What is OP1S?

In the modern world industrial sector as the technology getting smarter, the way of representation and manipulation of them also are getting smarter.

OP1S is that kind of optional device that makes the Drive handling operation much easier by working as the substitute secondary display device. But the main function is that it works not only as a display device but also it got some features of accessing drive parameter and modifying them much easily.

OP1S

Also another interesting feature of OP1S is that it has non volatile memory on which it can easily upload parameters from drives. It can store couple of sets of complete parameter set of different drives. And it’s also easy to download parameter sets into drives. And this upload and download function requires no additional equipment. It’s very helpful in case of emergency.

The communication of OP1S is done via a RS485 serial interface using the USS protocol and one OP1S unit is capable of communicating up to 32 slaves with baud rate of 9.6 kBd and 19.2 kBd.

OP1S has a multi language plain text display which also configurable form drive parameter. OP1S also got a numeric keypad with which you can jump over parameter where in case of PMU going from one parameter to another distant parameter is very much boring and time consuming.

OP1S Connected with Drive

Another advantage of OP1S is that OP1S unit is broadly used in different variety of drives which makes it a common device and can be shared with others. Its plug in connection also makes it too popular. When it is connected with cabinet door with adapter plug in when you need and plug off when you need it in another place.

SIMOREG 6RA70 DC MASTER

SIMOREG 6RA70 DC MASTER is one of the best DC DRIVE series made by SIEMENS. It leads the industrial sector from its very begging of the journey. Also still leading, though a couple of new model drives with some extra feature are released in last couple of years but it holds its position.

SIMOREG 6RA70 DC MASTER is available in different voltage range; they are 400V, 460V, 575V, 690V, and 830V. Also the range can be enlarged by parallel and series operation of them. And it was also the most exciting feature of SIMOREG 6RA70 DC MASTER.

SIMOREG 6RA70 DC MASTER series Drives

Common Features
Some of the most common feature that makes 6RA70 series most popular are as follow:

1. Its user friendly interface.

2. Wide variety of power Range.

3. 6RA70 series make the parallel connection theme so easy.

4. Power consumption of its own is very low, that makes its performance extra ordinary.

5. Anyone with little knowledge can make the commissioning of the 6RA70 but it’s not recommended but it is helpful in case of emergency as every with knowledge can handle it.

6. Can be expanded in a unified modular fashion with MASTERDRIVES standard options

7. The mechanical design it also very compact hence takes smallest area possible.

8. It is also compatible with previous SIMOREG Range.

Basic Electronic Feature

 6RA70 DC MASTER can operate on both open loop and Close loop operation.
 Introduce more flexibility in operation and modification with BICO Technology.
 Drives can optimize automaticaly and make the complex tunning which lead in its smooth operation.
 Easy and structured diagonstic system makes finding faults more quickly also quick hint helps in solving the problem.
 Also can be expanded with freely configurable block.
 User friendly operator panel OP1S.
 No jumper is needed on Parameterization.
 Technology software included in basic unit
 Flash - EPROM
 user-friendly evaluation of alarms / faults
 all parameters can be set-up and monitored
 all parameter sets can be upread / downloaded

Parametrization unit of SIMOREG 6RA70 DC MAster

Communication Feature

 Using USS protocol communication is done with PC and external control connection.
 Communication through PROFIBUS-DP
 Direct drive-to-drive coupling (SIMOLINK) communication option also provided.
 Peer-to-peer connection
 1 x RS232 (or RS485) for OP1 S or SIMOVIS

Different Slots in 6RA70 DC MASTER

6RA70 Drives has different types of slots to accommodate different functionality devices. They are as follow:

 Encoder (Sensor Boards)
- SBP Pulse Encoder (TTL/HTL)
 Fieldbus (Communication Boards)
- CBP PROFIBUS DP (12 Mbaud)
 Technological link
- SLB SIMOLINK
 I/O-boards (Expansion Board)
- EBx

Operation Range for the whole world is as follow:

