National Resistors

We National Resistors manufacture Resistance Boxes used for heavy duty requirement of starting and for speed control of electrical motors.

Motor Starting Resistors are used to reduce the voltage at the motor terminals and also decrease the starting current. Motor Starting Resistors are necessary because the self resistance of a motor armature is very low. With this gradually increasing torque and voltage, the acceleration becomes smooth.

This resistor allows a stepped starting  having high starting torque with low and limited starting currents. Suggested for high power motors and to drive equipments with strong inertia  and needs of fast accelerations and heavy, long and frequent startings

This resistor is used for gradual starting with the possibility to choose the torque in relation with the device to start. Suggested for equipments with low starting torque and increasing advancement.

Details Required from customer to provide quotation: 

• Motor Power (KW)
• Rotor Voltage (V)
• Rotor Current (A)
• % slip (10 or 15% slip is standard)
• Starting Torques
• No. of Steps

We National Resistors manufacture Resistance Boxes used for heavy duty requirement of starting and for speed control of electrical motors.

Motor Starting Resistors are used to reduce the voltage at the motor terminals and also decrease the starting current. Motor Starting Resistors are necessary because the self resistance of a motor armature is very low. With this gradually increasing torque and voltage, the acceleration becomes smooth.

This resistor allows a stepped starting  having high starting torque with low and limited starting currents. Suggested for high power motors and to drive equipments with strong inertia  and needs of fast accelerations and heavy, long and frequent startings

This resistor is used for gradual starting with the possibility to choose the torque in relation with the device to start. Suggested for equipments with low starting torque and increasing advancement.

Details Required from customer to provide quotation: 

• Motor Power (KW)
• Rotor Voltage (V)
• Rotor Current (A)
• % slip (10 or 15% slip is standard)
• Starting Torques
• No. of Steps

Slip/Buffer resistors are required when excessive loads are to be expected during operation, for example in a crusher drive. Slip resistors limit the torque in rotor circuits in slip ring motors when the motor is starting or is in operation. Torque limiting is normal during continuous operation. Should an overload occur, the slip resistor reduces the nominal speed and limits the motor torque. In normal operation the actual nominal speed remains constant.We manufactuire Buffer resistors from SS 304. These are non corrosive and stable resistors. The slip/buffer resistors are available in various ratings from 1-5 minutes or it can be intermittent or continuous. The Slip resistors are available with a slip of 10 or 15% as standard. The degree of protection of enclosure is as per customer’s requirement.

Major applications are Crusher Drive, Cutter drive, Chopper drive,etc…OR where the flywheel effect on motor.It’s used in series with rotor circuit. It can be continuous or can be bypass/inserted in circuit via contactor when required.

Details Required from customer to provide quotation:

• Motor Power (KW)
• Rotor Voltage (V)
• Rotor Current (A)
• % slip (10 or 15% slip is standard)
• Starting Torques