Load indicator

• US 6,879,260 B1
• Filed: 04/27/2000
• Issued: 04/12/2005
• Est. Priority Date: 10/28/1997
• Status: Expired due to Fees

• Current Assignee: Emotron AB (Tube Investments of India Ltd.)
• Original Assignee: Emotron AB (Tube Investments of India Ltd.)
• Inventors: Ranger, Martin, Zellman, Per, Olofsson, Lars-Olof
• Primary Examiner(s): Mullen, Jr., Thomas J.
• Assistant Examiner(s): TANG, SON M
• Application Number:
  US09/559,146
• Time in Patent Office: 1,811 Days
• Field of Search: 340/648, 340/676, 340/686.3, 340/607, 340/608, 340/611, 340/679, 340/511, 340636-664, 318/430, 318/431, 318/432, 318/433, 318/434, 318/783
• US Class Current: 340/648
• CPC Class Codes: G01R 21/133 by using digital technique
• CPC Class Codes: H02H 3/04 with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned watching of pilot wires H02H1/0084; protection of protective arrangements H02H7/008; indication of the state of electronic switches H03K17/18
• CPC Class Codes: H02H 7/085 against excessive load H02H6/00 takes precedence

Abstract

A load indicator for an electric motor, comprising a first means (II, IU, CPU) for repeated determination of the motor load, a second means (CPU) for comparing the current motor load, as determined by the first means, with a preset load limit, and a third means (CPU), PP) for indicating that the current motor load exceeds the load limit. Moreover, a meant (T, CPU) is arranged to initiate a presetting of the load limit. This means is adapted to be actuated, when the motor runs in normal operation, for presetting of the load limit as the current motor load changed by a predetermined deviation value stored in the load indicator.

Claims

1. A load indicator for an electric motor, comprising a first means (II, IU, CPU) for repeated determination of the motor load, a second means (CPU) for comparing the current motor load, as determined by the first means, with a preset load limit, a third means (CPU, PP) for indicating that the current motor load exceeds the load limit, and a means (T, CPU) for initiating a presetting of the load limit as the current motor load changed by a predetermined deviation value stored in the load indicator, said initiating means being adapted to be manually actuated as the motor runs in normal operation.

2. A load indicator as claimed in claim 1, wherein the deviation value is stored as a percentage which, multiplied by the nominal power of the motor, yields the actual deviation value.

3. A load indicator as claimed in claim 1, wherein the deviation value is stored as a percentage which, multiplied by the current load, yields the actual deviation value.

4. A load indicator as claimed in claim 1, wherein deviation value is stored as a fixed value.

5. A load indicator as claimed in claim 1, wherein the initiating means (T, CPU) is adapted to preset two deviation values which represent deviations in the same direction of either underload or overload with respect to the motor load in normal operation.

6. A load indicator as claimed in claim 5, further comprising a means (1) for determining the direction of deviation.

7. A load indicator as claimed in claim 1, wherein the initiating means (T, CPU) is adapted to preset two deviation values which represent deviations in opposite directions of underload and overload, respectively, with respect to the motor load in normal operation.

8. A load indicator as claimed in claim 1, wherein the initiating means (T, CPU) is adapted to preset four deviation values, of which two represent different deviations in a first direction from the motor load in normal operation and two represent different deviations in a second direction, opposite to the first direction, from the motor load in normal operation, said first and second directions being either an underload or overload direction, respectively with respect to the motor load in normal operation.

9. A load indicator as claimed in claim 1, wherein the first means (II, IU, CPU) is adapted to determine the current motor load as the supplied power reduced by a value that represents the lost power of the motor.

10. A load indicator as claimed in claim 1, wherein the first means (II, IU, CPU) is adapted to determine the current motor load as the supplied power.

11. A load indicator as claimed in claim 1, wherein said initiating means includes a key arranged to start the presetting of the load limit when pressed.