NEMA / CSA 3-ph. 460 V AC 60 Hz 3-ph. 575 V AC 60 Hz	IEC 3-ph. 380 - 415 V AC 50 Hz 3-ph. 500 V AC 50 Hz 3-ph. 660 - 690 V AC 50 Hz
IEC / NEMA 3-ph. 380 - 460 V AC 50/60 Hz	IEC / NEMA 3-ph. 380 - 460 V AC 50/60 Hz
IEC 3-ph. 380 - 440 V AC 50/60 Hz 3-ph. 500 - 550 V AC 50/60 Hz

Carbon Brush

About Carbon Brushes:
1. Carbon Brush	2. Why Carbon is Selected as the medium?
3. Current Density in Carbon Brush	4. Why Carbon Brushes are split?
5. What is Patina?

For many years inventors were trying transmit current form a stationary body to a rotating body. It was the main obstacle in rotating machinery. Finally they found out a way. Initially it was done by bundling copper wires and fixed then with stationary body and keep contact with the rotating body. In this way the copper bundles looked like paint brush. And the word brush came from there. 

With the development of knowledge and technology and after years of experiment finally a well structured process invented. Now in almost all modern technology different grades of carbon blocks are used as the transmitting medium. Though they don't look like brush but as a tradition they are well known as carbon brush.

With the help of brush holder and spring the remain touched with the rotating body and transmit current.

Why Carbon is Selected as the medium?

About Carbon Brushes:
1. Carbon Brush	2. Why Carbon is Selected as the medium?
3. Current Density in Carbon Brush	4. Why Carbon Brushes are split?
5. What is Patina?

In all modern technology for transmitting current from a stationary body to a rotating body carbon brush is used. The main reasons for using carbon are as follow:

a) First of all is its conductivity which is as like as metal.

b) The main disadvantage metal is that in some temperature metal melts. Most often metal welded because of this property. On the other hand carbon does not melt. It does not hold any liquid state. It vaporize directly from solid state. It is another very good advantage of using carbon brush. No probability to be welded with commutator or slipring. Also its evaporation  temperature is also too high. It is almost 3000 to 4000 degree Celsius.

c) Carbon is lighter than many metal which also make it's inertia much low and because of this low inertia carbon brush can move easily and smoothly over little rough surface without causing any trouble. 

d) Another important quality is carbon is self lubricating which means low friction. As temperature rises unlike any other metal carbon friction coefficient decreases making it suitable for using in rotating machinary.

e) Chemically carbon is stable and it's expansion is also negligible.

These are some reasons which make carbon as a best choice.

Why Carbon Brushes are split?

About Carbon Brushes:
1. Carbon Brush	2. Why Carbon is Selected as the medium?
3. Current Density in Carbon Brush	4. Why Carbon Brushes are split?
5. What is Patina?

Generally carbon brushes not used as single blocks. Normally two wafers are bonded with a cushion pad. Three wafers also seen in the industrial sector. Brush sizes and design and grades depends on many criteria and normally is matter of experts.

The splitting is mainly done to increase the contact points. Theories says that the number of contact point does not depend on brush cross sectional area. It is kind of fixed. Normally a carbon block has around 10 contact point regardless with its contact area. So Splitting carbon brushes increase the contact point. If we use two wafer carbon brush then there will almost 20 contact point available.

And also the increased cross resistance due to splitting helps in commutation which is the another good side of brush splitting.

What is Patina?

About Carbon Brushes:
1. Carbon Brush	2. Why Carbon is Selected as the medium?
3. Current Density in Carbon Brush	4. Why Carbon Brushes are split?
5. What is Patina?

Patina is also know as film or skin over DC motor commutator. It is mainly copper oxide that formed on a commutator surface as a result of reaction among copper, graphite, oxygen and other free particles in some range of temperature. Patina is a very thin film and can easily damaged.

Patina is very helpful in commutation, it makes commutation smooth. So during maintenance extra care should be taken to preserve patina.

