Electric heater for heating synthetic materials and method for operating the electric heater

Patent metadata

Field	Value
Publication number	US-9642188-B2
Application number	US-201514922454-A
Country	US
Kind code	B2
Filing date	Oct 26, 2015
Priority date	Oct 27, 2014
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

An electric heater ( 4 ) of a synthetic-material molding system ( 2 ) defines a current path ( 6 ) that includes a first measuring pickup ( 20 ), a second measuring pickup ( 22 ), a switch ( 16 ) and a third measuring pickup ( 24 ), all connected in series, wherein a heating element ( 14 ) is connected between the first measuring pickup ( 20 ) and the second measuring pickup ( 22 ). The electric heater ( 4 ) also has a diagnostic path ( 28 ) that includes a first diagnostic pickup ( 30 ), a first voltage measuring device ( 52 ), a second diagnostic pickup ( 32 ), a second voltage measuring device ( 54 ) and a third diagnostic pickup ( 34 ), all connected in series. The first measuring pickup ( 20 ) is electrically connected to the first diagnostic pickup ( 30 ) by a first protective impedance ( 38 ), the second measuring pickup ( 22 ) is electrically connected to the second diagnostic pickup ( 32 ) by a second protective impedance ( 40 ), and the third measuring pickup ( 24 ) is electrically connected to the third diagnostic pickup ( 34 ) by a third protective impedance ( 42 ).

First claim

What is claimed is:

1. An electric heater, comprising:
a current path comprising a first measuring pickup, a second measuring pickup, a switch, and a third measuring pickup, all connected in electrical series to define the current path with a heating element connected between the first measuring pickup and the second measuring pickup;
a diagnostic path comprising a first diagnostic voltage pickup, a first voltage measuring device, a second diagnostic voltage pickup, a second voltage measuring device, and a third diagnostic voltage pickup, all connected in electrical series;
a first protective impedance electrically connecting the first measuring pickup to the first diagnostic voltage pickup;
a second protective impedance electrically connecting the second measuring pickup to the second diagnostic voltage pickup; and
a third protective impedance electrically connecting the third measuring pickup to the third diagnostic voltage pickup.

2. An electric heater in accordance with claim 1 , wherein a resistance value of each of the first, second and third protective impedances is the same.

3. An electric heater in accordance with claim 1 , wherein at least one of the first protective impedance, the second protective impedance and the third protective impedance is connected to a reference potential by an additional impedance.

4. An electric heater in accordance with claim 3 , wherein the reference potential is ground.

5. An electric heater in accordance with claim 1 , wherein the switch comprises a TRIAC.

6. An electric heater in accordance with claim 1 , further comprising a control circuit, and wherein each of the first and second voltage measuring devices comprises a comparator connected to the control circuit.

7. An electric heater in accordance with claim 1 , further comprising first, second and third A/D converters, wherein the first A/D converter is connected between the first protective impedance and the first diagnostic voltage pickup, the second A/D converter is connected between the second protective impedance and the second diagnostic voltage pickup, and the third A/D converter is connected between the third protective impedance and the third diagnostic voltage pickup, and wherein the first and second voltage measuring devices are incorporated in a shared computing unit.

8. An electric heater in accordance with claim 1 , further comprising a fourth protective impedance, wherein the diagnostic path further comprises a fourth diagnostic voltage pickup and a fourth voltage measuring device, wherein the current path further comprises a fourth measuring pickup and a first fuse connected between the fourth measuring pickup and the third measuring pickup, wherein the fourth protective impedance electrically connects the fourth measuring pickup to the fourth diagnostic voltage pickup, and wherein the third voltage measuring device is electrically connected between the fourth diagnostic voltage pickup and the third diagnostic voltage pickup.

9. An electric heater in accordance with claim 1 , wherein the current path further comprises a second fuse, and wherein the first measuring pickup is connected between the second fuse and one of the heating element and the second measuring pickup.

10. An electric heater in accordance with claim 1 , wherein the switch is connected between the second measuring pickup and the third measuring pickup.

11. A method for operating the electric heater of claim 1 , comprising the steps of:
generating a first measurement value from the first voltage measuring device;
generating a second measurement value from the second voltage measuring device; and
comparing the first and second measurement values with stored values in a table of stored values.

Assignees

• Siemens Ag

Inventors

• Bach Christine
• Haase Axel
• Schneider Reinhard
• Stoll Jürgen
• Zinn Philipp

Classifications

• G01R19/10

  Measuring sum, difference or ratio · CPC title

• H05B1/023 Primary

  Industrial applications · CPC title

• H05B3/00 Primary

  Ohmic-resistance heating · CPC title