (depends on 10)

The circuit of claim 10, wherein said false trigger prevention circuit includes at least one capacitor.

### Claim 13 (depends on 10)

The circuit of claim 10, wherein said false trigger prevention circuit includes a RC circuit.

### Claim 14 (depends on 1)

The circuit of claim 1, wherein said semiconductor device comprises a snubber circuit for assisting in the turn off of said semiconductor device once said transformer is substantially fully powered.

### Claim 15 (depends on 14)

The circuit of claim 14, wherein said snubber circuit includes a RC circuit.

### Claim 16

A method of soft starting a transformer, said method comprising:
monitoring the phase angle of an incoming AC signal:
configuring a semiconductor device in a zero conduction configuration;
opening a relay to place the semiconductor device in the circuit containing the transformer;
increasing the conduction of the semiconductor device from zero to full conduction;
after full conduction is achieved on the semiconductor device, shorting the semiconductor device from the circuit containing the transformer;
controlling the firing of the transformer by a microcontroller to reduce the inrush current upon power up; and
said microcontroller monitoring the phase angle of the incoming power signal, storing the phase angle at shutdown, and making a fire determination when the phase angle approximately at the stored shutdown angle or if there is no stored shutdown angle at about 90 degrees.

### Claim 17 (depends on 16)

The method of claim 16, further comprising opening a control relay on the secondary side of the transformer to protect downstream devices.

### Claim 18 (depends on 17)

The method of claim 17, further comprising after full conduction is achieved on the semiconductor device, closing the control relay to complete the secondary side of the circuit containing the transformer.

### Claim 19 (depends on 16)

The method of claim 16, further comprising determining the fire condition of the transformer.

### Claim 20 (depends on 19)

The method of claim 19, wherein said step of determining the fire condition is performed by a microcontroller.

### Claim 21 (depends on 19)

The method of claim 19, wherein the fire condition occurs when the 90 degrees phase angle of the incoming AC signal occurs.

### Claim 22 (depends on 19)

The method of claim 19, wherein the fire condition occurs when the phase angle is equal to the last shutdown.

### Claim 23

A method of stopping conduction to minimize the residual flux of a transformer, said method comprising:
opening a relay to place a semiconductor device in the circuit containing the transformer;
ramping the conduction of the semiconductor device from full to substantially zero conduction,
after substantially zero conduction is reached on the semiconductor device, the residual flux of the transfer is minimized; and
a microcontroller for controlling the firing of the transformer to reduce the inrush current upon power up monitoring the phase angle of the incoming power signal and storing the phase angle at shutdown, and
the microcontroller making a fire determination when the phase angle is approximately at the stored shutdown angle or if there is no stored shutdown angle at about 90 degrees.

### Claim 24 (depends on 23)

The method of claim 23, wherein said ramping to substantially zero conduction comprises falling below the holding current of the semiconductor device.

### Claim 25 (depends on 23)

The method of claim 23, further comprising configuring the semiconductor device in a full conduction configuration.