Patina color

Normally in good condition patina formed all over the commutator evenly. And the color of patina can be slightly shinny, coppery brown to black. But keep in mind that the color of patina is not that important thing, the important thing is whether they are forming evenly or not.

Bad patina indicates some abnormality of the environment or the motor. Such as high humidity, presence of oil and grease particles, uneven commutator surface, uneven current distribution, low load operation, commutation problem, high resistance problem, raised mica, vibration etc.

Current Density in Carbon Brush

About Carbon Brushes:
1. Carbon Brush	2. Why Carbon is Selected as the medium?
3. Current Density in Carbon Brush	4. Why Carbon Brushes are split?
5. What is Patina?

Current density is normally expressed as amps per square cm or amps per square inch. Current density is simply the value of current that is passing through per unit area of carbon brush.

There are some points that effects the current density of carbon brush such as temperature, vibration, nature of operation continuous or intermittent, speed etc.

Current density in a carbon brush using in DC motor can be calculated with the following equation:

Current Density Equation

In Brush circuit contact area from Total number of brushes half brushes are used to carry in the current and half brushes are used to carry out the current.

For bottom angled brush the contact area is not just width X thickness but the contact area should taken into account. 

A carbon brush should not be operate in low current density. Low density operation is more dangerous than over density operation.

Finding fault histroy in Simoreg 6RA70 DC Drive

In SIMOREG 6RA70 DC drive there are built in options in the drive to generate various types of fault and store them in drive memory. 

For Diagnostic purpose when a fault occurred we need to see three things from drive. One is fault code or message. It give a overall idea about the fault. The second thing is the fault value. If we observe the drive manual under a certain fault there are some sub options identified by numbers. They are fault value. A fault value help up to be more specific about the fault. And as a maintenance engineer we should always keep an eye on how long the problem takes. The third thing is the occurrence time means when the problem occurred.

All these can be observed in a 6RA70 DC drive. Let see how. 

When a fault occurred it is probable that multiple problems can be occurred at a same time. In 6RA70 at best eight (8) these types of fault can be saved. Means it at the same time numbers of fault occurred then it can save up to eight (8) fault. 

Total eight(8) nos of fault history can be saved in it. Means eight faults from different time slot can be saved and in each time eight fault that occurred at the same time can be saved. When new fault occurred then the last one deleted.

The Fault code or fault value can be seen from the parameter p947 (r947) a read only parameter shows the fault code or message. In this parameter you see total of 64 index. First eight index is allotted for the first at a time occurred fault. Suppose only one fault occurred at a time then index 1 will be filled and other 7 index will be 0. 

The Fault value can be seen from r949 parameter. It is also a read only parameter. It holds the corresponding value for p947 ( r947) index. It has same nos of index like r947. 

And the Fault time can be seen from r049. It just got 8 index. 

Fault code, value and time

In index one current fault is stored if it is not acknowledged. Acknowledged fault moves to the below. From figure you see only 1,9,17,25,33,41,49,57 index are relevant .

It is a great feature of Simoreg 6RA70 drive. Proper using of fault code along with fault value save lots of time. It is a really helpful tool in industrial sector.

F030 fault in DC drive Simoreg 6RA70:dc master

Problem:

During running condition DC motor tripped showing “F030” fault.

Description:

I work in a Steel mill. And it is one of the renowned Steel mills in my country. Previously it was 18 stand mills but after some correction it is now 20 stand mill and for this purpose we changed one of DC motor named shear#2 or flying shear. We replaced it with 250KW DC motor. Previously it was 170KW. After changing this we faced with this new problem. It some times tripped in running condition especially in 3X12mm rolling showing F030 fault. We used DC drives from siemens and the model was Simoreg 6RA70.

The fault code was 2.

Analysis:

From simoreg DC master 6RA70 manual we see  F30 means the followings

From fault code we see the root cause of this fault trigger is “The current crest curve breaks upwards” as our fault code is 2 (two).

Now the interesting part, from this we understand that this problem must related to some monitoring function. As Shear#2 does not run all the time and only used for cobble chopping and optimization chopping, it is probable that it may take some extra current for very short time.

