GB2299224A

GB2299224A - Motor bearing and/or winding protection circuit

Info

Publication number: GB2299224A
Application number: GB9504974A
Authority: GB
Inventors: Jim Ormiston; Russell Green
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-03-11
Filing date: 1995-03-11
Publication date: 1996-09-25
Also published as: GB9504974D0

Abstract

The protection circuit has temperature sensors 1 located close to the bearings and windings which send a voltage signal of actual temperature to comparators 2,3,4,5,6,7 and 10 and sample and hold circuit 11. If the voltage signals exceed pre-set limits then the comparator outputs are enabled and signals are sent to trip unit 12 and warning indicators 14. The sample and hold circuit 11 is switched by a clock input 13 at pre-set timing intervals, and sends a voltage signal to the comparator 10. A desired temperature limit is added to this signal which is held for the duration of the hold cycle and continually compared to the voltage signal received from the sensor 1. If the temperature rises excessively during this period, the comparator output is enabled and a signal is sent to the trip unit 12.

Description

BEARING AND/OR MOTOR WINDING PROTECTION CIRCUIT.

This invention relates to a Bearing and/or Motor Winding Protection Circuit.

The majority of electric motors are presently protected by various known means,the most common of which being the over-load switch.

Over-load switches operate basically by means of a bimetallic strip incorporated into their construction whereby should the electric motor become over-loaded then the resulting increase in heat causes the bimetallic strip to elevate and connect with a trip unit tripping out the power supply to the electric motor.

Over-load switches are not very reliable and do not provide any advance warning to the user that the electric motor is beginning to over-load.

Also,over-load switches do not provide direct protection to the electric motor bearings or to windings as a result from heat from damaged bearings, and frequently damage has been caused to the bearings before the over-load operates and trips out the power supply to the electric motor.

In many other cases damage has also been caused to the electric motor windings before the over-load operates and trips out the power supply to the electric motor.

Another problem with over-load switches is that a different size of over-load switch is required for different sizes of electric motors.

There are also various monitoring devices available that can be used to inform the user of the performance status of the electric motor.

However,these devices tend to be very expensive.

Therefore,the main purpose of this invention is to provide a Bearing and/or Motor Winding Protection Circuit that can be used in any size of electric motor to protect the bearings and the windings of the electric motor against over-heating.

The Bearing and/or Motor Winding Protection Circuit can also be used to provide the user with warnings at any stage of a developing problem of over-heating in the bearings or the windings of the electric motor being protected.

The Bearing and/or Motor Protection Circuit can also be used to provide the electric motor windings with further protection against over-heating in instances when the electric motor has been jammed.

A specific embodiment of the invention will now be described by means of example with reference to the accompanying drawing in which:- Figure 1 shows a block diagram of the electrical circuit of the BEARINGS AND/OR MOTOR WINDING PROTECTION CIRCUIT comprising of at least one of each of the following items; a Temperature Sensor, a Comparitor,a Sample and Hold,a Clock Input,a Trip Unit and Electronic Signal Connections.

Optionally,the Bearing and/or Motor Protection Circuit may also included at least one Warning Indicator.

In the following example of the Bearing and/or Motor Winding Protection Circuit two optional warning levels have been incorporated into the Bearing and/or Motor Winding Protection Circuit.

If the temperature of the bearing/s increases through, for example,loss of lubricant,the bearing and/or motor winding protection circuit processes the information as described below.

If the temperature of the winding/s increases through, for example,an increase in the electrical current in the windings,the bearing and/or motor protection circuit processes the information as described below.

The Warning Indicator(s) may be any type of electronically operated audio,visual or combined alarm unit.

The Warning Indicator(s) may have optional advisory warning levels and there may be any number of these or none at all.

The Electronic Signal Connections may be of,for example,wire cable or other suitable means for conducting electronic signals.

The Trip Unit may be any type of switching device and connected to the electric motor power supply by means of, for example,wire cable or other suitable electrical conducting means,whereby,should the Trip Unit be energised then the power supply to the electric motor would be cut off.

In the following example all the Comparitors noted can be pre-set at desired limits and these limits can be altered when required.

The Comparitors may be of the type having at least two inputs and one output.

The Comparitors may have a reference limit pre-set into one input and this reference limit can be altered as required.

Each Comparitors included within the circuit may have a different pre-set reference limit.

The Clock Input Unit may be an Astable Timer type and have a preset timing rate which can be altered as required.

Refering to the drawing the BEARING AND/OR MOTOR WINDING PROTECTION CIRCUIT comprises of at least one of the following items; a Temperature Sensor 1 connected to Comparitor 2,Comparitor 3 and Comparitor 4 by means of Electronic Signal Connections 8; a Temperature Sensor 1 connected to Comparitor 5,Comparitor 6 and Comparitor 7 by means of Electronic Signal Connections 8; a Temperature Sensor 1 connected to Comparitor 9,Comparitor 10 and Sample and Hold 11 by means of Electronic Signal Connections 8; a Trip Unit 12 connected to Comparitor 4,Comparitor 7 and Comparitor 10 by means of Electronic Signal Connections 8; a Sample and Hold 11 connected to Clock Input Unit 13 and Comparitor 10 by means of Electronic Signal Connections 8; an optional Warning Indicator 14 connected to Comparitor 2 and Comparitor 5 by means of Electronic Signal Connections 8; an optional Warning Indicator 14 connected to Comparior 3 and Comparitor 6 by means of Electronic Signal Connections 8.

In order to operate the BEARING AND/OR MOTOR WINDING PROTECTION CIRCUIT as an electric motor protector then the BEARING AND/OR MOTOR PROTECTION PROTECTION CIRCUIT should be connected to a suitable power supply.

At least one Temperature Sensor 1 can be located close to each set of bearings of the electric motor to be protected.

