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Frequently Asked Questions
- Which Soft Start should I choose for my motor?
- What sort of application should Soft Start not be used on?
- How many Starts can I do?
- What size Soft Start should I choose?
- Where should I use Current Limit and what level of current will I keep it down to?
- Do I need to use Soft Stop and what advantage is Linear deceleration/Tacho Feedback?
- Do I need Power Factor Correction?
- Do I need High Speed Fuses?
- What is the minimum allowable motor current when using a Softdrive 201 open loop soft starter?
- What is the minimum allowable motor current when using a Softdrive 202 closed loop soft starter?
- What type of motor protection does the Softdrive 202 have?
- What is the current consumption of the Softdrive 200 control supply?
- How can the Softdrive 202 programmable output relay be used?
- Is the Softdrive 202 suitable for flying start application?
- Why is it necessary to apply control voltage before (or with) mains voltage?
- What are the under- and over-frequency trip points for Softdrive 200 soft starters?
- Will the motor start DOL if the start ramp of Softdrive 201 open loop soft starter is set to "full voltage"?
- Do I need seperate CT's for Protection Circuits?
- Does overload remain in Circuit if I by-pass Softdrive 300?
- Relays on card not energising
- Excessive time before motor starts to turn
- Drive trips on 'time out' starts
- Trips at top of ramp
- Trips on overload
- Trips on fault 1
- Trips on fault 4
This would depend on the application in question the power and current of the motor:
- below 11k.w. Microstart
- 7.5k.w. - 110 k.w. Amp Ramp
- 7.5k.w. - 110 k.w. Softdrive 200
- 7.5k.w. - 800 k.w. Softdrive 300
Above 11kw there are 3 different types of soft start, the Softdrive 200, Amp Ramp and Softdrive 300.
The Amp Ramp is a simple soft start with ramp up and current limit along with initial torque adjustment.
The Softdrive 200 extends the feature by adding ramp down (soft stop), instantaneous over current and kick-start for high stiction loads.
The Softdrive 300 is a multi-functional digital soft start that includes all the features offered by Amp Ramp and Softdrive 200 with the addition of electronic overload and earth fault as point of a comprehensive motor protection package. The Softdrive 300 also includes communication facility or full LCD text display keypad control. These 4 product options offer the customer complete choice based on price and control features required.
It should not be used on applications requiring full torque at zero speed. The reduced voltage principle means reduced torque is achieved so full torque cannot be reached. Otherwise most AC motor applications are suitable for operation with Soft Start. Either constant or variable torque applications are suitable.
Standard is 12 Starts per hour. A Soft Stop is also classed as a Start function so if Soft Starting and Soft Stopping this would mean 6 Soft Starts and 6 Soft Stops per hour.
This depends on the application being looked at but in general the Soft Start can be sized Amp for Amp in that if the motor is 25 Amps a 25 Amp Soft Start can be chosen as this will allow for a starting current of 500% for 5 seconds or 300% for 30 seconds.
In certain cases it may be necessary to upgrade the Soft Start.
- High Number of Start/Stops
- High Altitude (above 2000M)
- High Ambient Temperature (above 40°C)
- High Starting Current or Time
This can be calculated if necessary by Softstart Direct being given relevant information but High Starting Currents can be expected on applications where there is a high inertia or starting torque (i.e. Fans, Mixers, Crushers, Grinders, Centrifuge, Hammer Mills and Mill Drives.)
Any application where you require a limitation may benefit from Soft Start but it has to be a practical Current Limit. The effect Current Limit has is a limitation to the motor starting torque therefore any limitation set too low may result in the motor not producing enough torque to accelerate the load. In practice Soft Start will limit starting current to a minimum required by the load to achieve acceleration. In practical terms this is usually:-
- Pumps 200-300%
- Compressors 250-350%
- Fans 300-500%
- Conveyors 200-400%
depending on torque requirement of load.
Soft Stop is only beneficial on applications requiring a slow deceleration of a motor; if a motor already coasts down slowly with its own inertia then it is probably not required (i.e. fans, compressors, mixers). Applications where it is most beneficial are where an Electrical Soft Stop (i.e. smooth deceleration) will produce mechanical benefits. Pumps and conveyors are examples of this, where a slow ramp down will provide a smooth stop.
Soft Start does not improve Power Factor therefore separate Power Factor would be required. Please ensure PFCs are energised once motor is up to full speed.
Soft Fuses are designed for thyristor protection under short circuit conditions.
Please click here for more details.
What are Switches SW1 + SW2?