Then we found the particular monitoring parameter. It is U580 (2580) “Control word for commutation monitoring”.

By this parameter we define which commutation monitoring criteria the drive will use. In our drive it was select in 4. So Decision criterion 3 that means maximum current actual value is evaluated. That’s the reason as it was reaching the limit as it tripped.

Then we changed the parameter from 4 to 7 means all three criterion will be used.

Then the problem solved.

Regarding the manual and figure: 2

Each decision criterion has a numeric code.

If more than one decision criterion is to be evaluated, the sum of the relevant digits must be entered.

There also rules for selecting the parameter. If u select 0 then “none of the three criteria are evaluated” will be selected. If u select 1 then “Decision criterion 1 (sufficient voltage time area for commutation) is evaluated” will be selected. If u select 2 then “Decision criterion 2 (curvature of the current crest curve) is evaluated” will be selected. If u select 4 then “Decision criterion 3 (maximum current actual value) is evaluated” will be selected.

Now if you want to select both criterions 1 & 2 then enter value 3. If you want to select both criterions 2 & 4 then select 6. If you want to select all of the criterions then select 7, the sum of all codes.

Speed Regulation in DC Drives

We know,

From this equation we can say that with constant field flux and load on the motor, any change in incoming supply voltage will change the voltage delivered to the armature of the motor. 

Now if the incoming voltage supply and the field flux are steady but load on the motor fluctuates then, this will alter the current taken by the armature. 

Change in the load changes the current taken by armature which in turn changes the Eb level.

Since N α Eb, Changes in load causes speed to deviate from the set or required value. 

If we want the speed to remain steady at the set value even with fluctuations in incoming supply voltage or load on the motor or with both, then we shall need and electronically controlled variable speed D.C. drive with actual speed and current feedback

Figure : Simple Block Diagram

Provision to vary the speed of motor with soft start/stop circuit called Ramp Function Generator.

A Speed control loop for correcting the speed and hence regulating it called speed controller.

A current control loop for correcting the speed and hence regulating it called current controller.

  

Circuit to provide gate pulses to trigger SCRs in power converter called gate control set.

Ramp Function Generator:

Whenever we give the facility of speed variation we should control the rate of change of the speed i.e. we must control acceleration and deceleration for the safe operation.

It is achieved by a circuit which is called as Ramp Function Generator (RFG).

The Output of the RFG is the control input to speed controller

 Figure : Controlled Acceleration and Deacceleration

Following are the reasons for possible deviation of the speed from the set value.

1.  Supply Voltage Variation.

2.  Variation in load on the motor.

To achieve an ideal speed torque characteristics, it is essential to incorporate a speed  feedback for speed correction and regulation. 

The circuit consist of a simple PI controller which has two inputs

1. Set Speed value.

2. Actual Speed value.

Direction Reversal of D. C. Motor

As we know the torque developed M≈ IaΦ.

—

—

—Thus to develop torque in reverse direction either Armature current should be reversed.

—

—Or Φ should be reversed.

—

—To reverse Φ means Field Current should be reversed. 

Figure : Armature Reversal

Figure : Field Reversal

  

—In both the conditions because of inductive nature of the windings current and thus torque would not reverse at the instant of voltage reversal. 

◦ Figure : Time Delay

Field winding being more inductive than Armature would take larger time to provide reversal, thus Armature reversal is preferred.

Limitations of reversals

1. —It is clear that even if the voltage polarity of armature is reversed the current and hence torque direction does not change instantaneously. 
2. During this overlap when the torque and hence Eb is opposite to theapplied voltage, there will be practically ∞ current (limited only byarmature resistance) flowing in the armature circuit. 
3. So it becomes essential that before we reverse the polarity of armaturevoltage the earlier torque should cease and Eb should come to zerolevel.
4. Now the first step to achieve this is to make armature voltage zero.  
5. But this will not help because of the fact that motor will continue its rotation because of its inertia and keep generating Eb. 
6. Also the Ia will take its own time depending upon armature circuit timeconstant to come to its zero value after the removal of armaturevoltage.
7. This will take some time and thus instantaneous reversal is not be possible. 
8. To over come this we require the method wherein we forcibly make the Ia / T and Eb zero and proceed with reversing. 
9. This phenomenon is called as 'Braking'. 
10. The normal sequence of operation for reversal, therefore, would be Motoring followed by braking followed by reverse motoring.

