ABB SPAM150C Motor Protection Relay

Brief Introduction

The SPAM150C Motor Protection Relay is a general purpose combination relay designed primarily for the protection of AC motors for a variety of applications.

It combines a large number of protection functions in one unit. The relay provides a complete set of protection against motor damage caused by various electrical faults.

The relay is also suitable for other equipment requiring thermal overload protection, such as cable or power transformer feeders.

Summary of Protection Functions

The relay thermal overload unit protects the motor against short- and long-term overloads. The maximum permissible continuous load depends on the setting value 1.

Normally this setting value is taken as the rated full load current (FLC) of the motor at an ambient temperature of 40°C. The motor can be overloaded for a short period of time if the motor is not loaded.

When the motor current increases to 1.05I under the above conditions, the thermal overload unit starts after a certain delay.

If the ambient temperature of the motor is below 40°C for a long period of time, the setting value I. can be set to .05...1.10 times the full load current (FLC) of the motor. 1.10 times.

The short-time overload phenomenon mainly occurs during the starting process of the motor. The motor is normally allowed to start twice under cold conditions and once under hot conditions.

One start is permitted under hot conditions, therefore, depending on the starting time of the motor, an integrating value t determining the characteristics of the thermal overload unit can be derived.

This value can be easily determined from the time/current graph in the hot state. t curve is selected from the starting current versus the corresponding starting time (with an appropriate margin).

The t-curve is selected from the starting current versus the corresponding starting time (with an appropriate margin). Using the same value of t, the total permissible starting time of the motor under cold conditions can be found from the cold curve.

As a rule of thumb, for two cold starts or one hot start, the t-value is set to 1.6...2.0 times the starting time of the motor. ...2.0 times.

The thermal overload pre-warning signal can warn the operator to reduce the load of the motor when thermal overload occurs, thus avoiding unnecessary thermal overload tripping.

This can avoid unnecessary thermal overload tripping. The setting value of the pre-warning signal can be individually set to a certain percentage of the thermal overload tripping value.

Therefore, by choosing the appropriate pre-warning signal setting value, the motor can be operated close to the thermal capacity limit value while avoiding tripping due to prolonged overload.

Every time the motor is started, the start-up monitoring unit monitors the thermal consumption of the motor, usually in accordance with the It formula.

Alternatively, a fixed time limit overcurrent can be used. The latter is mainly used for equipment with non-motor loads.

In either case, a speed switch signal such as that mounted on the motor shaft to distinguish between motor blocking and normal starting can be programmed into the relay to control the output trip command.

to control the output trip command. A high value overcurrent protection unit (current cut-off) for protection against short-circuits between motor windings and short-circuits between phases of feeder cables.

The current setting value can be set so that it is automatically doubled during start-up. Therefore, the setting value can be set lower than the motor starting current.

Normally it can be set as low as 0.75 times the motor starting current. In addition, an appropriate action time should be set to match.

In this way, when the motor is blocked during operation, the current interruption protection unit can ensure reliable operation.

When the motor is controlled by a contactor, the high value overcurrent protection unit should be blocked and the fuse should be used to protect against short circuits.

The non-directional earth fault unit detects earth faults in the motor and feeder circuits. In the neutral point directly grounded or through the low impedance grounding system, the CT can be connected to a residual ground fault.

The CT can be wired for residual current to obtain the zero sequence current, and the action time of the earth fault protection can usually be set to a smaller value, e.g. 50ms.

In circuits controlled by contactors, the line current can be set to exceed 4 (or 6.8) times the full load current I in the thermal overload unit.

The earth fault unit is blocked so that the contactor will not be damaged by the inability to break the high current and the fault current will be broken by the back-up fuse.

This blocking function is also used to prevent malfunctions caused by false zero sequence currents during start-up due to saturation of the CT on the circuit.

In order to obtain a high sensitivity, the earth fault current action value is generally rounded to 15...40% of the rated motor current. ...40% of the motor's rated current.

In networks where the neutral point is insulated or earthed via a high impedance, it is recommended to use feedthrough zero sequence current transformers.

The ratio of this type of transformer can be flexibly selected according to the size of the earth fault current and the sensitivity of the earth fault protection.

Due to the small input impedance of the relay, it is possible to use current transformers with very small ratios.

For example, the KOLMA zero sequence current transformer with a ratio of 10/1A is small, but it is generally recommended to use a zero sequence current transformer with a ratio of 50/1A or 100/1A or more.

The setting value of the ground fault unit is generally set to 5...30% of the value of the fully grounded (metallic grounding) fault current, and the value of the ground fault unit is generally set to 5...30% of the value of the fully grounded (metallic grounding) fault current. .30%, action time is 0.5.... .2 seconds.

Phase unbalance unit monitor system current unbalance condition well prevent motor damage due to serious system unbalance or single-phase operation.

The phase unbalance unit should ensure stability under heavy load conditions to prevent false operation, when the motor is running at less than full load current, it is allowed to have a larger degree of unbalance.

The action time of this unit is an inverse time limit characteristic. Dirt phase protection is an independent unit which will operate with a fixed delay of 600s when the phase sequence is wrong.

The unbalance and inverted phase protection units can be independently selected or withdrawn, e.g. the inverted phase unit can be withdrawn from use when the motor is allowed to operate in reverse phase sequence, so that there is no risk of the motor being damaged by a reversal of phase sequence.

In this case there will be no tripping due to motor reversal. The low-current unit is used for out-of-load protection of motors.

The unit is particularly suitable for equipment cooled by a constant flow of liquid, e.g. submersible pumps, where the cooling capacity of the motor is reduced when the flow is interrupted.

In this case the motor circuit will be tripped by the low current unit detecting the well. The start time totaliser is another measure to control the number of starts in a given period of time.

It can be set according to the permissible number of starts provided by the motor manufacturer.

The fault parameters recorded in the registers are very convenient and useful for fault analysis.

In addition, the continuous tracking of the motor start-up process and other parameters are extremely useful for monitoring the motor's operating conditions.

The serial communication interface allows all measurements and register parameters to be transferred to the control room or elsewhere in the most convenient way.