SW1 is fitted on 15kW Amp Ramp. This selects motor power at either 7.5, 11 or 15 kW as instructed in the Amp Ramp manual.
SW2 is fitted to all Amp Ramps and this allows control of stop delay and restart delay. These functions are detailed in the Amp Ramp manual.
Why when I turn the power on does the Power On light not illuminate?
Unit is phase sensitive; Swap 2 phases around.
Softdrive 200 Series
There is no minimum current when using a Softdrive 201 open loop soft starter.
The minimum "Motor FLC" setting is 50% of the Softdrive 202 nameplate rating. All Motor protections are based on this setting.
It is possible to operate a Softdrive 202 with a small kW motor, for testing purposes. In this case, the motor will effectively start DOL, and the Softdrive 202 will not protect the motor. The starter will trip, because there is no under-current protection on Softdrive 202.
The Softdrive 202 has built-in motor overload protection of the electronic "thermal model" type. The motor current is continuously monitored and the expected temperature is calculated based on this monitored current.
The rate of rise of the calculated motor temperature is determined by the motor trip class setting. The lower this setting, the faster the rate of rise calculated motor temperature. An overcurrent trip (x2 ready LED flashes) will occur when the calculated temperature reaches 105%. The setting of the motor trip class pot is similar to a motor trip class setting on a standard thermal overload relay.
An external motor protection device is not required when using a Softdrive 202 soft starter. Softdrive 202 is certified to conform to the IEC60947-4-2 standard for electronic soft starters. The reliability of the motor protection feature is part of this standard.
The steady state consumption of the control supply is 100 mA maximum, however the short time inrush current at control supply "switch-on" can be as high as 10A.
The programmable output relay provides an N/O contact, which can be used for a "trip" or "Run" output.
The relay operates when the Softdrive 202 trips on any fault. This can be used to operate a shunt-trip mechanism of an upstream circuit breaker to isolate the motor branch circuit. It could also be used to signal Softstart 202 "Trip" status to an automation system.
The relay operates on completion of start ramp. This can be used to operate a contactor for power-factor correction capacitors. It could also be used to signal Softdrive 202 "Run" status to an automation system.
Is the Softdrive 202 suitable for flying start application?
Yes. There is a built-in 2 second delay between the end of one stop and the beginning of the next start. This delay allows the motor flux to decay, eliminating any chance of the Softdrive 202 tripping on Power Circuit fault (x1 flash) due to detection of motor back EMF when the start signal is applied. The major effect of a flying start is on the actual time the Softdrive 202 current limits. The ramp-up time will be reduced and is determined by the motor speed on re-application of the start signal.
There is a possibility the soft starter could arrive at site with the internal bypass relay in "closed" state. On first application of control voltage, the bypass relays are commanded to open. If mains voltage is applied without control voltage, this step is missed and the motor may start DOL without warning (refer Product Note for more detail).
The trip points are 40 & 72 Hz. If the frequency falls below 40 Hz or rises above 72 Hz, the soft starter will trip (x 6 ready LED flashes). These trip points are not adjustable.
A Supply frequency trip will also occur if all 3 phases from the mains supply are lost, or fall below approximately 120 V AC while the soft starter is running.
A supply frequency trip will occur if the line contactor drops out during running.
Will the motor start DOL if the start ramp of Softdrive 201 open loop soft starter is set to "full voltage"?
No, the Softdrive 201 will still provide a limited soft start. The voltage is ramped up from 0 to 100% in approximately 0.25 seconds.
Do I need seperate CT's for protection circuits??
The Softdrive 300 has in built CT's for current detection and protection. However, whilst the Softdrive 300 has anearth fault feature, CT's for this function are not included. A separate core balance CT is required on units up to 130kW and units above this size require 3 separate 4000:1 protection class CT's with saizca transorb suppressors fitted. Please advise Softstart Direct if earth fault is required so we can ensure CT's and burden resistors are matched.
With Softdrive 300 the terminals are arranged so connection of by-pass contactor is separate to motor connections meaning CTs are still in circuit during by-pass and hence as long as power is maintained to Keypad the overload is still in circuit. This is similarly the case for under and over current protection on the Softdrive 300.
Typical Setup Problems
Check correct control voltage on PCB.
Increase pedestal setting.
Current time limit at trips showing current is active for longer than 20 seconds: current limit setting too low or perhaps current limit time-out needs increasing.
Drive not set for by-pass mode in menu 2.
Drive needs overload setting up as manual describes.
Check U/V setting on Softdrive 300. Check mains fuses. Check to ensure some output on Softdrive 300.
Check phase rotation. Phase sensing can be disabled by switching autophase on.