Cooling System in DC Motor

There are several types of cooling system for DC Motor. One need to choose cooling system carefully. Some are described below.

Dripproof Fully Guarded Self Ventilated (DPFG):

The DPFGmotor is self ventilated, with no external cooling. Open dripproof motorsare modifiable to separately vented enclosures.They are suitable to deliver 100% rated torque down to 60% of base speed.

Dripproof Fully Guarded Blower Ventilated (DPBV):

This type ofenclosure has a blower, with or without filter, as a standard option. Theblower is mounted on the commutator end of the motor toprovide constant air flow CFM (ft.1/min.) for cooling. DC motors with blowerventilation deliver 100% of rated torque downto 5% of the motor’s base speed.

Dripproof Separately Ventilated (DPPV or DPSV) :

The dripproof, separatelyventilated DC motor uses ducted in air, which must provide the proper CFM inorder to cool the motor. This type ofmachine is capable of delivering 100% of rated torque down to 5% of its basespeed.

Totally Enclosed Separately Ventilated(TEPV or TESV):

The totally enclosed separately ventilated motor has airflow ducted in and ducted out. This air flow must provide the proper CFM to cool the motor. It is capable ofdelivering 100% of its rated torque down to 5% of base speed.

TotallyEnclosed Non-Ventilated (TENV):

The TENV machine hasno external cooling, but uses an internal fan to move air within the motor.These enclosures are designed to deliver100% of rated torque down to 5% of its base speed.

TotallyEnclosed Air Over (TEAO):

The totally enclosedair over motor has a blower mounted piggyback on top of the motor frame. Thisallows for constant air flow on the motorframe’s external surface. DC motors in totally enclosed air over enclosuresdeliver 100% rated torque down to 10% of base speed.

Totally Enclosed Fan Cooled (TEFC):

The TEFC machine hasan external fan mounted on the commutator end shaft. Air flow varies with the speed of the motor and is therefore notsuited for low RPM applications.

Totally Enclosed Unit Cooled (TEUC) Air-to-Air Heat Exchanger:

These units consistof an air-to-air heat exchanger that is cooled by an external air blowerassembly. The external air blower assembly draws airthough the air inlet. An internal air blower assembly circulates the internalcooled air through the motor.

DC Motor Basic

What is an Electric Motor? 

• Electromechanical device that converts electrical energy to mechanical energy 

• Mechanical energy used to e.g.
• Rotate pump impeller, fan, blower 
• Drive compressors 
• Lift materials.
• Motors in industry: 70% of electrical load 

Basic Electric Motor Parts:

Fleming’s Left Hand Rule  Or Motor Rule:

Fleming’s Right Hand Rule Or Generator Rule:

Type ofElectric Motors:

DCMotors – Components 

The DC motor consistsof the following components:

1) Motor frame(stator) tubular or laminated steel construction

2) End bells(brackets)

3) Armature: - Commutator Lamination  Shaft and bearings

4) Field coil andpole assemblies

5) Interpole coil and poleassemblies

6) Brush rigging: -Brushes, Brush holders and springs Rocker ring

Advantages of DCmotor:

– Ease of control

– Deliver highstarting torque

– Near-linearperformance

Disadvantages:

– High maintenance

– Large and expensive(compared to induction motor)

– Not suitable forhigh-speed operation due to commutator and brushes

– Not suitable inexplosive or very clean environment

You may see also

About Carbon Brush
Finding Fault History in DC drive 6RA70
F030 fault in DC drive 6RA70:dc master

Speed Regulation in DC Drives

Direction Reversal of D. C. Motor

Cooling System in DC Motor

DC Motor Basic