Each Temperature Sensor 1 is used to monitor the temperature at each set of bearings of the electric motor.

Each Temperature Sensor 1 generates a voltage signal of actual temperature at present time and sends these voltage signals through Electronic Signal Connections 8 to Comparitor 4 and Comparitor 7.

Optionally, each Temperature Sensor 1 generates a voltage signal of actual temperature at present time and sends these voltage signals to Comparitor 2,Comparitor 3,Comparitor 5 and Comparitor 6.

If the voltage signal of actual temperature being received by Comparitor 4 from the Temperature Sensor 1 through Electronic Signal Connections 8 exceeds the pre-set limit of Comparitor 4 then the Comparitor 4 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Trip Unit 12 energising the Trip Unit 12 and tripping out the power supply to the electric motor.

If the voltage signal of actual temperature being received by Comparitor 7 from the Temperature Sensor 1 through Electronic Signal Connections 8 exceeds the pre-set limit of Comparitor 7 then the Comparitor 7 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Trip Unit 12 energising the Trip Unit 12 and tripping out the power supply to the electric motor.

If the voltage signal of actual temperature being received by Comparitor 2 from the Temperature Sensor 1 through Electronic Signal Connections 8 exceeds the pre-set limit of Comparitor 2 then the Comparitor 2 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Warning Indicator 14 energising the Warning Indicator 14.

If the voltage signal of actual temperature being received by Comparitor 3 from the Temperature Sensor 1 through Electronic Signal Connections 8 exceeds the pre-set limit of Comparitor 3 then the Comparitor 3 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Warning Indicator 14 energising the Warning Indicator 14.

If the voltage signal of actual temperature being received by Comparitor 5 from the Temperature Sensor 1 through Electronic Signal Connections 8 exceeds the pre-set limit of Comparitor 5 then the Comparitor 5 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Warning Indicator 14 energising the Warning Indicator 14.

If the voltage signal of actual temperature being received by Comparitor 6 from the Temperature Sensor 1 through Electronic Signal Connections 8 exceeds the pre-set limit of Comparitor 6 then the Comparitor 6 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Warning Indicator 14 energising the Warning Indicator 14.

At least one Temperature Sensor 1 can be located close to each set of windings of the electric motor to be protected.

Each Temperature Sensor 1 generates a voltage signal of actual temperature at present time and sends this voltage signal simultaneously through Electronic Signal Connections 8 to Comparitor Maximum Comp 10 and Sample and Hold 11.

If the voltage signal of temperature received by Comparitor Maximum Comp 10 exceeds the pre-set limit of the Comparitor Maximum Comp 10 then the Comparitor Maximum Comp 10 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Trip Unit 12 energising the Trip Unit 12 tripping out the power supply to the electric motor.

The Sample and Hold 11 circuit is switched by an Astable Timer Input Unit 13 at pre-set timing rates,for example,Sample ten milli seconds;Hold two seconds.

The Astable Timer Input Unit 13 signal which may be from a timer, relay or other suitaable means of activating the Sample and Hold circuit.

The signal from the Sample and Hold 11 is sent through Electronic Signal Connections 8 to the Comparitor 10 input (A),added to this signal is the desired temperature limit (for example,one degree centigrade.This limit can be reset).

This signal is held at this present level for the duration of the Sample and Hold 11 hold mode timing period (for example,two seconds.This timing period can be reset).

If during this period the voltage signal received from the Temperature Sensor 1 to the Comparitor 10 input (B) rises above the voltage signal to the Comparitor 10 input (A) then the Comparitor 10 output is enabled generating a voltage signal which is sent through Electronic Signal Connections 8 to the Trip Unit 12 energising the Trip Unit 12 tripping out the power supply to the electric motor.

The Sample and Hold 11,Astable Timer Input Unit 13,Comparitor 10 and Temperature Sensor 1 circuit monitor the rate of temperature rise.(Temperature to time).

The circuit compares the rate of rise of temperature to known (set/reset) limits or values.For example,limit set to one degree centigrade and two seconds.

Therefore,a rise of,for example,zero point nine degrees centigrade within two seconds is acceptable,but a rise of one point one degrees centigrade within two seconds is not acceptable and would enable the Comparitor 10 output.

Claims

CLAIM8 The following Claims refer to a Bearing and/or Motor Winding Protection Circuit as substantially described in Patent Application GB 9504974.8 with reference to the accompanying drawing Figure 1.

1 A bearing and/or motor winding protection circuit comprising an electronic circuit containing at least one of each of the following components; a temperature sensor,a comparitor,a sample and hold, a clock input unit,a trip unit and electronic signal connections.

2 A bearing and/or motor winding protection circuit as claimed in Claim 1 whereby the described electonic circuit can also include at least one warning indicator.

3 A bearing and/or motor winding protection circuit as claimed in Claim 1 or Claim 2 that is universal in fitting to any size of motor.

4 A bearing and/or motor winding protection circuit as claimed in Claim 3 whereby the comparitor,sample and hold,clock input unit and warning indicator levels are all user settable to desired limits.

5 A bearing and/or motor winding protection circuit as claimed in any preceeding Claim that will protect a motor against the effects of overcurrent in windings and/or the effects of degradation in bearing condition by switching off electrical supply to the motor should set limits be exceeded.

6 A bearing and/or motor winding protection circuit as claimed in Claim 5 from which advisory warning level(s) signals may be obtained warning of changes in motor performance.

7 A bearing and/or motor winding protection circuit as claimed in any preceeding Claim that digital and/or analogue signals may be obtained by suitable electronic connections and these signals will interface by suitable electronic connections with external monitoring/control devices.

8 A bearing and/or motor winding protection circuit substantially as described herein with reference to Figure I of the accompanying drawing.